Papers on tree growth rate vs. longevity, live fast – die young

Forest carbon sink neutralized by pervasive growth-lifespan trade-offs (Brienen et al. 2020) [OPEN ACCESS]. “Land vegetation is currently taking up large amounts of atmospheric CO₂, possibly due to tree growth stimulation. Extant models predict that this growth stimulation will continue to cause a net carbon uptake this century. However, there are indications that increased growth rates may shorten trees′ lifespan and thus recent increases in forest carbon stocks may be transient due to lagged increases in mortality. Here we show that growth-lifespan trade-offs are indeed near universal, occurring across almost all species and climates. This trade-off is directly linked to faster growth reducing tree lifespan, and not due to covariance with climate or environment. Thus, current tree growth stimulation will, inevitably, result in a lagged increase in canopy tree mortality, as is indeed widely observed, and eventually neutralise carbon gains due to growth stimulation. Results from a strongly data-based forest simulator confirm these expectations. Extant Earth system model projections of global forest carbon sink persistence are likely too optimistic, increasing the need to curb greenhouse gas emissions.” Brienen, R.J.W., Caldwell, L., Duchesne, L. et al. Forest carbon sink neutralized by pervasive growth-lifespan trade-offs. Nat Commun 11, 4241 (2020). https://doi.org/10.1038/s41467-020-17966-z

Limited capacity of tree growth to mitigate the global greenhouse effect under predicted warming (Büntgen et al. 2019) [OPEN ACCESS]. “It is generally accepted that animal heartbeat and lifespan are often inversely correlated, however, the relationship between productivity and longevity has not yet been described for trees growing under industrial and pre-industrial climates. Using 1768 annually resolved and absolutely dated ring width measurement series from living and dead conifers that grew in undisturbed, high-elevation sites in the Spanish Pyrenees and the Russian Altai over the past 2000 years, we test the hypothesis of grow fast—die young. We find maximum tree ages are significantly correlated with slow juvenile growth rates. We conclude, the interdependence between higher stem productivity, faster tree turnover, and shorter carbon residence time, reduces the capacity of forest ecosystems to store carbon under a climate warming-induced stimulation of tree growth at policy-relevant timescales.” Büntgen, U., Krusic, P.J., Piermattei, A. et al. Limited capacity of tree growth to mitigate the global greenhouse effect under predicted warming. Nat Commun 10, 2171 (2019). https://doi.org/10.1038/s41467-019-10174-4

Temporal declines in tree longevity associated with faster lifetime growth rates in boreal forests (Searle & Chen, 2018) [OPEN ACCESS]. “Global change has been linked to significant increases in tree mortality in the world’s forests. Reduced tree longevity through increased growth rates has been suggested as one of the mechanisms responsible for the temporal increases in tree mortality, but this idea has not been directly tested. Here we explicitly defined two testable hypotheses: (i) the probability of ageing driven tree mortality increases with global change and (ii) the mortality probability associated with global change is higher for faster growing trees. To test these hypotheses, we examined the temporal changes of tree mortality probability in 539 permanent sample plots monitored from 1960–2009, with ages greater than 100 years at initial censuses, across the boreal region of Alberta, Canada. As expected, we found an overall temporal increase in tree mortality probability, indicating a loss in tree longevity with global change. We also found that trees with faster lifetime growth rates experienced higher temporal increases in mortality probability compared to slower growing trees. An analysis of the responses of tree mortality probability to increasing atmospheric carbon dioxide and temperature and decreases in water availability indicated that increasing atmospheric carbon dioxide and decreasing water availability were the major drivers of declining longevity. Our results suggest that tree longevity may further decline with the expected increase of atmospheric carbon dioxide and decreasing water availability in the region.” Eric B Searle and Han Y H Chen 2018 Environ. Res. Lett. 13 125003. https://doi.org/10.1088/1748-9326/aaea9e

The longevity of broadleaf deciduous trees in Northern Hemisphere temperate forests: insights from tree-ring series (Di Filippo et al. 2015) [OPEN ACCESS]. “Understanding the factors controlling the expression of longevity in trees is still an outstanding challenge for tree biologists and forest ecologists. We gathered tree-ring data and literature for broadleaf deciduous (BD) temperate trees growing in closed-canopy old-growth (OG) forests in the Northern Hemisphere to explore the role of geographic patterns, climate variability, and growth rates on longevity. Our pan-continental analysis, covering 25 species from 12 genera, showed that 300–400 years can be considered a baseline threshold for maximum tree lifespan in many temperate deciduous forests. Maximum age varies greatly in relation to environmental features, even within the same species. Tree longevity is generally promoted by reduced growth rates across large genetic differences and environmental gradients. We argue that slower growth rates, and the associated smaller size, provide trees with an advantage against biotic and abiotic disturbance agents, supporting the idea that size, not age, is the main constraint to tree longevity. The oldest trees were living most of their life in subordinate canopy conditions and/or within primary forests in cool temperate environments and outside major storm tracks. Very old trees are thus characterized by slow growth and often live in forests with harsh site conditions and infrequent disturbance events that kill much of the trees. Temperature inversely controls the expression of longevity in mesophilous species (Fagus spp.), but its role in Quercus spp. is more complex and warrants further research in disturbance ecology. Biological, ecological, and historical drivers must be considered to understand the constraints imposed to longevity within different forest landscapes.” Alfredo Di Filippo, Neil Pederson, Michele Baliva, Michele Brunetti, Anna Dinella, Keiko Kitamura, Hanns D. Knapp, Bartolomeo Schirone, Gianluca Piovesan (2015). Front. Ecol. Evol., Sec. Paleoecology 3(15 May 2015). https://doi.org/10.3389/fevo.2015.00046

Slow lifelong growth predisposes Populus tremuloides trees to mortality (Ireland et al. 2014) [FULL TEXT]. “Widespread dieback of aspen forests, sometimes called sudden aspen decline, has been observed throughout much of western North America, with the highest mortality rates in the southwestern United States. Recent aspen mortality has been linked to drought stress and elevated temperatures characteristic of conditions expected under climate change, but the role of individual aspen tree growth patterns in contributing to recent tree mortality is less well known. We used tree-ring data to investigate the relationship between an individual aspen tree’s lifetime growth patterns and mortality. Surviving aspen trees had consistently higher average growth rates for at least 100 years than dead trees. Contrary to observations from late successional species, slow initial growth rates were not associated with a longer lifespan in aspen. Aspen trees that died had slower lifetime growth and slower growth at various stages of their lives than those that survived. Differences in average diameter growth between live and dead trees were significant (α = 0.05) across all time periods tested. Our best logistical model of aspen mortality indicates that younger aspen trees with lower recent growth rates and higher frequencies of abrupt growth declines had an increased risk of mortality. Our findings highlight the need for species-specific mortality functions in forest succession models. Size-dependent mortality functions suitable for late successional species may not be appropriate for species with different life history strategies. For some early successional species, like aspen, slow growth at various stages of the tree’s life is associated with increased mortality risk.” Ireland, K.B., Moore, M.M., Fulé, P.Z. et al. Slow lifelong growth predisposes Populus tremuloides trees to mortality. Oecologia 175, 847–859 (2014). https://doi.org/10.1007/s00442-014-2951-5

Extreme longevity in trees: live slow, die old? (Issartel & Coiffard, 2011). “We have examined the extreme longevity displayed by trees in relation to a theory mainly developed in animals, namely, the controversial rate of living (ROL) theory of aging which proposes that longevity is negatively correlated to metabolic rate. Plant metabolism implies respiration and photosynthesis; both are susceptible to negatively impact longevity. The relationship between longevity and metabolism was studied in leaves and stems of several species with the aim of challenging the ROL theory in trees. Leaf and stem life spans were found to be highly correlated to metabolism (R ² = 0.97), and stems displayed a much lower metabolism than leaves. Analysis of covariance (ANCOVA), with metabolism as the covariate, revealed no difference between mean leaf and stem life spans, which would appear to conform to the expectations of the ROL theory. Consequently, the extremely high longevity of trees may be explained by the lower metabolism displayed by the stems. These results clearly reflect different energy allocation and energy expenditure rate strategies between leaves and stems, which may result in different senescence rates (and life spans) in these organs. They also suggest that, in contrast to animals, the ROL theory of aging may apply to woody plants at the organ level, thereby opening a promising new line of research to guide future studies on plant senescence.” Issartel, J., Coiffard, C. Extreme longevity in trees: live slow, die old?. Oecologia 165, 1–5 (2011). https://doi.org/10.1007/s00442-010-1807-x

Will the CO2 fertilization effect in forests be offset by reduced tree longevity? (Bugmann & Bigler, 2010) [FULL TEXT]. “Experimental studies suggest that tree growth is stimulated in a greenhouse atmosphere, leading to faster carbon accumulation (i.e., a higher rate of gap filling). However, higher growth may be coupled with reduced longevity, thus leading to faster carbon release (i.e., a higher rate of gap creation). The net effect of these two counteracting processes is not known. We quantify this net effect on aboveground carbon stocks using a novel combination of data sets and modeling. Data on maximum growth rate and maximum longevity of 141 temperate tree species are used to derive a relationship between growth stimulation and changes in longevity. We employ this relationship to modify the respective parameter values of tree species in a forest succession model and study aboveground biomass in a factorial design of growth stimulation × reduced maximum longevity at multiple sites along a climate gradient from the cold to the dry treeline. The results show that (1) any growth stimulation at the tree level leads to a disproportionately small increase of stand biomass due to negative feedback effects, even in the absence of reduced longevity; (2) a reduction of tree longevity tends to offset the growth-related biomass increase; at the most likely value of reduced longevity, the net effect is very close to zero in most multi- and single-species simulations; and (3) when averaging the response across all sites to mimic a “landscape-level” response, the net effect is close to zero. Thus, it is important to consider ecophysiological responses with their linkage to demographic processes in forest trees if one wishes to avoid erroneous inference at the ecosystem level. We conclude that any CO₂ fertilization effect is quite likely to be offset by an associated reduction in the longevity of forest trees, thus strongly reducing the carbon mitigation potential of temperate forests.” Bugmann, H., Bigler, C. Will the CO₂ fertilization effect in forests be offset by reduced tree longevity?. Oecologia 165, 533–544 (2011). https://doi.org/10.1007/s00442-010-1837-4

Functional traits and the growth–mortality trade-off in tropical trees (Wright et al. 2010) [FULL TEXT]. “A trade-off between growth and mortality rates characterizes tree species in closed canopy forests. This trade-off is maintained by inherent differences among species and spatial variation in light availability caused by canopy-opening disturbances. We evaluated conditions under which the trade-off is expressed and relationships with four key functional traits for 103 tree species from Barro Colorado Island, Panama. The trade-off is strongest for saplings for growth rates of the fastest growing individuals and mortality rates of the slowest growing individuals (r² = 0.69), intermediate for saplings for average growth rates and overall mortality rates (r² = 0.46), and much weaker for large trees (r² ≤ 0.10). This parallels likely levels of spatial variation in light availability, which is greatest for fast- vs. slow-growing saplings and least for large trees with foliage in the forest canopy. Inherent attributes of species contributing to the trade-off include abilities to disperse, acquire resources, grow rapidly, and tolerate shade and other stresses. There is growing interest in the possibility that functional traits might provide insight into such ecological differences and a growing consensus that seed mass (SM), leaf mass per area (LMA), wood density (WD), and maximum height (H_max) are key traits among forest trees. Seed mass, LMA, WD, and H_max are predicted to be small for light-demanding species with rapid growth and mortality and large for shade-tolerant species with slow growth and mortality. Six of these trait–demographic rate predictions were realized for saplings; however, with the exception of WD, the relationships were weak (r² < 0.1 for three and r² < 0.2 for five of the six remaining relationships). The four traits together explained 43–44% of interspecific variation in species positions on the growth–mortality trade-off; however, WD alone accounted for >80% of the explained variation and, after WD was included, LMA and H_max made insignificant contributions. Virtually the full range of values of SM, LMA, and H_max occurred at all positions on the growth–mortality trade-off. Although WD provides a promising start, a successful trait-based ecology of tropical forest trees will require consideration of additional traits.” Wright, S.J., Kitajima, K., Kraft, N.J.B., Reich, P.B., Wright, I.J., Bunker, D.E., Condit, R., Dalling, J.W., Davies, S.J., Díaz, S., Engelbrecht, B.M.J., Harms, K.E., Hubbell, S.P., Marks, C.O., Ruiz-Jaen, M.C., Salvador, C.M. and Zanne, A.E. (2010), Functional traits and the growth–mortality trade-off in tropical trees. Ecology, 91: 3664-3674. https://doi.org/10.1890/09-2335.1

Increased early growth rates decrease longevities of conifers in subalpine forests (Bigler & Veblen, 2009) [FULL TEXT]. “For trees, fast growth rates and large size seem to be a fitness benefit because of increased competitiveness, attainment of reproductive size earlier, reduction of generation times, and increased short-term survival chances. However, fast growth rates and large size entail reduced investment in defenses, lower wood density and mechanical strength, increased hydraulic resistance as well as problems with down-regulation of growth during periods of stress, all of which may decrease tree longevity. In this study, we investigated the relationship between longevity and growth rates of trees and quantified effects of spatial environmental variation (elevation, slope steepness, aspect, soil depth) on tree longevity. Radial growth rates and longevities were determined from tree-ring samples of 161 dead trees from three conifer species in subalpine forests of the Colorado Rocky Mountains (Abies lasiocarpa, Picea engelmannii) and the Swiss Alps (Picea abies). For all three species, we found an apparent tradeoff between growth rate to the age of 50 years and longevity (i.e. fast early growth is associated with decreased longevity). This association was particularly pronounced for larger P. engelmannii and P. abies, which attained canopy size, however, there were also significant effects for smaller P. engelmannii and P. abies. For the more shade-tolerant A. lasiocarpa, tree size did not have any effect. Among the abiotic variables tested only northerly aspect significantly favored longevity of A. lasiocarpa and P. engelmannii. Trees growing on south-facing aspects probably experience greater water deficits leading to premature tree death, and/or shorter life spans may reflect shorter fire intervals on these more xeric aspects. Empirical evidence from other studies has shown that global warming affects growth rates of trees over large spatial and temporal scales. For moist-cool subalpine forests, we hypothesize that the higher growth rates associated with global warming may in turn result in reduced tree longevity and more rapid turnover rates.” Bigler, C. and Veblen, T.T. (2009), Increased early growth rates decrease longevities of conifers in subalpine forests. Oikos, 118: 1130-1138. https://doi.org/10.1111/j.1600-0706.2009.17592.x

Age class, longevity and growth rate relationships: protracted growth increases in old trees in the eastern United States (Johnson & Abrams, 2009) [OPEN ACCESS]. “This study uses data from the International Tree-Ring Data Bank website and tree cores collected in the field to explore growth rate (basal area increment, BAI) relationships across age classes (from young to old) for eight tree species in the eastern US. These species represent a variety of ecological traits and include those in the genera Populus, Quercus, Pinus, Tsuga and Nyssa. We found that most trees in all age classes and species exhibit an increasing BAI throughout their lives. This is particularly unusual for trees in the older age classes that we expected to have declining growth in the later years, as predicted by physiological growth models. There exists an inverse relationship between growth rate and increasing age class. The oldest trees within each species have consistently slow growth throughout their lives, implying an inverse relationship between growth rate and longevity. Younger trees (< 60 years of age) within each species are consistently growing faster than the older trees when they are of the same age resulting from a higher proportion of fast-growing trees in these young age classes. Slow, but increasing, BAI in the oldest trees in recent decades is a continuation of their growth pattern established in previous centuries. The fact that they have not shown a decreasing growth rate in their old age contradicts physiological growth models and may be related to the stimulatory effects of global change phenomenon (climate and land-use history).” Sarah E. Johnson, Marc D. Abrams, Age class, longevity and growth rate relationships: protracted growth increases in old trees in the eastern United States, Tree Physiology, Volume 29, Issue 11, November 2009, Pages 1317–1328, https://doi.org/10.1093/treephys/tpp068

Relationships between radial growth rates and lifespan within North American tree species (Black et al. 2008) [FULL TEXT]. “We conducted a meta-analysis of tree-ring data to quantify relationships between growth and lifespan in 4 North American tree species: Tsuga canadensis, Quercus alba, Pinus ponderosa, and Pseudotsuga menziesii. Data sets were compiled from across the range of each species and included a total of 14 341 measured time series. For each species we calculated the age at which each tree was sampled and pooled all trees into 50-y bins. Within each of these 50-y bins, we calculated mean ring width and mean basal area increment in 50-y intervals according to cambial age. Thus, ring widths formed during the same time period in the trees’ life stage could be compared across trees sampled at increasing ages. In all 4 species the longest-lived trees experienced slower growth rates than trees sampled at relatively young ages. Furthermore, long-lived trees with slow growth rates appear to mix with shorter-lived, fast-growing trees in the same forests. Such a relationship between growth and lifespan within species may be an important component of biodiversity that holds implications for old-growth forest development and long-term management.” Bryan A. Black, Jim J. Colbert & Neil Pederson (2008) Relationships between radial growth rates and lifespan within North American tree species, Écoscience, 15:3, 349-357, https://doi.org/10.2980/15-3-3149

Papers on how longwave radiation warms oceans

The Impact of Wind Gusts on the Ocean Thermal Skin Layer – Zappa et al. (2019) “The thermodynamic and emissive properties of the ocean thermal skin layer are crucial contributors to air‐sea heat flux. In order to properly observe ocean surface temperature without disturbing any delicate fluid mechanical processes, thermal infrared imaging is often used. However, wind impacting the ocean surface complicates the extraction of meaningful information from thermal imagery; this is especially true for transient forcing phenomena such as wind gusts. Here, we describe wind gust‐water surface interaction through its impact on skin layer thermal and emissive properties. Two key physical processes are identified: (1) the growth of centimeter‐scale wind waves, which increases interfacial emissivity, and (2) microscale wave breaking and shear, which mix the cool skin layer with warmer millimeter‐depth water and increase the skin temperature. As more observations are made of air‐sea interaction under transient forcing, the full consideration of these processes becomes increasingly important.” Zappa, C. J., Laxague, N. J. M., Brumer, S. E., & Anderson, S. P. (2019). The impact of wind gusts on the ocean thermal skin layer. Geophysical Research Letters, 46, 11301– 11309. https://doi.org/10.1029/2019GL083687. [FULL TEXT]

The Response of the Ocean Thermal Skin Layer to Variations in Incident Infrared Radiation – Wong & Minnett (2018) “Ocean warming trends are observed and coincide with the increase in concentrations of greenhouse gases in the atmosphere resulting from human activities. At the ocean surface, most of the incoming infrared (IR) radiation is absorbed within the top micrometers of the ocean’s surface where the thermal skin layer (TSL) exists. Thus, the incident IR radiation does not directly heat the upper few meters of the ocean. This paper investigates the physical mechanism between the absorption of IR radiation and its effect on heat transfer at the air‐sea boundary. The hypothesis is that given the heat lost through the air‐sea interface is controlled by the TSL, the TSL adjusts in response to variations in incident IR radiation to maintain the surface heat loss. This modulates the flow of heat from below and hence controls upper ocean heat content. This hypothesis is tested using the increase in incoming longwave radiation from clouds and analyzing vertical temperature profiles in the TSL retrieved from sea‐surface emission spectra. The additional energy from the absorption of increasing IR radiation adjusts the curvature of the TSL such that the upward conduction of heat from the bulk of the ocean into the TSL is reduced. The additional energy absorbed within the TSL supports more of the surface heat loss. Thus, more heat beneath the TSL is retained leading to the observed increase in upper ocean heat content.” Wong, E. W., & Minnett, P. J. (2018). The response of the ocean thermal skin layer to variations in incident infrared radiation. Journal of Geophysical Research: Oceans, 123, 2475‐ 2493. https://doi.org/10.1002/2017JC013351. [FULL TEXT]

Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface – Liu et al. (1979) “A model is developed for the marine atmospheric surface layer including the interfacial sublayers on both sides of the air-sea interface where molecular constraints on transports are important. Flux-profile relations which are based on the postulation of intermittent renewal of the surface fluid aye matched to the logarithmic profiles and compared with both field and laboratory measurements. These relations enable numerical determination of air-sea exchanges of momentum, heat and water vapor (or bulk transfer coefficients) employing the bulk parameters of mean wind speed, temperature and humidity at a certain height in the atmospheric surface layer, and the water temperature. With increasing wind speed, the flow goes from smooth to rough and the bulk transfer coefficient for momentum also increases. The increase in roughness is associated with increasing wave height which in the present model results in sheltering at the wave troughs. Due to the decrease in turbulent transports, the transfer coefficients of heat and water vapor decrease slightly with wind speed after the wind speed exceeds a certain value. The bulk transfer coefficients are also found to decrease with increasing stability. If the “bucket temperature” which typically gives the water temperature a few centimeters below the surface is used, rather than the interfacial temperature, erroneous results may be obtained when the air-sea temperature difference is small. By including the effects of stability and interfacial conditions in bulk parameterization, the model provides a way to account for physical conditions which are known to affect air-sea exchanges.” Liu, W. T., Katsaros, K. B., & Businger, J. A. (1979). Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface, Journal of Atmospheric Sciences, 36(9), 1722-1735. https://doi.org/10.1175/1520-0469(1979)036<1722:BPOASE>2.0.CO;2. [FULL TEXT]

Heat thermal structure in the interfacial boundary layer measured in an open tank of water in turbulent free convection – Katsaros et al. (1977) “The thermal structure in the boundary layer and its relation to the heat flux from the cooling and evaporating surface of a deep tank of water are investigated. When a deep layer of water in contact with still air above loses heat to the air, the cooled water in a region just under the surface converges along lines and then plunges down in sheets. These sheets of falling water dissipate as they move into the body of the water, which is in turbulent motion. The vertical profiles of the horizontally averaged temperature and its standard deviation agree fairly closely with theoretical profiles based on time averages of the solution to the heat diffusion equation. The differences between observed and thus predicted profile shapes are consistent with the expected effects of the falling cold thermals and the warm return flow, which are neglected in the theories. The profiles of the standard deviation have large values up to the interface and lie between predictions based on boundary conditions of constant surface temperature and constant heat flux, in keeping with the experimental conditions. The relation between the net heat flux and the temperature difference across the boundary layer is given in non-dimensional form by N = 0[sdot ]156R^{0[sdot ]33}, which is in good agreement with the asymptotic similarity prediction N [vprop ] R1/3 but lower than theoretical calculations of the upper bound of N vs. R.” Katsaros, K., Liu, W., Businger, J., & Tillman, J. (1977). Heat thermal structure in the interfacial boundary layer measured in an open tank of water in turbulent free convection. Journal of Fluid Mechanics, 83(2), 311-335. doi:10.1017/S0022112077001219. [FULL TEXT]

Air-sea bulk transfer coefficients in diabatic conditions – Kondo (1975) “On the basis of recent data for the roughness Reynolds number of the sea surface, and using the Owen-Thomson theory on the transfers of heat and mass between a rough surface and the flow above it, the bulk transfer coefficients of the sea surface have been estimated. For a reference height of 10 m, the neutral-lapse transfer coefficient for water vapor is larger by only a few percent than that for sensible heat. When the wind speed at the 10-m height is u ₁₀>3 m s⁻¹, the coefficient for sensible heat C _H is larger by about 10% than that for momentum C _D . For u ₁₀<5 m s⁻¹, however, the value of C _D exceeds the value of C _H , and for u ₁₀=15 m s⁻¹ it is shown that C _H ≈0.8C _D . It may be also proposed that 10³ C _D =1.11 to 1.70, 10³ C _E =1.18 to 1.30, and 10³ C _H =1.15 to 1.26 for a range of u ₁₀=4 to 20 m s⁻¹. A plot of diabatic transfer coefficients versus wind speed is obtained by using a parameter of the sea-air temperature difference. For practical purposes, the coefficients are approximated by empirical formulae.” Kondo, J. Air-sea bulk transfer coefficients in diabatic conditions. Boundary-Layer Meteorol 9, 91–112 (1975). https://doi.org/10.1007/BF00232256.

Papers on COVID-19 and climate change

Quantifying the influence of short-term emission reductions on climate (Fyfe et al. 2021). “These estimates reveal the modest impact that temporary emission reductions associated with the COVID-19 pandemic will have on global and regional climate. Our simulations suggest that the impact of carbon dioxide and aerosol emission reductions is actually a temporary enhancement in warming rate. However, our results demonstrate that even large emission reductions applied for a short duration have only a small and likely undetectable impact.” J. C. Fyfe, V. Kharin, N. Swart, G. M. Flato, M. Sigmond, N. P. Gillett (2021). Science Advances 7(10):eabf7133.
https://doi.org/10.1126/sciadv.abf7133

The Climate Response to Emissions Reductions Due to COVID-19: Initial Results From CovidMIP (Jones et al. 2021). “We find model consensus on reduced aerosol amounts (particularly over southern and eastern Asia) and associated increases in surface shortwave radiation levels. However, any impact on near-surface temperature or rainfall during 2020–2024 is extremely small and is not detectable in this initial analysis.” Jones, C. D., Hickman, J. E., Rumbold, S. T., Walton, J., Lamboll, R. D., Skeie, R. B., et al. (2021). The climate response to emissions reductions due to COVID-19: Initial results from CovidMIP. Geophysical Research Letters, 48, e2020GL091883. https://doi.org/10.1029/2020GL091883

Climate Impacts of COVID‐19 Induced Emission Changes (Gettelman et al. 2021). “The average overall Effective Radiative Forcing (ERF) peaks at +0.29 ± 0.15 Wm⁻² in spring 2020.” … “However, the aerosol changes are the largest contribution to radiative forcing and temperature changes as a result of COVID‐19 affected emissions, larger than ozone, CO₂ and contrail effects.” Gettelman, A., Lamboll, R., Bardeen, C. G., Forster, P. M., & Watson‐Parris, D. (2021). Climate impacts of COVID‐19 induced emission changes. Geophysical Research Letters, 48, e2020GL091805. https://doi.org/10.1029/2020GL091805

Current and future global climate impacts resulting from COVID-19 (Forster et al. 2020). “As a result, we estimate that the direct effect of the pandemic-driven response will be negligible, with a cooling of around 0.01 ± 0.005 °C by 2030 compared to a baseline scenario that follows current national policies.” Forster, P.M., Forster, H.I., Evans, M.J. et al. Current and future global climate impacts resulting from COVID-19. Nat. Clim. Chang. 10, 913–919 (2020). https://doi.org/10.1038/s41558-020-0883-0

Satellite-based estimates of decline and rebound in China’s CO₂ emissions during COVID-19 pandemic (Zheng et al. 2020). “Between January and April 2020, China’s CO₂ emissions fell by 11.5% compared to the same period in 2019, but emissions have since rebounded to pre-pandemic levels before the coronavirus outbreak at the beginning of January 2020 owing to the fast economic recovery in provinces where industrial activity is concentrated.” Bo Zheng, Guannan Geng, Philippe Ciais, Steven J. Davis, Randall V. Martin et al. (2020). Science Advances 6(49):eabd4998. DOI: 10.1126/sciadv.abd4998

Fast Climate Responses to Aerosol Emission Reductions During the COVID‐19 Pandemic (Yang et al. 2020). “Assuming emission changes during lockdown, back‐to‐work and post‐lockdown stages of COVID‐19, climate model simulations show a surface warming over continental regions of the Northern Hemisphere. In January–March, there was an anomalous warming of 0.05–0.15 K in eastern China, and the surface temperature increase was 0.04–0.07 K in Europe, eastern United States, and South Asia in March–May.” Yang, Y., Ren, L., Li, H., Wang, H., Wang, P., Chen, L., et al. (2020). Fast climate responses to aerosol emission reductions during the COVID‐19 pandemic. Geophysical Research Letters, 47, e2020GL089788. https://doi.org/10.1029/2020GL089788

Minimal Climate Impacts From Short‐Lived Climate Forcers Following Emission Reductions Related to the COVID‐19 Pandemic (Weber et al. 2020). “Overall, the changes in ozone and aerosol direct effects (neglecting aerosol‐cloud interactions which were statistically insignificant but whose response warrants future investigation) yield a radiative forcing of −33 to −78 mWm⁻².” Weber, J., Shin, Y. M., Staunton Sykes, J., Archer‐Nicholls, S., Abraham, N. L., & Archibald, A. T. (2020). Minimal climate impacts from short‐lived climate forcers following emission reductions related to the COVID‐19 pandemic. Geophysical Research Letters, 47, e2020GL090326. https://doi.org/10.1029/2020GL090326

Near-real-time monitoring of global CO₂ emissions reveals the effects of the COVID-19 pandemic (Liu et al. 2020). “The key result is an abrupt 8.8% decrease in global CO₂ emissions (−1551 Mt CO₂) in the first half of 2020 compared to the same period in 2019. The magnitude of this decrease is larger than during previous economic downturns or World War II. The timing of emissions decreases corresponds to lockdown measures in each country. By July 1st, the pandemic’s effects on global emissions diminished as lockdown restrictions relaxed and some economic activities restarted,…” Liu, Z., Ciais, P., Deng, Z. et al. Near-real-time monitoring of global CO₂ emissions reveals the effects of the COVID-19 pandemic. Nat Commun 11, 5172 (2020). https://doi.org/10.1038/s41467-020-18922-7

Temporary reduction in daily global CO₂ emissions during the COVID-19 forced confinement (Le Quéré et al. 2020). “Daily global CO₂ emissions decreased by –17% (–11 to –25% for ±1σ) by early April 2020 compared with the mean 2019 levels, just under half from changes in surface transport. At their peak, emissions in individual countries decreased by –26% on average.” Le Quéré, C., Jackson, R.B., Jones, M.W. et al. Temporary reduction in daily global CO₂ emissions during the COVID-19 forced confinement. Nat. Clim. Chang. 10, 647–653 (2020). https://doi.org/10.1038/s41558-020-0797-x

Papers on Indian Ocean Dipole (IOD) and climate change

This is a list of papers on Indian Ocean Dipole (IOD) and climate change. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Indo-Pacific Climate Modes in Warming Climate: Consensus and Uncertainty Across Model Projections – Zheng (2019)
“Purpose of Review: Understanding the changes in climate variability in a warming climate is crucial for reliable projections of future climate change. This article reviews the recent progress in studies of how climate modes in the Indo-Pacific respond to greenhouse warming, including the consensus and uncertainty across climate models. Recent Findings: Recent studies revealed a range of robust changes in the properties of climate modes, often associated with the mean state changes in the tropical Indo-Pacific. In particular, the intermodel diversity in the ocean warming pattern is a prominent source of uncertainty in mode changes. The internal variability also plays an important role in projected changes in climate modes. Summary: Model biases and intermodel variability remain major challenges for reducing uncertainty in projecting climate mode changes in warming climate. Improved models and research linking simulated present-day climate and future changes are essential for reliable projections of climate mode changes. In addition, large ensembles should be used for each model to reduce the uncertainty from internal variability and isolate the forced response to global warming.”
Zheng, X. Indo-Pacific Climate Modes in Warming Climate: Consensus and Uncertainty Across Model Projections. Curr Clim Change Rep 5, 308–321 (2019) doi:10.1007/s40641-019-00152-9. [FULL TEXT]

Disentangling the Changes in the Indian Ocean Dipole–Related SST and Rainfall Variability under Global Warming in CMIP5 Models – Huang et al. (2019)
“This study disentangles the changes in Indian Ocean (IO) dipole (IOD)-related SST and rainfall variability under global warming projected by the RCP8.5 runs in 29 CMIP5 models. The IOD rainfall changes consist of the thermodynamic component due to the surface moisture increase and the dynamic component due to the changes in IOD-related circulation. The IOD circulation changes are dominated by the IOD SST changes, which were further clarified using the amplitude and structural decomposition. The amplitudes of IOD SST and circulation are both decreased at rates of around 7.2% and 13.7% °C⁻¹, respectively. The structural changes in IOD SST and circulation show a pattern with increases from the eastern to the western coast of the equatorial IO, similar to the pattern of so-called extreme IOD events in previous studies. Disentangling previous mechanisms and projections, we conclude that the increased atmospheric stability suppresses the amplitudes in IOD SST and circulation, whereas the positive IOD (pIOD)-like mean-state SST changes, leading to greater warming in the west than the east, mainly alter the structure of IOD SST and circulation. Both the amplitude and structural changes in the IOD SST and circulation are robust among the CMIP5 models, but their distinct patterns and out-of-step changes lead to an uncertain projection of IOD changes defined by the dipole mode index or EOF analysis in previous studies. Furthermore, the structural changes, dominated by the pIOD-like mean-state SST changes, are significantly correlated with the historical IOD amplitude among the models. Considering the commonly overestimated IOD amplitude as an emergent constraint, the structural changes in IOD SST and circulation should not be as robust as the original multimodel projection.”
Huang, P., X. Zheng, and J. Ying, 2019: Disentangling the Changes in the Indian Ocean Dipole–Related SST and Rainfall Variability under Global Warming in CMIP5 Models. J. Climate, 32, 3803–3818, https://doi.org/10.1175/JCLI-D-18-0847.1. [FULL TEXT]

Influence of internal climate variability on Indian Ocean Dipole properties – Ng et al. (2018)
“The Indian Ocean Dipole (IOD) is the dominant mode of interannual variability over the tropical Indian Ocean (IO) and its future changes are projected to impact the climate and weather of Australia, East Africa, and Indonesia. Understanding the response of the IOD to a warmer climate has been largely limited to studies of individual coupled general circulation models or multi-model ensembles. This has provided valuable insight into the IOD’s projected response to increasing greenhouse gases but has limitations in accounting for the role of internal climate variability. Using the Community Earth System Model Large Ensemble (CESM-LE), the IOD is examined in thirty-five present-day and future simulations to determine how internal variability influences properties of the IOD and their response to a warmer climate. Despite small perturbations in the initial conditions as the only difference between ensemble members, significant relationships between the mean state of the IO and the IOD arise, leading to a spread in the projected IOD responses to increasing greenhouse gases. This is driven by the positive Bjerknes feedback, where small differences in mean thermocline depth, which are caused by internal climate variability, generate significant variations in IOD amplitude, skewness, and the climatological zonal sea surface temperature gradient.”
Ng, B., Cai, W., Cowan, T. et al. Influence of internal climate variability on Indian Ocean Dipole properties. Sci Rep 8, 13500 (2018) doi:10.1038/s41598-018-31842-3. [FULL TEXT]

Uncertainty in Indian Ocean Dipole response to global warming: the role of internal variability – Hui & Zheng (2018)
“The Indian Ocean Dipole (IOD) is one of the leading modes of interannual sea surface temperature (SST) variability in the tropical Indian Ocean (TIO). The response of IOD to global warming is quite uncertain in climate model projections. In this study, the uncertainty in IOD change under global warming, especially that resulting from internal variability, is investigated based on the community earth system model large ensemble (CESM-LE). For the IOD amplitude change, the inter-member uncertainty in CESM-LE is about 50% of the intermodel uncertainty in the phase 5 of the coupled model intercomparison project (CMIP5) multimodel ensemble, indicating the important role of internal variability in IOD future projection. In CESM-LE, both the ensemble mean and spread in mean SST warming show a zonal positive IOD-like (pIOD-like) pattern in the TIO. This pIOD-like mean warming regulates ocean-atmospheric feedbacks of the interannual IOD mode, and weakens the skewness of the interannual variability. However, as the changes in oceanic and atmospheric feedbacks counteract each other, the inter-member variability in IOD amplitude change is not correlated with that of the mean state change. Instead, the ensemble spread in IOD amplitude change is correlated with that in ENSO amplitude change in CESM-LE, reflecting the close inter-basin relationship between the tropical Pacific and Indian Ocean in this model.”
Hui, C., Zheng, X. Uncertainty in Indian Ocean Dipole response to global warming: the role of internal variability. Clim Dyn 51, 3597–3611 (2018) doi:10.1007/s00382-018-4098-2.

Assessing the Impact of Model Biases on the Projected Increase in Frequency of Extreme Positive Indian Ocean Dipole Events – Wang et al. (2017)
“For many generations, models simulate an Indian Ocean dipole (IOD) that is overly large in amplitude. The possible impact of this systematic bias on climate projections, including a projected frequency increase in extreme positive IOD (pIOD) using a rainfall-based definition, has attracted attention. In particular, a recent study suggests that the increased frequency is an artifact of the overly large IOD amplitude. In contrast, here the opposite is found. Through intermodel ensemble regressions, the present study shows that models producing a high frequency in the present-day climate generate a small future frequency increase. The frequency is associated with the mean equatorial west-minus-east sea surface temperature (SST) gradient: the greater the gradient, the greater the frequency because it is easier to shift convection to the west, which characterizes an extreme pIOD. A greater present-day gradient is associated with a present-day shallower thermocline, lower SSTs, and lower rainfall in the eastern equatorial Indian Ocean (EEIO). Because there is an inherent limit for a maximum rainfall reduction and for the impact on surface cooling by a shallowing of an already shallow mean EEIO thermocline, there is a smaller increase in frequency in models with a shallower present-day EEIO thermocline. Given that a bias of overly shallow EEIO thermocline and overly low EEIO SSTs and rainfall is common in models, the future frequency increase should be underestimated, opposite to an implied overestimation resulting from the overly large IOD amplitude bias. Therefore, correcting the projected frequency from a single bias, without considering other biases that are present, is not appropriate and should be avoided.”
Wang, G., W. Cai, and A. Santoso, 2017: Assessing the Impact of Model Biases on the Projected Increase in Frequency of Extreme Positive Indian Ocean Dipole Events. J. Climate, 30, 2757–2767, https://doi.org/10.1175/JCLI-D-16-0509.1. [FULL TEXT]

A Robust but Spurious Pattern of Climate Change in Model Projections over the Tropical Indian Ocean – Li et al. (2016)
“Climate models consistently project reduced surface warming over the eastern equatorial Indian Ocean (IO) under increased greenhouse gas (GHG) forcing. This IO dipole (IOD)-like warming pattern, regarded as robust based on consistency among models by the new Intergovernmental Panel on Climate Change (IPCC) report, results in a large increase in the frequency of extreme positive IOD (pIOD) events, elevating the risk of climate and weather disasters in the future over IO rim countries. These projections, however, do not consider large model biases in both the mean state and interannual IOD variance. In particular, a “present–future relationship” is identified between the historical simulations and representative concentration pathway (RCP) 8.5 experiments from phase 5 of the Coupled Model Intercomparison Project (CMIP5) multimodel ensemble: models with an excessive IOD amplitude bias tend to project a strong IOD-like warming pattern in the mean and a large increase in extreme pIOD occurrences under increased GHG forcing. This relationship links the present simulation errors to future climate projections, and is also consistent with our understanding of Bjerknes ocean–atmosphere feedback. This study calibrates regional climate projections by using this present–future relationship and observed IOD amplitude. The results show that the projected IOD-like pattern of mean changes and frequency increase of extreme pIOD events are largely artifacts of model errors and unlikely to emerge in the future. These results illustrate that a robust projection may still be biased and it is important to consider the model bias effect.”
Li, G., S. Xie, and Y. Du, 2016: A Robust but Spurious Pattern of Climate Change in Model Projections over the Tropical Indian Ocean. J. Climate, 29, 5589–5608, https://doi.org/10.1175/JCLI-D-15-0565.1. [FULL TEXT]

Monsoon-Induced Biases of Climate Models over the Tropical Indian Ocean – Li et al. (2015)
“Long-standing biases of climate models limit the skills of climate prediction and projection. Overlooked are tropical Indian Ocean (IO) errors. Based on the phase 5 of the Coupled Model Intercomparison Project (CMIP5) multimodel ensemble, the present study identifies a common error pattern in climate models that resembles the IO dipole (IOD) mode of interannual variability in nature, with a strong equatorial easterly wind bias during boreal autumn accompanied by physically consistent biases in precipitation, sea surface temperature (SST), and subsurface ocean temperature. The analyses show that such IOD-like biases can be traced back to errors in the South Asian summer monsoon. A southwest summer monsoon that is too weak over the Arabian Sea generates a warm SST bias over the western equatorial IO. In boreal autumn, Bjerknes feedback helps amplify the error into an IOD-like bias pattern in wind, precipitation, SST, and subsurface ocean temperature. Such mean state biases result in an interannual IOD variability that is too strong. Most models project an IOD-like future change for the boreal autumn mean state in the global warming scenario, which would result in more frequent occurrences of extreme positive IOD events in the future with important consequences to Indonesia and East Africa. The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) characterizes this future IOD-like projection in the mean state as robust based on consistency among models, but the authors’ results cast doubts on this conclusion since models with larger IOD amplitude biases tend to produce stronger IOD-like projected changes in the future.”
Li, G., S. Xie, and Y. Du, 2015: Monsoon-Induced Biases of Climate Models over the Tropical Indian Ocean. J. Climate, 28, 3058–3072, https://doi.org/10.1175/JCLI-D-14-00740.1. [FULL TEXT]

Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming – Cai et al. (2014)
“The Indian Ocean dipole is a prominent mode of coupled ocean–atmosphere variability, affecting the lives of millions of people in Indian Ocean rim countries. In its positive phase, sea surface temperatures are lower than normal off the Sumatra–Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) events of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries but devastating droughts in eastern Indian Ocean rim countries. Despite these serious consequences, the response of pIOD events to greenhouse warming is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD events will increase by almost a factor of three, from one event every 17.3 years over the twentieth century to one event every 6.3 years over the twenty-first century. We find that a mean state change—with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean—facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD events, suggesting an increasing frequency of extreme climate and weather events in regions affected by the pIOD.”
Wenju Cai, Agus Santoso, Guojian Wang, Evan Weller, Lixin Wu, Karumuri Ashok, Yukio Masumoto & Toshio Yamagata (2014). Nature volume 510:254–258. doi:10.1038/nature13327. [FULL TEXT]

Projected response of the Indian Ocean Dipole to greenhouse warming – Cai et al. (2013)
“Natural modes of variability centred in the tropics, such as the El Niño/Southern Oscillation and the Indian Ocean Dipole, are a significant source of interannual climate variability across the globe. Future climate warming could alter these modes of variability. For example, with the warming projected for the end of the twenty-first century, the mean climate of the tropical Indian Ocean is expected to change considerably. These changes have the potential to affect the Indian Ocean Dipole, currently characterized by an alternation of anomalous cooling in the eastern tropical Indian Ocean and warming in the west in a positive dipole event, and the reverse pattern for negative events. The amplitude of positive events is generally greater than that of negative events. Mean climate warming in austral spring is expected to lead to stronger easterly winds just south of the Equator, faster warming of sea surface temperatures in the western Indian Ocean compared with the eastern basin, and a shoaling equatorial thermocline. The mean climate conditions that result from these changes more closely resemble a positive dipole state. However, defined relative to the mean state at any given time, the overall frequency of events is not projected to change — but we expect a reduction in the difference in amplitude between positive and negative dipole events.”
Cai, W., Zheng, X., Weller, E. et al. Projected response of the Indian Ocean Dipole to greenhouse warming. Nature Geosci 6, 999–1007 (2013) doi:10.1038/ngeo2009. [FULL TEXT]

Indian Ocean Dipole Response to Global Warming in the CMIP5 Multimodel Ensemble – Zheng et al. (2013)
“The response of the Indian Ocean dipole (IOD) mode to global warming is investigated based on simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). In response to increased greenhouse gases, an IOD-like warming pattern appears in the equatorial Indian Ocean, with reduced (enhanced) warming in the east (west), an easterly wind trend, and thermocline shoaling in the east. Despite a shoaling thermocline and strengthened thermocline feedback in the eastern equatorial Indian Ocean, the interannual variance of the IOD mode remains largely unchanged in sea surface temperature (SST) as atmospheric feedback and zonal wind variance weaken under global warming. The negative skewness in eastern Indian Ocean SST is reduced as a result of the shoaling thermocline. The change in interannual IOD variance exhibits some variability among models, and this intermodel variability is correlated with the change in thermocline feedback. The results herein illustrate that mean state changes modulate interannual modes, and suggest that recent changes in the IOD mode are likely due to natural variations.”
Zheng, X., S. Xie, Y. Du, L. Liu, G. Huang, and Q. Liu, 2013: Indian Ocean Dipole Response to Global Warming in the CMIP5 Multimodel Ensemble. J. Climate, 26, 6067–6080, https://doi.org/10.1175/JCLI-D-12-00638.1. [FULL TEXT]

Indian Ocean Dipole Response to Global Warming: Analysis of Ocean–Atmospheric Feedbacks in a Coupled Model – Zheng et al. (2010)
“Low-frequency modulation and change under global warming of the Indian Ocean dipole (IOD) mode are investigated with a pair of multicentury integrations of a coupled ocean–atmosphere general circulation model: one under constant climate forcing and one forced by increasing greenhouse gas concentrations. In the unforced simulation, there is significant decadal and multidecadal modulation of the IOD variance. The mean thermocline depth in the eastern equatorial Indian Ocean (EEIO) is important for the slow modulation, skewness, and ENSO correlation of the IOD. With a shoaling (deepening) of the EEIO thermocline, the thermocline feedback strengthens, and this leads to an increase in IOD variance, a reduction of the negative skewness of the IOD, and a weakening of the IOD–ENSO correlation. In response to increasing greenhouse gases, a weakening of the Walker circulation leads to easterly wind anomalies in the equatorial Indian Ocean; the oceanic response to weakened circulation is a thermocline shoaling in the EEIO. Under greenhouse forcing, the thermocline feedback intensifies, but surprisingly IOD variance does not. The zonal wind anomalies associated with IOD are found to weaken, likely due to increased static stability of the troposphere from global warming. Linear model experiments confirm this stability effect to reduce circulation response to a sea surface temperature dipole. The opposing changes in thermocline and atmospheric feedbacks result in little change in IOD variance, but the shoaling thermocline weakens IOD skewness. Little change under global warming in IOD variance in the model suggests that the apparent intensification of IOD activity during recent decades is likely part of natural, chaotic modulation of the ocean–atmosphere system or the response to nongreenhouse gas radiative changes.”
Zheng, X., S. Xie, G.A. Vecchi, Q. Liu, and J. Hafner, 2010: Indian Ocean Dipole Response to Global Warming: Analysis of Ocean–Atmospheric Feedbacks in a Coupled Model. J. Climate, 23, 1240–1253, https://doi.org/10.1175/2009JCLI3326.1. [FULL TEXT]

Recent unprecedented skewness towards positive Indian Ocean Dipole occurrences and its impact on Australian rainfall – Cai et al. (2009)
“Is the recent high frequency of positive Indian Ocean Dipole (pIOD) events a consequence of global warming? Using available observations and reanalyses, we show that the pIOD occurrences increase from about four per 30 years early in the 20th century to about 10 over the last 30 years; by contrast, the number of negative Indian Ocean Dipole (nIOD) events decreases from about 10 to two over the same periods, respectively. A skewness measure, defined as the difference in occurrences of pIODs and nIODs, illustrates a systematic trend in this parameter commencing early in the 20th century. After 1950, there are more pIODs than nIODs, with consistent mean circulation changes in the pIOD‐prevalent seasons. Over southeastern Australia (SEA), these changes potentially account for much of the observed austral winter and spring rainfall reduction since 1950. These features are consistent with projected future climate change and hence with what is expected from global warming.”
Cai, W., Cowan, T., and Sullivan, A. ( 2009), Recent unprecedented skewness towards positive Indian Ocean Dipole occurrences and its impact on Australian rainfall, Geophys. Res. Lett., 36, L11705, doi:10.1029/2009GL037604. [FULL TEXT]

Climate change contributes to more frequent consecutive positive Indian Ocean Dipole events – Cai et al. (2009)
“Are the 2006–2008 three‐consecutive positive Indian Ocean Dipole (pIOD) events linked to climate change? Using 20th century experiments submitted for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), we show that a 19‐model average IOD index over the 1950–1999 period yields an upward trend. The associated circulation trends provide a favourable environment for pIOD development, leading to a 17% increase in pIOD frequency compared with the case in which trends are removed. The majority of the increase manifests as a frequency increase in the two‐ and three‐consecutive events. The circulation trends are in turn consistent with wind changes associated with a weaker Walker circulation in the Pacific and an enhanced land‐sea temperature contrast in the Indian Ocean (IO) sector. Our results suggest that although it is difficult to attribute the trigger of the recent consecutive pIODs, climate change is increasing the occurrences of such events.”
Cai, W., Sullivan, A., and Cowan, T. ( 2009), Climate change contributes to more frequent consecutive positive Indian Ocean Dipole events, Geophys. Res. Lett., 36, L23704, doi:10.1029/2009GL040163. [FULL TEXT]

Recent intensification of tropical climate variability in the Indian Ocean – Abram et al. (2008)
“The interplay of the El Niño Southern Oscillation, Asian monsoon and Indian Ocean Dipole (IOD) drives climatic extremes in and around the Indian Ocean. Historical and proxy records reveal changes in the behaviour of the El Niño Southern Oscillation and the Asian monsoon over recent decades. However, reliable instrumental records of the IOD cover only the past 50 years, and there is no consensus on long-term variability of the IOD or its possible response to greenhouse gas forcing. Here we use a suite of coral oxygen-isotope records to reconstruct a basin-wide index of IOD behaviour since AD 1846. Our record reveals an increase in the frequency and strength of IOD events during the twentieth century, which is associated with enhanced seasonal upwelling in the eastern Indian Ocean. Although the El Niño Southern Oscillation has historically influenced the variability of both the IOD and the Asian monsoon, we find that the recent intensification of the IOD coincides with the development of direct, positive IOD–monsoon feedbacks. We suggest that projected greenhouse warming may lead to a redistribution of rainfall across the Indian Ocean and a growing interdependence between the IOD and Asian monsoon precipitation variability.”
Abram, N., Gagan, M., Cole, J. et al. Recent intensification of tropical climate variability in the Indian Ocean. Nature Geosci 1, 849–853 (2008) doi:10.1038/ngeo357. [FULL TEXT]

GCM simulations of the Indian Ocean dipole influence on East African rainfall: Present and future – Conway et al. (2007)
“Six coupled GCMs are assessed in terms of their ability to simulate observed characteristics of East African rainfall, the Indian Ocean dipole and their temporal correlation. Model results are then used to analyze the future behaviour of rainfall and the DMI. All models simulate reasonably well the spatial distribution and variability of annual and seasonal rainfall over the 1961–1990 period. Model simulation of observed DMI characteristics is less consistent with observations, however, five models reproduce similar correlations to those observed between the DMI and East African short rains (SON). In the future, there are no clear inter‐model patterns of rainfall or DMI behaviour. In this sample of models four (two) out of six simulate modest increases (decreases) in annual rainfall by the 2080s. For SON, three of the six models indicate a trend towards increasingly positive phase of the DMI, two indicate a decrease and one shows no substantial change.”
Conway, D., Hanson, C. E., Doherty, R., and Persechino, A. ( 2007), GCM simulations of the Indian Ocean dipole influence on East African rainfall: Present and future, Geophys. Res. Lett., 34, L03705, doi:10.1029/2006GL027597. [FULL TEXT]

Papers on Australia wildfires and climate change

This is a list of papers on Australia wildfires and climate change. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

UPDATE (January 10, 2020): Cai et al. (2009) added.

Climate change effects on the frequency, seasonality and interannual variability of suitable prescribed burning weather conditions in south-eastern Australia – Clarke et al. (2019)
“Despite the importance of prescribed burning in contemporary fire management, there is little understanding of how climate change will influence the weather conditions under which it is deployed. We provide quantitative estimates of potential changes in the number of prescribed burning days in coastal NSW in south-eastern Australia, a fire-prone area dominated by dry sclerophyll forests. Burning days are calculated from an objectively designed regional climate model ensemble using three definitions of suitable weather conditions based on: a literature search (Literature), actual weather observed during recorded prescribed burns (Observed) and operational guidelines (Operational). Contrary to some claims, evidence for a decrease in prescribed burning days under projected future climates is weak. We found a complex pattern of changes, with the potential for substantial and widespread increases in the current burning seasons of autumn (March-May) and spring (August-October). Projected changes were particularly uncertain in northern NSW, spanning substantial increases and decreases during autumn. The magnitude of projected changes in the frequency of burning days was highly sensitive to which definition of suitable weather conditions was used, with a relatively small change for the Operational definition (+0.3 to +1.9 days per year across the study area) and larger ranges for the Observed (+0.2 to +7.9 days) and Literature (+1.7 to +6.2 days) definitions. Interannual variability in the number of burning days is projected to increase slightly under projected climate change. Our study highlights the need for a better understanding of the weather conditions required for safe and effective prescribed burning. Our analysis provides practitioners with quantitative information to assess their exposure to a range of potential changes in the frequency, seasonality and variability of prescribed burning weather conditions.”
Hamish Clarke, Bruce Tran, Matthias M. Boer, Owen Price, Belinda Kenny, Ross Bradstock (2019). Agricultural and Forest Meteorology 271(15):148-157. doi:https://doi.org/10.1016/j.agrformet.2019.03.005.

Future changes in extreme weather and pyroconvection risk factors for Australian wildfires – Dowdy et al. (2019)
“Extreme wildfires have recently caused disastrous impacts in Australia and other regions of the world, including events with strong convective processes in their plumes (i.e., strong pyroconvection). Dangerous wildfire events such as these could potentially be influenced by anthropogenic climate change, however, there are large knowledge gaps on how these events might change in the future. The McArthur Forest Fire Danger Index (FFDI) is used to represent near-surface weather conditions and the Continuous Haines index (CH) is used here to represent lower to mid-tropospheric vertical atmospheric stability and humidity measures relevant to dangerous wildfires and pyroconvective processes. Projected changes in extreme measures of CH and FFDI are examined using a multi-method approach, including an ensemble of global climate models together with two ensembles of regional climate models. The projections show a clear trend towards more dangerous near-surface fire weather conditions for Australia based on the FFDI, as well as increased pyroconvection risk factors for some regions of southern Australia based on the CH. These results have implications for fields such as disaster risk reduction, climate adaptation, ecology, policy and planning, noting that improved knowledge on how climate change can influence extreme wildfires can help reduce future impacts of these events.”
Andrew J. Dowdy, Hua Ye, Acacia Pepler, Marcus Thatcher, Stacey L. Osbrough, Jason P. Evans, Giovanni Di Virgilio & Nicholas McCarthy (2019). Scientific Reports 9:10073. doi:10.1038/s41598-019-46362-x. [FULL TEXT]

Exploring the future change space for fire weather in southeast Australia – Clarke & Evans (2019)
“High-resolution projections of climate change impacts on fire weather conditions in southeast Australia out to 2080 are presented. Fire weather is represented by the McArthur Forest Fire Danger Index (FFDI), calculated from an objectively designed regional climate model ensemble. Changes in annual cumulative FFDI vary widely, from − 337 (− 21%) to + 657 (+ 24%) in coastal areas and − 237 (− 12%) to + 1143 (+ 26%) in inland areas. A similar spread is projected in extreme FFDI values. In coastal regions, the number of prescribed burning days is projected to change from − 11 to + 10 in autumn and − 10 to + 3 in spring. Across the ensemble, the most significant increases in fire weather and decreases in prescribed burn windows are projected to take place in spring. Partial bias correction of FFDI leads to similar projections but with a greater spread, particularly in extreme values. The partially bias-corrected FFDI performs similarly to uncorrected FFDI compared to the observed annual cumulative FFDI (ensemble root mean square error spans 540 to 1583 for uncorrected output and 695 to 1398 for corrected) but is generally worse for FFDI values above 50. This emphasizes the need to consider inter-variable relationships when bias-correcting for complex phenomena such as fire weather. There is considerable uncertainty in the future trajectory of fire weather in southeast Australia, including the potential for less prescribed burning days and substantially greater fire danger in spring. Selecting climate models on the basis of multiple criteria can lead to more informative projections and allow an explicit exploration of uncertainty.”
Clarke, H. & Evans, J.P. Theor Appl Climatol (2019) 136: 513. https://doi.org/10.1007/s00704-018-2507-4. [FULL TEXT]

On Determining the Impact of Increasing Atmospheric CO2 on the Record Fire Weather in Eastern Australia in February 2017 – Hope et al. (2019)
“February 2017 saw a broad region with record fire weather across central-eastern Australia. A hybrid attribution technique using modified observations and a seasonal forecast framework did not give a clear signal as to the influence of increasing atmospheric CO2 on the fire weather.”
Pandora Hope, Mitchell T. Black, Eun-Pa Lim, Andrew Dowdy, Guomin Wang, Acacia S. Pepler, and Robert J. B. Fawcett (2019). Bulletin of the American Meteorological Society, vol. 100, issue 1, pp. S111-S117. doi:10.1175/BAMS-D-18-0135.1. [FULL TEXT]

Climatological Variability of Fire Weather in Australia – Dowdy (2018)
“Long-term variations in fire weather conditions are examined throughout Australia from gridded daily data from 1950 to 2016. The McArthur forest fire danger index is used to represent fire weather conditions throughout this 67-yr period, calculated on the basis of a gridded analysis of observations over this time period. This is a complementary approach to previous studies (e.g., those based primarily on model output, reanalysis, or individual station locations), providing a spatially continuous and long-term observations-based dataset to expand on previous research and produce climatological guidance information for planning agencies. Long-term changes in fire weather conditions are apparent in many regions. In particular, there is a clear trend toward more dangerous conditions during spring and summer in southern Australia, including increased frequency and magnitude of extremes, as well as indicating an earlier start to the fire season. Changes in fire weather conditions are attributable at least in part to anthropogenic climate change, including in relation to increasing temperatures. The influence of El Niño–Southern Oscillation (ENSO) on fire weather conditions is found to be broadly consistent with previous studies (indicating more severe fire weather in general for El Niño conditions than for La Niña conditions), but it is demonstrated that this relationship is highly variable (depending on season and region) and that there is considerable potential in almost all regions of Australia for long-range prediction of fire weather (e.g., multiweek and seasonal forecasting). It is intended that improved understanding of the climatological variability of fire weather conditions will help lead to better preparedness for risks associated with dangerous wildfires in Australia.”
Dowdy, A.J., 2018: Climatological Variability of Fire Weather in Australia. J. Appl. Meteor. Climatol., 57, 221–234, https://doi.org/10.1175/JAMC-D-17-0167.1. [FULL TEXT]

Pyroconvection Risk in Australia: Climatological Changes in Atmospheric Stability and Surface Fire Weather Conditions – Dowdy & Pepler (2018)
“Extreme wildfires with strong convective processes in their plumes have recently led to disastrous impacts on various regions of the world. The Continuous Haines index (CH) is used in Australia to represent vertical atmospheric stability and humidity measures relating to pyroconvective processes. CH climatology is examined here using reanalysis data from 1979 to 2016, revealing large spatial and seasonal variations throughout Australia. Various measures of severity are investigated, including regionally specific thresholds. CH is combined with near‐surface fire weather conditions, as a type of compound event, and is examined in relation to environmental conditions associated with pyroconvection. Significant long‐term changes in CH are found for some regions and seasons, with these changes corresponding to changes in near‐surface conditions in some cases. In particular, an increased risk of pyroconvection is identified for southeast Australia during spring and summer, due to decreased vertical atmospheric stability and humidity combined with more severe near‐surface conditions.”
Dowdy, A. J., & Pepler, A. ( 2018). Pyroconvection risk in Australia: Climatological changes in atmospheric stability and surface fire weather conditions. Geophysical Research Letters, 45, 2005– 2013. https://doi.org/10.1002/2017GL076654. [FULL TEXT]

Fire frequency analysis for different climatic stations in Victoria, Australia – Khastagir (2018)
“Frequent occurrence of fire events will have severe impact on Victoria’s water supply catchments. Hence, it is important to perform fire frequency analysis to obtain fire frequency curves (FFC) on fire intensity using Forest Fire Danger Index (FFDI) at different parts of Victoria. FFDI is a measure of fire initiation, spreading speed and containment difficulty. FFC will guide water harvesting by providing information with regard to future fire events and the subsequent impact on catchment yield. Five probability distributions, namely normal, Log Pearson Type III (LPIII), gamma, log-normal and Weibull distributions were used for the development of FFCs at ten selected meteorological stations spread all over Victoria. LPIII distribution was identified as the best fit distribution for Victoria and subsequently applied for an additional 30 more stations to show spatial variability for the entire Victoria.”
Anirban Khastagir (2018). Natural Hazards volume 93, pages 787–802. doi:https://doi.org/10.1007/s11069-018-3324-x.

Fanning the Blame: Media Accountability, Climate and Crisis on the Australian “Fire Continent” – Anderson et al. (2018)
“This paper raises questions of media coverage of “compounded crises” related to extreme weather disaster, in the context of urgent calls to address the implications of a changing climate. Through media analysis, it examines the ways debate over bushfire protection policy was framed and made culturally meaningful, thereby politically consequential, in the wake of the worst bushfires in modern Australian history, Black Saturday (2009). The fires, in which 173 people died, led to a Royal Commission and fierce debate over the use of prescribed burning to reduce bushfire hazard. Longitudinal analysis of local, state and national mainstream media coverage (2009–2016) reveals blame games that targeted environmentalists and the government, which near-silenced meaningful discussion of the complexity of fire science, impacts of climate change on weather conditions, and calls for adaptation. By exploring the media’s constitutive role in crisis response, the paper highlights the legacy and potency of ideological conflict that shapes the media-policy nexus in Australia.”
Deb Anderson, Philip Chubb & Monika Djerf-Pierre (2018) Fanning the Blame: Media Accountability, Climate and Crisis on the Australian “Fire Continent”, Environmental Communication, 12:7, 928-941, DOI: 10.1080/17524032.2018.1424008. [FULL TEXT]

Big data integration shows Australian bush-fire frequency is increasing significantly – Dutta et al. (2016)
“Increasing Australian bush-fire frequencies over the last decade has indicated a major climatic change in coming future. Understanding such climatic change for Australian bush-fire is limited and there is an urgent need of scientific research, which is capable enough to contribute to Australian society. Frequency of bush-fire carries information on spatial, temporal and climatic aspects of bush-fire events and provides contextual information to model various climate data for accurately predicting future bush-fire hot spots. In this study, we develop an ensemble method based on a two-layered machine learning model to establish relationship between fire incidence and climatic data. In a 336 week data trial, we demonstrate that the model provides highly accurate bush-fire incidence hot-spot estimation (91% global accuracy) from the weekly climatic surfaces. Our analysis also indicates that Australian weekly bush-fire frequencies increased by 40% over the last 5 years, particularly during summer months, implicating a serious climatic shift.”
Ritaban Dutta, Aruneema Das and Jagannath Aryal (2016). Royal Society Open Science 3(2). doi:https://doi.org/10.1098/rsos.150241. [FULL TEXT]

Natural hazards in Australia: extreme bushfire – Sharples et al. (2016)
“Bushfires are one of the most frequent natural hazards experienced in Australia. Fires play an important role in shaping the landscape and its ecological dynamics, but may also have devastating effects that cause human injuries and fatalities, as well as broad-scale environmental damage. While there has been considerable effort to quantify changes in the occurrence of bushfire in Australia, a comprehensive assessment of the most extreme bushfire cases, which exact the greatest economic and environmental impacts, is lacking. In this paper we reflect upon recently developed understanding of bushfire dynamics to consider (i) historical changes in the occurrence of extreme bushfires, and (ii) the potential for increasing frequency in the future under climate change projections. The science of extreme bushfires is still a developing area, thus our conclusions about emerging patterns in their occurrence should be considered tentative. Nonetheless, historical information on noteworthy bushfire events suggests an increased occurrence in recent decades. Based on our best current understanding of how extreme bushfires develop, there is strong potential for them to increase in frequency in the future. As such there is a pressing need for a greater understanding of these powerful and often destructive phenomena.”
Sharples, J.J., Cary, G.J., Fox-Hughes, P. et al. Climatic Change (2016) 139: 85. https://doi.org/10.1007/s10584-016-1811-1. [FULL TEXT]

ENSO controls interannual fire activity in southeast Australia – Mariani et al. (2016)
“El Niño–Southern Oscillation (ENSO) is the main mode controlling the variability in the ocean‐atmosphere system in the South Pacific. While the ENSO influence on rainfall regimes in the South Pacific is well documented, its role in driving spatiotemporal trends in fire activity in this region has not been rigorously investigated. This is particularly the case for the highly flammable and densely populated southeast Australian sector, where ENSO is a major control over climatic variability. Here we conduct the first region‐wide analysis of how ENSO controls fire activity in southeast Australia. We identify a significant relationship between ENSO and both fire frequency and area burnt. Critically, wavelet analyses reveal that despite substantial temporal variability in the ENSO system, ENSO exerts a persistent and significant influence on southeast Australian fire activity. Our analysis has direct application for developing robust predictive capacity for the increasingly important efforts at fire management.”
Mariani, M., Fletcher, M.‐S., Holz, A., and Nyman, P. ( 2016), ENSO controls interannual fire activity in southeast Australia, Geophys. Res. Lett., 43, 10,891– 10,900, doi:10.1002/2016GL070572. [FULL TEXT]

People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands – Bird et al. (2016)
“While evidence mounts that indigenous burning has a significant role in shaping pyrodiversity, the processes explaining its variation across local and external biophysical systems remain limited. This is especially the case with studies of climate–fire interactions, which only recognize an effect of humans on the fire regime when they act independently of climate. In this paper, we test the hypothesis that an anthropogenic fire regime (fire incidence, size and extent) does not covary with climate. In the lightning regime, positive El Niño southern oscillation (ENSO) values increase lightning fire incidence, whereas La Niña (and associated increases in prior rainfall) increase fire size. ENSO has the opposite effect in the Martu regime, decreasing ignitions in El Niño conditions without affecting fire size. Anthropogenic ignition rates covary positively with high antecedent rainfall, whereas fire size varies only with high temperatures and unpredictable winds, which may reduce control over fire spread. However, total area burned is similarly predicted by antecedent rainfall in both regimes, but is driven by increases in fire size in the lightning regime, and fire number in the anthropogenic regime. We conclude that anthropogenic regimes covary with climatic variation, but detecting the human–climate–fire interaction requires multiple measures of both fire regime and climate.”
Bliege Bird Rebecca, Bird Douglas W. and Codding Brian F. People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands. Phil. Trans. R. Soc. B. 371(1696). doi:https://doi.org/10.1098/rstb.2015.0343. [FULL TEXT]

Responses of resilience traits to gradients of temperature, rainfall and fire frequency in fire-prone, Australian forests: potential consequences of climate change – Hammill et al. (2016)
“The composition of plant communities may be driven by responses of key plant resilience traits (resprouting R+, non-resprouting R−, persistent P+ and transient P− seedbanks) to either resource competition or disturbance regimes. We explored responses of overall species richness and the richness of herbs and shrubs within the three most common functional types (i.e. facultative resprouters R+P+, obligate resprouters R+P−, obligate seeders R−P+) to orthogonal combinations of temperature (MAT), rainfall (MAP) and fire frequency (FF) in Dry Sclerophyll Forest in the Sydney basin (south-eastern Australia). R+ and P+ species were predominant (>72 % of total species). Overall richness was a significant positive function of MAT, MAP and FF. Positive relationships between species richness and MAP, MAT and FF occurred across all trait and functional type groups, with MAP being the most influential and FF the least. Responses of proportions of species within trait- and functional-type groups were complex. Proportion of R+ species was negatively related to MAT and MAP, but species-rich herb and shrub R+P+ proportions were positively and negatively related to MAT, respectively. The herb R+P+ proportion was negatively related to FF. The results were inconsistent with the disturbance frequency and resource competition models of resilience variation. Rises in MAT under climate change have the potential not only to increase overall species plus richness across all trait groups but also to diminish shrubs relative to herbs in the key R+P+ functional types. Such a scenario is highly uncertain given the variability in future MAP projections for the region.”
Hammill, K., Penman, T. & Bradstock, R. Plant Ecol (2016) 217: 725. https://doi.org/10.1007/s11258-016-0578-9.

Divergent responses of fire to recent warming and drying across south‐eastern Australia – Bradstock et al. (2014)
“The response of fire to climate change may vary across fuel types characteristic of differing vegetation types (i.e. litter vs. grass). Models of fire under climatic change capture these differing potential responses to varying degrees. Across south‐eastern Australia, an elevation in the severity of weather conditions conducive to fire has been measured in recent decades. We examined trends in area burned (1975–2009) to determine if a corresponding increase in fire had occurred across the diverse range of ecosystems found in this part of the continent. We predicted that an increase in fire, due to climatic warming and drying, was more likely to have occurred in moist, temperate forests near the coast than in arid and semiarid woodlands of the interior, due to inherent contrasts in the respective dominant fuel types (woody litter vs. herbaceous fuels). Significant warming (i.e. increased temperature and number of hot days) and drying (i.e. negative precipitation anomaly, number of days with low humidity) occurred across most of the 32 Bioregions examined. The results were mostly consistent with predictions, with an increase in area burned in seven of eight forest Bioregions, whereas area burned either declined (two) or did not change significantly (nine) in drier woodland Bioregions. In 12 woodland Bioregions, data were insufficient for analysis of temporal trends in fire. Increases in fire attributable mostly to warming or drying were confined to three Bioregions. In the remainder, such increases were mostly unrelated to warming or drying trends and therefore may be due to other climate effects not explored (e.g. lightning ignitions) or possible anthropogenic influences. Projections of future fire must therefore not only account for responses of different fuel systems to climatic change but also the wider range of ecological and human effects on interactions between fire and vegetation.”
Bradstock, R., Penman, T., Boer, M., Price, O. and Clarke, H. (2014), Divergent responses of fire to recent warming and drying across south‐eastern Australia. Glob Change Biol, 20: 1412-1428. doi:10.1111/gcb.12449.

Changes in Australian fire weather between 1973 and 2010 – Clarke et al. (2013)
“A data set of observed fire weather in Australia from 1973–2010 is analysed for trends using the McArthur Forest Fire Danger Index (FFDI). Annual cumulative FFDI, which integrates daily fire weather across the year, increased significantly at 16 of 38 stations. Annual 90th percentile FFDI increased significantly at 24 stations over the same period. None of the stations examined recorded a significant decrease in FFDI. There is an overall bias in the number of significant increases towards the southeast of the continent, while the largest trends occur in the interior of the continent and the smallest occur near the coast. The largest increases in seasonal FFDI occurred during spring and autumn, although with different spatial patterns, while summer recorded the fewest significant trends. These trends suggest increased fire weather conditions at many locations across Australia, due to both increased magnitude of FFDI and a lengthened fire season. Although these trends are consistent with projected impacts of climate change on FFDI, this study cannot separate the influence of climate change, if any, with that of natural variability.”
Clarke, H., Lucas, C. and Smith, P. (2013), Changes in Australian fire weather between 1973 and 2010. Int. J. Climatol., 33: 931-944. doi:10.1002/joc.3480. [FULL TEXT]

Fire and carbon dynamics under climate change in south-eastern Australia: insights from FullCAM and FIRESCAPE modelling – King et al. (2011)
“This study used simulation modelling to investigate fire and carbon dynamics for projected warmer and drier climates in the south-eastern Australian high country. A carbon accounting model FullCAM and the landscape fire regime simulator FIRESCAPE were combined and used to simulate several fire management options under three climate scenarios – the recent climate (1975–2005); a moderate climate projected for 2070 (B1); and a more extreme climate projected for 2070 (A1FI). For warmer and drier climates, model simulations predicted (i) an increase in fire incidence; (ii) larger areas burned; (iii) higher mean fire intensities; (iv) shorter fire cycle lengths; (v) a greater proportion of fires burning earlier in the fire season; (vi) a reduction in carbon stores; (vii) a reduction in carbon sequestration rates; and (viii) an increase in the proportion of stored carbon emitted to the atmosphere. Prescribed burning at historical or twice historical levels had no effect on fire or carbon dynamics. In contrast, increasing the initial attack success (a surrogate for suppression) partially offset the adverse effects of warmer and drier climates on fire activity, but not on carbon dynamics. For the south-eastern Australian high country, simulations indicated that fire and carbon dynamics are sensitive to climate change, with simulated fire management only being able to partially offset the adverse effects of warmer and drier climate.”
King Karen J., de Ligt Robert M., Cary Geoffrey J. (2011) Fire and carbon dynamics under climate change in south-eastern Australia: insights from FullCAM and FIRESCAPE modelling. International Journal of Wildland Fire 20, 563-577. doi:https://doi.org/10.1071/WF09073.

Assessing the impact of climate change on extreme fire weather events over southeastern Australia – Hasson et al. (2009)
“Extreme fire weather events in southeastern Australia are frequently associated with strong cold fronts moving through the area. A recent study has shown that the 850 hPa temperature and the magnitude of its gradient over a small region of southeastern Australia provide a simple means of discriminating the most extreme cold frontal events during the last 40 yr from reanalysis data sets. Applying this technique to 10 general circulation models (GCMs) from the Coupled Model Intercomparison Project and calibrating the temperature gradient and temperature climatology of each model’s simulation of the climate of the 20th century against the reanalysis climates allows estimates of likely changes in frequency of this type of extreme cold front in the middle and end of the 21st century. Applying this analysis to the output of 10 GCM simulations of the 21st century, using low and high greenhouse gas emissions scenarios, suggests that the frequency of such events will increase from around 1 event every 2 yr during the late 20th century to around 1 event per year in the middle of the 21st century and 1 to 2 events per year by the end of the 21st century; however, there is a great degree of variation between models. In addition to a greater overall increase under the high emissions scenario, the rate at which the increase occurs amplifies during the second half of the century, whereas under the low emissions scenario the number of extreme cases stabilizes, although still at a higher rate than that experienced in the late 20th century.”
Hasson AEA, Mills GA, Timbal B, Walsh K (2009) Assessing the impact of climate change on extreme fire weather events over southeastern Australia. Clim Res 39:159-172. https://doi.org/10.3354/cr00817. [FULL TEXT]

Positive Indian Ocean Dipole events precondition southeast Australia bushfires – Cai et al. (2009)
“The devastating “Black Saturday” bushfire inferno in the southeast Australian state of Victoria in early February 2009 and the “Ash Wednesday” bushfires in February 1983 were both preceded by a positive Indian Ocean Dipole (pIOD) event. Is there a systematic pIOD linkage beyond these two natural disasters? We show that out of 21 significant bushfires seasons since 1950, 11 were preceded by a pIOD. During Victoria’s wet season, particularly spring, a pIOD contributes to lower rainfall and higher temperatures exacerbating the dry conditions and increasing the fuel load leading into summer. Consequently, pIODs are effective in preconditioning Victoria for bushfires, more so than El Niño events, as seen in the impact on soil moisture on interannual time scales and in multi‐decadal changes since the 1950s. Given that the recent increase in pIOD occurrences is consistent with what is expected from global warming, an increased bushfire risk in the future is likely across southeast Australia.”
Cai, W., Cowan, T., and Raupach, M. ( 2009), Positive Indian Ocean Dipole events precondition southeast Australia bushfires, Geophys. Res. Lett., 36, L19710, doi:10.1029/2009GL039902. [FULL TEXT]

The impact of climate change on the risk of forest and grassland fires in Australia – Pitman et al. (2007)
“We explore the impact of future climate change on the risk of forest and grassland fires over Australia in January using a high resolution regional climate model, driven at the boundaries by data from a transitory coupled climate model. Two future emission scenarios (relatively high and relatively low) are used for 2050 and 2100 and four realizations for each time period and each emission scenario are run. Results show a consistent increase in regional-scale fire risk over Australia driven principally by warming and reductions in relative humidity in all simulations, under all emission scenarios and at all time periods. We calculate the probability density function for the fire risk for a single point in New South Wales and show that the probability of extreme fire risk increases by around 25% compared to the present day in 2050 under both relatively low and relatively high emissions, and that this increases by a further 20% under the relatively low emission scenario by 2100. The increase in the probability of extreme fire risk increases dramatically under the high emission scenario by 2100. Our results are broadly in-line with earlier analyses despite our use of a significantly different methodology and we therefore conclude that the likelihood of a significant increase in fire risk over Australia resulting from climate change is very high. While there is already substantial investment in fire-related management in Australia, our results indicate that this investment is likely to have to increase to maintain the present fire-related losses in Australia.”
Pitman, A.J., Narisma, G.T. & McAneney, J. The impact of climate change on the risk of forest and grassland fires in Australia. Climatic Change 84, 383–401 (2007) doi:10.1007/s10584-007-9243-6. [FULL TEXT]

The Sensitivity of Australian Fire Danger to Climate Change – Williams et al. (2001)
“Global climate change, such as that due to the proposed enhanced greenhouse effect, is likely to have a significant effect on biosphere-atmosphere interactions, including bushfire regimes. This study quantifies the possible impact of climate change on fire regimes by estimating changes in fire weather and the McArthur Forest Fire Danger Index (FDI), an index that is used throughout Australia to estimate fire danger. The CSIRO 9-level general circulation model(CSIRO9 GCM)is used to simulate daily and seasonal fire danger for the present Australian climate and for a doubled-CO2 climate. The impact assessment includes validation of the GCMs daily control simulation and the derivation of ‘correction factors’ which improve the accuracy of the fire danger simulation. In summary, the general impact of doubled-CO2 is to increase fire danger at all sites by increasing the number of days of very high and extreme fire danger.Seasonal fire danger responds most to the large CO2-induced changes in maximum temperature.”
Williams, A.A.J., Karoly, D.J. & Tapper, N. Climatic Change (2001) 49: 171. https://doi.org/10.1023/A:1010706116176. [FULL TEXT]

Fire Regime Sensitivity to Global Climate Change: An Australian Perspective – Cary & Banks (2000)
“The Australian eucalypt forests are highly adapted to fire, and their component species possess well-developed response mechanisms that ensure post-fire recovery of these ecosystems. Fire regimes, which may alter forest floristics and structure, have changed since pre-European times because of management practices and may again change because of a changing climate. Two complimentary approaches are used to determine spatial and temporal patterns of fire regimes, a) dendrochronology to determine pre- and post-European fire histories for specific sites and b) fire-climate-landscape modelling to predict spatial patterns in fire regimes for topographically complex landscapes. This paper brings together these two approaches which have been applied independently to the same forest in the Southern Tablelands of New South Wales. The model predictions of spatial patterns in fire regimes under the present climate provide reasonable results when compared with observed site fire histories. Also, model results indicate that around half of the landscape is likely to experience a significant increase in fire frequency as a result of climate change. These findings, which have implications for fire-prone forest environments world-wide, are discussed in relation to the effects that anthropogenic ignition have had on the fire frequency in the study area over the last century.”
Cary G.J., Banks J.C.G. (2000) Fire Regime Sensitivity to Global Climate Change: An Australian Perspective. In: Innes J.L., Beniston M., Verstraete M.M. (eds) Biomass Burning and Its Inter-Relationships with the Climate System. Advances in Global Change Research, vol 3. Springer, Dordrecht.

Papers on the Climategate

This is a list of papers on the Climategate. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Rhetorical Strategies for Scientific Authority: A Boundary-Work Analysis of ‘Climategate’ (Ramírez-i-Ollé, 2015)
Abstract: “The term ‘Climategate’ refers to the episode in November 2009 when emails between climate scientists were stolen and published online. The content of this private correspondence prompted criticism from diverse commentators who cast doubts on the methods, claims, and members of the climate science community. In response, individual scientists and scientific institutions published statements responding to the allegations of scientific fraud. Gieryn’s concept of ‘boundary-work’ can be used to analyse the rhetoric of scientists in situations where their legitimacy is disputed. More specifically, boundary-work can be used to analyse the responses of scientists in terms of: how they represent the attributes of science, what types of boundary-work they undertake (e.g. expulsion, expansion, and protection), and the professional interests that come into play. A boundary-work analysis of the commentaries published in the aftermath of Climategate reveals that scientists characterised climate science as consensual, asocial, and open. Scientists depicted climate science as consensual with the purpose of expelling dissenters and protecting areas of climate science from criticism. Scientists also described knowledge about climate as being ideally produced apart from society so that they could preserve their autonomy and exclude individuals who are accused of being ‘politically biased’. Scientists characterised climate science as necessarily open as the means to justify both existing and additional public funding for science and to avoid external corrective interventions against scientific opacity. Scientists and their critics alike interpreted the stolen emails as embarrassing deviations from the alleged social demands of a consensual, objective, and accessible science.”
Citation: Meritxell Ramírez-i-Ollé (2015) Rhetorical Strategies for Scientific Authority: A Boundary-Work Analysis of ‘Climategate’, Science as Culture, 24:4, 384-411, DOI: 10.1080/09505431.2015.1041902.

Public interest in climate change over the past decade and the effects of the ‘climategate’ media event (Anderegg & Goldsmith, 2014) [FULL TEXT]
Abstract: “Despite overwhelming scientific consensus concerning anthropogenic climate change, many in the non-expert public perceive climate change as debated and contentious. There is concern that two recent high-profile media events—the hacking of the University of East Anglia emails and the Himalayan glacier melt rate presented in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change—may have altered public opinion of climate change. While survey data is valuable for tracking public perception and opinion over time, including in response to climate-related media events, emerging methods that facilitate rapid assessment of spatial and temporal patterns in public interest and opinion could be exceptionally valuable for understanding and responding to these events’ effects. We use a novel, freely-available dataset of worldwide web search term volumes to assess temporal patterns of interest in climate change over the past ten years, with a particular focus on looking at indicators of climate change skepticism around the high-profile media events. We find that both around the world and in the US, the public searches for the issue as ‘global warming,’ rather than ‘climate change,’ and that search volumes have been declining since a 2007 peak. We observe high, but transient spikes of search terms indicating skepticism around the two media events, but find no evidence of effects lasting more than a few months. Our results indicate that while such media events are visible in the short-term, they have little effect on salience of skeptical climate search terms on longer time-scales.”
Citation: William R L Anderegg and Gregory R Goldsmith 2014 Environ. Res. Lett. 9 054005, https://doi.org/10.1088/1748-9326/9/5/054005.

Boundaries, breaches, and bridges: The case of Climategate (Garud et al. 2014) [FULL TEXT]
Abstract: “We examine the incident known as “Climategate” in which emails and other documents relating to climate scientists and their work were illegitimately accessed and posted to the Internet. The contents of the files prompted questions about the credibility of climate science and the legitimacy of some of the climate scientists’ practices. Multiple investigations unfolded to repair the boundary that had been breached. While exonerating the scientists of wrongdoing and endorsing the legitimacy of the consensus opinion, the investigating committees suggested revisions to some scientific practices. Despite this boundary repair work, the credibility and legitimacy of the scientific enterprise were not fully restored in the eyes of several stakeholders. We explore why this is the case, identify boundary bridging approaches to address these issues, and highlight policy implications.”
Citation: Raghu Garud, Joel Gehman, Arvind Karunakaran (2014). Research Policy 43(1): 60-73, https://doi.org/10.1016/j.respol.2013.07.007.

Climategate, Public Opinion, and the Loss of Trust (Leiserowitz et al. 2013) [FULL TEXT]
Abstract: “Nationally representative surveys conducted in 2008 and 2010 found significant declines in Americans’ climate change beliefs, risk perceptions, and trust in scientists. Drawing upon the Social Amplification of Risk Framework, this analysis empirically examines the impact of “climategate”—an international scandal resulting from the unauthorized release of emails between climate scientists in England and United States. The results demonstrate that “climategate” had a significant effect on public beliefs in global warming and trust in scientists. The loss of trust in scientists, however, was primarily among individuals with a strongly individualistic worldview or politically conservative ideology. Nonetheless, Americans overall continued to trust scientists more than other sources of information about global warming. Several other explanations for the declines in public understanding are also explored, including the poor state of the economy, a new administration and Congress, diminishing media attention, and abnormal winter weather.”
Citation: Anthony A. Leiserowitz, Edward W. Maibach, Connie Roser-Renouf, Nicholas Smith, Erica Dawson (2013), American Behavioral Scientist, 57(6): 818-837. https://doi.org/10.1177/0002764212458272.

Climategate: A Case Study in the Intersection of Facticity and Conspiracy Theory (Bricker, 2013)
Abstract: “In 2009, the Climate Research Unit had over 1,000 private e-mails stolen and made publicly available. Quickly, several of the e-mails were widely reported in the media: supposedly providing proof of conspiracy among scientists supporting the Anthropogenic Climate Change hypothesis. Despite the inaccuracy of the accusations, the charge of conspiracy stuck. In this essay, I argue that a set of interrelated variables (existing anti-elitism, the consistency of the charge with existing ideology, the perceived accuracy of the narrative, and the poor rhetorical response by the accused) caused the Climategate conspiracy to resonate even after the charge was proven false. This essay adds to contemporary rhetorical theory about conspiracy theory by considering variables beyond paranoid style and accuracy of the charge.”
Citation: Brett Jacob Bricker (2013) Climategate: A Case Study in the Intersection of Facticity and Conspiracy Theory, Communication Studies, 64:2, 218-239, DOI: 10.1080/10510974.2012.749294.

Climate change and ‘climategate’ in online reader comments: a mixed methods study (Koteyko et al. 2013) [FULL TEXT]
Abstract: “Climate change has rarely been out of the public spotlight in the first decade of this century. The high‐profile international meetings and controversies such as ‘climategate’ have highlighted the fact that it is as much a political issue as it is a scientific one, while also drawing our attention to the role of social media in reflecting, promoting or resisting such politicisation. In this article, we propose a framework for analysing one type of social media venue that so far has received little attention from social scientists – online reader comments. Like media reporting on climate change, reader comments on this reporting contribute to the diverse, complex and contested discourses on climate change, and can reveal the meanings and discursive resources brought to the ongoing debate by laypeople rather than political elites. The proposed framework draws on research in computer‐mediated communication, corpus linguistics and discourse analysis and takes into account both the content of such ‘lay talk’ and its linguistic characteristics within the specific parameters of the web‐based context. Using word frequencies, qualitative study of co‐text and user ratings, we analyse a large volume of comments published on the UK tabloid newspaper website at two different points in time – before and after the East Anglia controversy. The results reveal how stereotypes of science and politics are appropriated in this type of discourse, how readers’ constructions of climate science have changed after ‘climategate’, and how climate‐sceptic arguments are adopted and contested in computer‐mediated peer‐to‐peer interaction.”
Citation: Koteyko, N. , Jaspal, R. and Nerlich, B. (2013), Climate change and ‘climategate’ in online reader comments. The Geographical Journal, 179: 74-86. doi:10.1111/j.1475-4959.2012.00479.x.

The legacy of climategate: revitalizing or undermining climate science and policy? (Grundmann, 2012) [FULL TEXT]
Abstract: “The release of emails from a server at the University of East Anglia’s Climate Research Unit (CRU) in November 2009 and the following climategate controversy have become a topic for interpretation in the social sciences. This article picks out some of the most visible social science comments on the affair for discussion. These comments are compared to an account of what can be seen as problematic practices by climate scientists. There is general agreement in these comments that climate science needs more openness and transparency. But when evaluating climategate a variety of responses is seen, ranging from the apologetic to the highly critical, even condemning the practices in question. It is argued that reluctance to critically examine the climategate affair, including suspect practices of scientists, has to do with the nature of the debate which is highly politicized. A call is made for more reflection on this case which should not be closed off because of political expediency.”
Citation: Grundmann, R. (2012), The legacy of climategate: revitalizing or undermining climate science and policy?. WIREs Clim Change, 3: 281-288. doi:10.1002/wcc.166.

The legacy of climategate: undermining or revitalizing climate science and policy? (Maibach et al. 2012) [FULL TEXT]
Abstract: “In mid‐November 2009, emails were removed without authorization from a University of East Anglia server and posted to the internet; within 24 h an international scandal was born—alleging fraud by leading climate scientists—which almost immediately became known as climategate. Multiple investigations concluded that no fraud or scientific misconduct had occurred. Despite the exonerations, however, the email controversy has had impacts, both negative and positive. On the negative side, a small minority of the American public and a somewhat larger minority of American TV news professionals—mostly political conservatives—indicated that the controversy made them more certain that climate change is not happening, and undermined their trust in climate scientists. Conservative organizations and politicians continue to cite the controversy in justifying their opposition to government action on climate change. On the positive side, the controversy impressed upon the climate science community the need for improved communication and public engagement efforts, and many individuals and organizations have begun to address these needs. It also reminded the climate science community of the importance of transparency, data availability, and strong quality assurance procedures, stimulating many organizations to review their data management practices. Although it is too soon to gauge the lasting legacy of the controversy, if the climate science community takes it as an opportunity to improve its already high standards of scientific conduct—as well as improve its less well‐developed approach to public engagement—the long‐term prognosis is good.”
Citation: Maibach, E. , Leiserowitz, A. , Cobb, S. , Shank, M. , Cobb, K. M. and Gulledge, J. (2012), The legacy of climategate: undermining or revitalizing climate science and policy?. WIREs Clim Change, 3: 289-295. doi:10.1002/wcc.168.

“Climategate” and The Scientific Ethos (Grundmann, 2012) [FULL TEXT]
Abstract: “In late 2009, e-mails from a server at the Climate Research Unit at the University of East Anglia were released that showed some climate scientists in an unfavorable light. Soon this scandal was known as “Climategate” and a highly charged debate started to rage on blogs and in the mass media. Much of the debate has been about the question whether anthropogenic global warming was undermined by the revelations. But ethical issues, too, became part and parcel of the debate. This article aims to contribute to this debate, assessing the e-mail affair in the light of two normative analyses of science, one proposed by Robert Merton (and developed further by some of his followers), the second by a recent suggestion to use the concept of honest brokering in science policy interactions. On the basis of these analyses, different aspects of malpractice will be discussed and possible solutions will be suggested.”
Citation: Reiner Grundmann (2012) Science, Technology, & Human Values, 38(1):67-93, https://doi.org/10.1177/0162243911432318.

Climategate, Public Opinion, and the Loss of Trust (Leiserowitz et al. 2012) [FULL TEXT]
Abstract: “Nationally representative surveys conducted in 2008 and 2010 found significant declines in Americans’ climate change beliefs, risk perceptions, and trust in scientists. Drawing upon the Social Amplification of Risk Framework, this analysis empirically examines the impact of “climategate”—an international scandal resulting from the unauthorized release of emails between climate scientists in England and United States. The results demonstrate that “climategate” had a significant effect on public beliefs in global warming and trust in scientists. The loss of trust in scientists, however, was primarily among individuals with a strongly individualistic worldview or politically conservative ideology. Nonetheless, Americans overall continued to trust scientists more than other sources of information about global warming. Several other explanations for the declines in public understanding are also explored, including the poor state of the economy, a new administration and Congress, diminishing media attention, and abnormal winter weather.”
Citation: Anthony A. Leiserowitz, Edward W. Maibach, Connie Roser-Renouf, Nicholas Smith, Erica Dawson (2012) American Behavioral Scientist, 57(6):818-837, https://doi.org/10.1177/0002764212458272.

Advocacy in the tail: Exploring the implications of ‘climategate’ for science journalism and public debate in the digital age (Holliman, 2011) [FULL TEXT]
Abstract: “This article explores the evolving practices of science journalism and public debate in the digital age. The vehicle for this study is the release of digitally stored email correspondence, data and documents from the Climatic Research Unit at the University of East Anglia in the UK in the weeks immediately prior to the United Nations Copenhagen Summit (COP-15) in December 2009. Described using the journalistic shorthand of ‘climategate’, and initially promoted through socio-technical networks of bloggers, this episode became a global news story and the subject of several formal reviews. ‘Climategate’ illustrates that media-literate critics of anthropogenic explanations of climate change used digital tools to support their cause, making visible selected, newsworthy aspects of scientific information and the practices of scientists. In conclusion, I argue that ‘climategate’ may have profound implications for the production and distribution of science news, and how climate science is represented and debated in the digitally mediated public sphere.”
Citation: Holliman, R. (2011). Advocacy in the tail: Exploring the implications of ‘climategate’ for science journalism and public debate in the digital age. Journalism, 12(7), 832–846. https://doi.org/10.1177/1464884911412707.

“Climategate” Undermined Belief in Global Warming Among Many American TV Meteorologists (Maibach et al. 2011) [FULL TEXT]
Abstract: “Television (TV) meteorologists are a potentially important source of informal climate change education in that most American adults watch local TV news and consider TV weather reporters to be a trusted source of global warming information. In January 2010, we used a Web-based survey of TV meteorologists nationwide to assess the impact of “Climategate”—the unauthorized release of, and news stories about, e-mails between climate scientists in the United States and the United Kingdom—on their beliefs about climate change; the response rate was 52%. Most respondents (77%) had followed the story; 42% of those who did indicated it made them more certain that global warming is not happening. Conservatives (57%) were more likely than moderates (43%) and liberals (15%) to endorse this view (χ2 = 49.89, p < 0.001), and those who believed global warming is not happening (74%), or who did not know (46%), were more likely to endorse the view than those who believed it is happening (25%; χ2 = 108.59, p < 0.001). Multivariate analysis showed that political ideology, belief in global warming, and gender each predicted a negative impact of the story, but certifications from professional associations did not. Furthermore, respondents who followed the story reported less trust in climate scientists (2.8 versus 3.2; p < 0.01), and in the IPCC (2.2 versus 2.7; p < 0.01), than those who had not. We conclude that, at least temporarily, Climategate has likely impeded efforts to encourage some weathercasters to embrace the role of climate change educator. These results also suggest that many TV weathercasters responded to Climategate more through the lens of political ideology than through the lens of meteorology."
Citation: Maibach, E., J. Witte, and K. Wilson, 2011: “Climategate” Undermined Belief in Global Warming Among Many American TV Meteorologists. Bull. Amer. Meteor. Soc., 92, 31–37, https://doi.org/10.1175/2010BAMS3094.1.

‘Climategate’: Paradoxical Metaphors and Political Paralysis (Nerlich, 2010) [FULL TEXT]
Abstract: “Climate scepticism in the sense of climate denialism or contrarianism is not a new phenomenon, but it has recently been very much in the media spotlight. When, in November 2009, emails by climate scientists were published on the internet without their authors’ consent, a debate began in which climate sceptic bloggers used an extended network of metaphors to contest (climate) science. This article follows the so-called ‘climategate’ debate on the web and shows how a paradoxical mixture of religious metaphors and demands for ‘better science’ allowed those disagreeing with the theory of anthropogenic climate change to undermine the authority of science and call for political inaction with regard to climate change.”
Citation: Brigitte Nerlich (2010) Environmental Values, 19(4):419-442, doi:10.3197/096327110X531543.

The Global Warming of Climate Science: Climategate and the Construction of Scientific Facts (Ryghaug & Skjølsvold, 2010) [FULL TEXT]
Abstract: “This article analyses 1,073 e‐mails that were hacked from the Climatic Research Unit at the University of East Anglia in November 2009. The incident was popularly dubbed ‘Climategate’, indicating that the e‐mails reveal a scientific scandal. Here we analyse them differently. Rather than objecting to the exchanges based on some idea about proper scientific conduct, we see them as a rare glimpse into a situation where scientists collectively prepare for participation in heated controversy, with much focus on methodology. This allows us to study how scientists communicate informally about framing propositions of facts in the best possible way. Through the eyes of science and technology studies, the e‐mails provide an opportunity to study communication as part of science in the making across disciplines and laboratories. Analysed as ‘written conversation’ the e‐mails provide information about processes of consensus formation through ‘agonistic evaluations’ of other scientists’ work and persuasion of others to support one’s own work. Also, the e‐mails contain judgements about other groups and individual scientists. Consensus‐forming appeared as a precarious activity. Controversies could be quite resilient in the course of this decade‐long exchange, probably reflecting the complexity of the methodological challenges involved.”
Citation: Marianne Ryghaug & Tomas Moe Skjølsvold (2010) The Global Warming of Climate Science: Climategate and the Construction of Scientific Facts, International Studies in the Philosophy of Science, 24:3, 287-307, DOI: 10.1080/02698595.2010.522411.

Papers of Wally Broecker

A list of climate related papers where Wally Broecker (1931-2019) is the first author:

1957

Lamont Natural Radiocarbon Measurements IV https://www.jstor.org/stable/1752751

1958

The relation of deep sea sedimentation rates to variations in climate http://www.ajsonline.org/content/256/7/503.extract

Radiocarbon chronology of Lake Lahontan and Lake Bonneville https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/69/8/1009/5015

1959

Re-evaluation of the salt chronology of several Great Basin Lakes https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/70/5/601/5108

Lamont Radiocarbon Measurements VI https://www.cambridge.org/core/journals/radiocarbon/article/lamont-radiocarbon-measurements-vi/EE4DAF2397F34D5D7C1AEEE88CE750C1

1960

Evidence for an abrupt change in climate close to 11,000 years ago http://www.ajsonline.org/content/258/6/429.short

Natural radiocarbon in the Atlantic Ocean https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JZ065i009p02903

1965

Uranium-Series Dating of Corals and Oolites from Bahaman and Florida Key Limestones http://science.sciencemag.org/content/149/3679/58

Radiocarbon Chronology of Lake Lahontan and Lake Bonneville II, Great Basin https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/76/5/537/5914

1968

Milankovitch Hypothesis Supported by Precise Dating of Coral Reefs and Deep-Sea Sediments http://science.sciencemag.org/content/159/3812/297

In Defense of the Astronomical Theory of Glaciation https://link.springer.com/chapter/10.1007/978-1-935704-38-6_14

1970

Insolation changes, ice volumes, and the O18 record in deep‐sea cores https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/RG008i001p00169

1975

Climatic Change: Are We on the Brink of a Pronounced Global Warming? http://science.sciencemag.org/content/189/4201/460

1980

Modeling the Carbon System https://www.cambridge.org/core/journals/radiocarbon/article/modeling-the-carbon-system/5379951AF625C8A15696E4E52DE79BD6

1981

Glacial to Interglacial Changes in Ocean and Atmosphere Chemistry https://link.springer.com/chapter/10.1007/978-94-009-8514-8_5

1982

Ocean chemistry during glacial time https://www.sciencedirect.com/science/article/pii/0016703782901107

1984

Terminations https://link.springer.com/chapter/10.1007/978-94-017-4841-4_14

Is There A Tie Between Atmospheric CO2 Content and Ocean Circulation? https://www.cambridge.org/core/journals/annals-of-glaciology/article/is-there-a-tie-between-atmospheric-co2-content-and-ocean-circulation-abstract/4C4FE09E12D93C25A2003F1F3BE16EE3

Radiocarbon measurements on coexisting benthic and planktic foraminifera shells: potential for reconstructing ocean ventilation times over the past 20 000 years https://www.sciencedirect.com/science/article/pii/0168583X8490538X

1985

Does the ocean–atmosphere system have more than one stable mode of operation? https://www.nature.com/articles/315021a0

Sources and flow patterns of deep‐ocean waters as deduced from potential temperature, salinity, and initial phosphate concentration https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JC090iC04p06925

1986

Carbon Cycle: 1985 Glacial to Interglacial Changes in the Operation of the Global Carbon Cycle https://www.cambridge.org/core/journals/radiocarbon/article/carbon-cycle-1985-glacial-to-interglacial-changes-in-the-operation-of-the-global-carbon-cycle/453E35DB3657CEF83F8B9E247287FF38

Hydrography, chemistry, and radioisotopes in the Southeast Asian basins https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JC091iC12p14345

1987

Unpleasant surprises in the greenhouse? https://www.nature.com/articles/328123a0

1988

New evidence from the South China Sea for an abrupt termination of the last glacial period https://www.nature.com/articles/333156a0

Can the Greenland Climatic Jumps be Identified in Records from Ocean and Land? https://www.cambridge.org/core/journals/quaternary-research/article/can-the-greenland-climatic-jumps-be-identified-in-records-from-ocean-and-land/3717F76BA966C1A7E4B51E96891F6033

The chronology of the last Deglaciation: Implications to the cause of the Younger Dryas Event https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/PA003i001p00001

1989

The role of ocean-atmosphere reorganizations in glacial cycles https://www.sciencedirect.com/science/article/pii/0016703789901233

The salinity contrast between the Atlantic and Pacific oceans during glacial time https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/PA004i002p00207

Some thoughts about the radiocarbon budget for the glacial Atlantic https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/PA004i002p00213

1990

The role of ocean-atmosphere reorganizations in glacial cycles https://www.sciencedirect.com/science/article/abs/pii/0277379190900267

The magnitude of global fresh-water transports of importance to ocean circulation https://link.springer.com/article/10.1007/BF00208902

The magnitude of global fresh-water transports of importance to ocean circulation https://link.springer.com/article/10.1007/BF00208902

A salt oscillator in the glacial Atlantic? 1. The concept https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/PA005i004p00469

The distribution of radiocarbon in the glacial ocean https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/GB004i001p00103

Salinity history of the northern Atlantic during the last deglaciation https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/PA005i004p00459

1991

The Great Ocean Conveyor https://www.jstor.org/stable/43924572

Keeping global change honest https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/91GB01421

The Influence of CaCO3 Dissolution on Core Top Radiocarbon Ages for Deep‐Sea Sediments https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/91PA01768

Radiocarbon age of waters in the deep Atlantic revisited https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/90GL02707

1992

Origin of the northern Atlantic’s Heinrich events https://link.springer.com/article/10.1007/BF00193540

The influence of air and sea exchange on the carbon isotope distribution in the sea https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/92GB01672

Defining the Boundaries of the Late-Glacial Isotope Episodes https://www.cambridge.org/core/journals/quaternary-research/article/defining-the-boundaries-of-the-lateglacial-isotope-episodes/ED0290CB6C9734A818CFE909CCEFB312

Interhemispheric transport of carbon dioxide by ocean circulation https://www.nature.com/articles/356587a0

1993

Heinrich Events: Triggers of Ocean Circulation Change? https://link.springer.com/chapter/10.1007/978-3-642-85016-5_10

A Search for an Early Holocene CACO3 Preservation Event https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/93PA00423

What Caused the Glacial to Interglacial CO2 Change? https://link.springer.com/chapter/10.1007/978-3-642-84608-3_4

Evaluation of the 13C constraint on the uptake of fossil fuel CO2 by the ocean https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/93GB01445

Interhemispheric Transport of Carbon Through the Ocean https://link.springer.com/chapter/10.1007/978-3-642-84608-3_22

1994

Massive iceberg discharges as triggers for global climate change https://www.nature.com/articles/372421a0

1996

Glacial Climate in the Tropics http://science.sciencemag.org/content/272/5270/1902

1997

Thermohaline Circulation, the Achilles Heel of Our Climate System: Will Man-Made CO2 Upset the Current Balance? http://science.sciencemag.org/content/278/5343/1582

Future directions of paleoclimate research https://www.sciencedirect.com/science/article/abs/pii/S0277379197000504

Will Our Ride into the Greenhouse Future be a Smooth One? http://oceanrep.geomar.de/33087/

Mountain glaciers: Recorders of atmospheric water vapor content? https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/97GB02267

Magnitude of the CaCO3 dissolution events marking the onset of times of glaciation https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/97PA01020

1998

The end of the present interglacial: How and when? https://www.sciencedirect.com/science/article/abs/pii/S0277379198000377

Does atmospheric CO2 police the rate of chemical weathering? https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/98GB01927

Paleocean circulation during the Last Deglaciation: A bipolar seesaw? https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/97PA03707

Antiphasing between Rainfall in Africa’s Rift Valley and North America’s Great Basin https://www.cambridge.org/core/journals/quaternary-research/article/antiphasing-between-rainfall-in-africas-rift-valley-and-north-americas-great-basin/9B1EE73D21721A2EEFD0F1897034E52E

The sequence of events surrounding Termination II and their implications for the cause of glacial‐interglacial CO2 changes https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/98PA00920

1999

Climate Change Prediction http://science.sciencemag.org/content/283/5399/175.6

A Possible 20th-Century Slowdown of Southern Ocean Deep Water Formation http://science.sciencemag.org/content/286/5442/1132

CaCO3 size distribution: A paleocarbonate ion proxy? https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999PA900016

How strong is the Harvardton‐Bear Constraint? https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999GB900050

What If the Conveyor Were to Shut Down? Reflections on a Possible Outcome of the Great Global Experiment ftp://rock.geosociety.org/pub/gsatoday/gt9901.pdf

Core Top 14C Ages as a Function of Latitude and Water Depth on the Ontong‐Java Plateau https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1998PA900009

2000

Abrupt climate change: causal constraints provided by the paleoclimate record https://www.sciencedirect.com/science/article/pii/S0012825200000192

Was a change in thermohaline circulation responsible for the Little Ice Age? https://www.pnas.org/content/97/4/1339.short

Converging Paths Leading to the Role of the Oceans in Climate Change https://www.annualreviews.org/doi/full/10.1146/annurev.energy.25.1.1

Late glacial diatom accumulation at 9°S in the Indian Ocean https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999PA000439

2001

Climate Swings Come into Focus http://science.sciencemag.org/content/294/5550/2308

Was the Medieval Warm Period Global? http://science.sciencemag.org/content/291/5508/1497

What caused the atmosphere’s CO2 content to rise during the last 8000 years? https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001GC000177

Rock varnish: recorder of desert wetness? https://www.geosociety.org/gsatoday/archive/11/8/pdf/i1052-5173-11-8-4.pdf

A dramatic Atlantic dissolution event at the onset of the last glaciation https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001GC000185

Reevaluation of the CaCO3 size index paleocarbonate ion proxy https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2001PA000660

Record of seafloor CaCO3 dissolution in the central equatorial Pacific https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2000GC000151

2002

Dust: Climate’s Rosetta Stone https://www.jstor.org/stable/1558157

Constraints on the glacial operation of the atlantic ocean’s conveyor circulation https://onlinelibrary.wiley.com/doi/abs/10.1560/8K19-VRHE-6F14-PFQQ

Carbonate ion concentration in glacial‐age deep waters of the Caribbean Sea https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2001GC000231

2003

Does the Trigger for Abrupt Climate Change Reside in the Ocean or in the Atmosphere? http://science.sciencemag.org/content/300/5625/1519

Holocene atmospheric CO2 increase as viewed from the seafloor https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2002GB001985

Shell weights from intermediate depths in the Caribbean Sea https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2002GC000491

2004

Future Global Warming Scenarios http://science.sciencemag.org/content/304/5669/388.2

Glacial ventilation rates for the deep Pacific Ocean https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2003PA000974

Ventilation of the Glacial Deep Pacific Ocean http://science.sciencemag.org/content/306/5699/1169

2006

Abrupt climate change revisited https://www.sciencedirect.com/science/article/pii/S092181810600186X

The Holocene CO2 rise: Anthropogenic or natural? https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2006EO030002

Was the Younger Dryas Triggered by a Flood? http://science.sciencemag.org/content/312/5777/1146

Global warming: Take action or wait? https://link.springer.com/article/10.1007/s11434-006-1017-4

2007

CO2 Arithmetic http://science.sciencemag.org/content/315/5817/1371

Radiocarbon age of late glacial deep water from the equatorial Pacific https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006PA001359

A 190‰ drop in atmosphere’s Δ14C during the “Mystery Interval” (17.5 to 14.5 kyr) https://www.sciencedirect.com/science/article/pii/S0012821X07000313

Is the magnitude of the carbonate ion decrease in the abyssal ocean over the last 8 kyr consistent with the 20 ppm rise in atmospheric CO2 content? https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006PA001311

2008

Near constancy of the Pacific Ocean surface to mid-depth radiocarbon-age difference over the last 20 kyr https://www.sciencedirect.com/science/article/pii/S0012821X08004780

A need to improve reconstructions of the fluctuations in the calcite compensation depth over the course of the Cenozoic https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2007PA001456

2009

A Great Basin-wide dry episode during the first half of the Mystery Interval? https://www.sciencedirect.com/science/article/abs/pii/S0277379109002509

The Mysterious 14C Decline https://www.cambridge.org/core/journals/radiocarbon/article/mysterious-14c-decline/61A16C59506B7D1B570A51A4EF3C05D3

Wally’s Quest to Understand the Ocean’s CaCO3 Cycle https://www.annualreviews.org/doi/full/10.1146/annurev.marine.010908.163936

2010

Putting the Younger Dryas cold event into context https://www.sciencedirect.com/science/article/abs/pii/S027737911000051X

Long-Term Water Prospects in the Western United States https://journals.ametsoc.org/doi/full/10.1175/2010JCLI3780.1

Search for a glacial‐age 14C‐depleted ocean reservoir https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL043969

2012

The Carbon Cycle and Climate Change: Memoirs of my 60 years in Science https://pubs.geoscienceworld.org/perspectives/article-abstract/1/2/221/138762

How did the hydrologic cycle respond to the two-phase mystery interval? https://www.sciencedirect.com/science/article/abs/pii/S0277379112003757

2013

Hydrologic impacts of past shifts of Earth’s thermal equator offer insight into those to be produced by fossil fuel CO2 https://www.pnas.org/content/110/42/16710.short

2014

Delayed Holocene reappearance of G. menardii https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013PA002590

2015

Two contributors to the glacial CO2 decline https://www.sciencedirect.com/science/article/pii/S0012821X1500446X

2017

When climate change predictions are right for the wrong reasons https://link.springer.com/article/10.1007/s10584-017-1927-y

2018

CO2: Earth’s Climate Driver https://pubs.geoscienceworld.org/perspectives/article-abstract/7/2/117/567159

List of Papers on Global Warming Hiatus, v2.0 (308 papers)

I have updated my list of papers on global warming hiatus to include papers published during 2017. There are also a few additions of earlier published papers.

The paper count is now 308.

The list can be downloaded from ResearchGate:

List of Global Warming Hiatus Papers, version 2
https://www.researchgate.net/publication/329982489_List_of_Global_Warming_Hiatus_Papers_version_2

DOI: 10.13140/RG.2.2.29065.70241

Papers on California wildfires

This is a list of papers on California wildfires with an emphasis on climate related papers. The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Distribution and frequency of wildfire in California riparian ecosystems (Bendix and Commons, 2017) [FULL TEXT]
Abstract: “Although wildfire has been recognized as having important ecological impacts on California’s riparian environments, understanding of its occurrence is largely anecdotal, based on studies of fire impacts in scattered locations. In this paper we use data for 21 years of wildfires to examine the distribution, seasonality and climatic context of riparian wildfire across the state. We used the Monitoring Trends in Burn Severity and LANDFIRE databases to identify fires that had burned in areas classified as having riparian vegetation, and matched those fires with the Fire and Resource Assessment Program database to determine the date of occurrence of each. From 1990 through 2010, an average of 1197 ha of riparian vegetation burned per year, which extrapolates to a fire return interval of 843 years. The statewide totals are misleading, however, because there is substantial geographic variance in the occurrence of riparian fire. In southern California ecoregions, extrapolated return intervals are as low as 74 years, contrasting with the Basin and Range ecoregions, where return intervals exceed 1000 years. Moreover, there is substantial geographic variation in the season of riparian fire, and in the relationship between fire occurrence and climatic variables. Both the widespread occurrence of riparian fire and its spatial variability are potentially important for management of critical riparian habitat.”
Citation: Jacob Bendix and Michael G Commons 2017 Environ. Res. Lett. 12 075008, https://doi.org/10.1088/1748-9326/aa7087.

Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California (Mann et al. 2016) [FULL TEXT]
Abstract: “The costly interactions between humans and wildfires throughout California demonstrate the need to understand the relationships between them, especially in the face of a changing climate and expanding human communities. Although a number of statistical and process-based wildfire models exist for California, there is enormous uncertainty about the location and number of future fires, with previously published estimates of increases ranging from nine to fifty-three percent by the end of the century. Our goal is to assess the role of climate and anthropogenic influences on the state’s fire regimes from 1975 to 2050. We develop an empirical model that integrates estimates of biophysical indicators relevant to plant communities and anthropogenic influences at each forecast time step. Historically, we find that anthropogenic influences account for up to fifty percent of explanatory power in the model. We also find that the total area burned is likely to increase, with burned area expected to increase by 2.2 and 5.0 percent by 2050 under climatic bookends (PCM and GFDL climate models, respectively). Our two climate models show considerable agreement, but due to potential shifts in rainfall patterns, substantial uncertainty remains for the semiarid inland deserts and coastal areas of the south. Given the strength of human-related variables in some regions, however, it is clear that comprehensive projections of future fire activity should include both anthropogenic and biophysical influences. Previous findings of substantially increased numbers of fires and burned area for California may be tied to omitted variable bias from the exclusion of human influences. The omission of anthropogenic variables in our model would overstate the importance of climatic ones by at least 24%. As such, the failure to include anthropogenic effects in many models likely overstates the response of wildfire to climatic change.”
Citation: Mann ML, Batllori E, Moritz MA, Waller EK, Berck P, Flint AL, et al. (2016) Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California. PLoS ONE 11(4): e0153589. https://doi.org/10.1371/journal.pone.0153589.

Large wildfire trends in the western United States, 1984–2011 (Dennison et al. 2014) [FULL TEXT]
Abstract: “We used a database capturing large wildfires (> 405 ha) in the western U.S. to document regional trends in fire occurrence, total fire area, fire size, and day of year of ignition for 1984–2011. Over the western U.S. and in a majority of ecoregions, we found significant, increasing trends in the number of large fires and/or total large fire area per year. Trends were most significant for southern and mountain ecoregions, coinciding with trends toward increased drought severity. For all ecoregions combined, the number of large fires increased at a rate of seven fires per year, while total fire area increased at a rate of 355 km2 per year. Continuing changes in climate, invasive species, and consequences of past fire management, added to the impacts of larger, more frequent fires, will drive further disruptions to fire regimes of the western U.S. and other fire‐prone regions of the world.”
Citation: Dennison, P. E., S. C. Brewer, J. D. Arnold, and M. A. Moritz (2014), Large wildfire trends in the western United States, 1984–2011, Geophys. Res. Lett., 41, 2928–2933, doi: 10.1002/2014GL059576.

Trends in wildfire severity: 1984 to 2010 in the Sierra Nevada, Modoc Plateau, and southern Cascades, California, USA (Miller and Safford, 2012) [FULL TEXT]
Abstract: “Data from recent assessments indicate that the annual area of wildfires burning at high severity (where most trees are killed) has increased since 1984 across much of the southwestern United States. Increasing areas of high-severity fire can occur when greater area is burned at constant proportion of high-severity fire, or when the proportion of high-severity fire within fire perimeters increases, or some combination of both. For the Sierra Nevada Forest Plan Amendment (SNFPA) area, which includes forestlands in eastern California and western Nevada, Miller et al. (2009a) concluded that the proportion of area burning at high severity in mixed-conifer forests had risen over the 1984 to 2004 period. However, no statistical assessment was made of the temporal trend in high-severity fire area because the analyzed dataset was incomplete in the early years of the study period. In this update, we use satellite-derived estimates of fire severity from the three most widely distributed SNFPA forest types to examine the trend in percent high severity and highseverity fire area for all wildfires ≥80 ha that occurred during the 1984 to 2010 period. Time-series regression modeling indicates that the percentage of total high severity per year for a combination of yellow pine (ponderosa pine [Pinus ponderosa Lawson & C. Lawson] or Jeffrey pine [P. jeffreyi Balf.]) and mixed-conifer forests increased significantly over the 27-year period. The annual area of high-severity fire also increased significantly in yellow pine-mixed-conifer forests. The percentage of high severity in fires ≥400 ha burning in yellow pine-mixed-conifer forests was significantly higher than in fires <400 ha. Additionally, the number of fires ≥400 ha significantly increased over the 1950 to 2010 period. There were no significant trends in red fir (Abies magnifica A. Murray bis) forests. These results confirm and expand our earlier published results for a shorter 21-year period."
Citation: Jay D. Miller, Hugh Safford, Fire Ecology, 8(3), doi: 10.4996/fireecology.0803041.

Climate change and growth scenarios for California wildfire (Westerling et al. 2011) [FULL TEXT]
Abstract: “Large wildfire occurrence and burned area are modeled using hydroclimate and landsurface characteristics under a range of future climate and development scenarios. The range of uncertainty for future wildfire regimes is analyzed over two emissions pathways (the Special Report on Emissions Scenarios [SRES] A2 and B1 scenarios); three global climate models (Centre National de Recherches Météorologiques CM3, Geophysical Fluid Dynamics Laboratory CM2.1 and National Center for Atmospheric Research PCM1); three scenarios for future population growth and development footprint; and two thresholds for defining the wildland-urban interface relative to housing density. Results were assessed for three 30-year time periods centered on 2020, 2050, and 2085, relative to a 30-year reference period centered on 1975. Increases in wildfire burned area are anticipated for most scenarios, although the range of outcomes is large and increases with time. The increase in wildfire burned area associated with the higher emissions pathway (SRES A2) is substantial, with increases statewide ranging from 36% to 74% by 2085, and increases exceeding 100% in much of the forested areas of Northern California in every SRES A2 scenario by 2085.”
Citation: Westerling, A.L., Bryant, B.P., Preisler, H.K. et al. Climatic Change (2011) 109(Suppl 1): 445. https://doi.org/10.1007/s10584-011-0329-9.

Paleofire reconstruction for high-elevation forests in the Sierra Nevada, California, with implications for wildfire synchrony and climate variability in the late Holocene (Hallett and Anderson, 2010) [FULL TEXT]
Abstract: “Here, we present two high-resolution records of macroscopic charcoal from high-elevation lake sites in the Sierra Nevada, California, and evaluate the synchroneity of fire response for east- and west-side subalpine forests during the past 9200 yr. Charcoal influx was low between 11,200 and 8000 cal yr BP when vegetation consisted of sparse Pinus-dominated forest and montane chaparral shrubs. High charcoal influx after 8000 cal yr BP marks the arrival of Tsuga mertensiana and Abies magnifica, and a higher-than-present treeline that persisted into the mid-Holocene. Coeval decreases in fire episode frequency coincide with neoglacial advances and lower treeline in the Sierra Nevada after 3800 cal yr BP. Independent fire response occurs between 9200 and 5000 cal yr BP, and significant synchrony at 100- to 1000-yr timescales emerges between 5000 cal yr BP and the present, especially during the last 2500 yr. Indistinguishable fire-return interval distributions and synchronous fires show that climatic control of fire became increasingly important during the late Holocene. Fires after 1200 cal yr BP are often synchronous and corroborate with inferred droughts. Holocene fire activity in the high Sierra Nevada is driven by changes in climate linked to insolation and appears to be sensitive to the dynamics of the El Niño–Southern Oscillation.”
Citation: Hallett, D., & Anderson, R. (2010). Paleofire reconstruction for high-elevation forests in the Sierra Nevada, California, with implications for wildfire synchrony and climate variability in the late Holocene. Quaternary Research, 73(2), 180-190. doi:10.1016/j.yqres.2009.11.008.

Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States (Spracklen et al. 2009) [FULL TEXT]
Abstract: “We investigate the impact of climate change on wildfire activity and carbonaceous aerosol concentrations in the western United States. We regress observed area burned onto observed meteorological fields and fire indices from the Canadian Fire Weather Index system and find that May–October mean temperature and fuel moisture explain 24–57% of the variance in annual area burned in this region. Applying meteorological fields calculated by a general circulation model (GCM) to our regression model, we show that increases in temperature cause annual mean area burned in the western United States to increase by 54% by the 2050s relative to the present day. Changes in area burned are ecosystem dependent, with the forests of the Pacific Northwest and Rocky Mountains experiencing the greatest increases of 78 and 175%, respectively. Increased area burned results in near doubling of wildfire carbonaceous aerosol emissions by midcentury. Using a chemical transport model driven by meteorology from the same GCM, we calculate that climate change will increase summertime organic carbon (OC) aerosol concentrations over the western United States by 40% and elemental carbon (EC) concentrations by 20% from 2000 to 2050. Most of this increase (75% for OC and 95% for EC) is caused by larger wildfire emissions with the rest caused by changes in meteorology and for OC by increased monoterpene emissions in a warmer climate. Such an increase in carbonaceous aerosol would have important consequences for western U.S. air quality and visibility.”
Citation: Spracklen, D. V., L. J. Mickley, J. A. Logan, R. C. Hudman, R. Yevich, M. D. Flannigan, and A. L. Westerling (2009), Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States, J. Geophys. Res., 114, D20301, doi: 10.1029/2008JD010966.

Environmental controls on the distribution of wildfire at multiple spatial scales (Parisien and Moritz, 2009) [FULL TEXT]
Abstract: “Despite its widespread occurrence globally, wildfire preferentially occupies an environmental middle ground and is significantly less prevalent in biomes characterized by environmental extremes (e.g., tundra, rain forests, and deserts). We evaluated the biophysical “environmental space” of wildfire from regional to subcontinental extents, with methods widely used for modeling habitat distributions. This approach is particularly suitable for the biogeographic study of wildfire, because it simultaneously considers patterns in multiple factors controlling wildfire suitability over large areas. We used the Maxent and boosted regression tree algorithms to assess wildfire–environment relationships for three levels of complexity (in terms of inclusion of variables) at three spatial scales: the conterminous United States, the state of California, and five wildfire‐prone ecoregions of California. The resulting models were projected geographically to obtain spatial predictions of wildfire suitability and were also applied to other regions to assess their generality and spatial transferability. Predictions of the potential range of wildfire had high classification accuracy; they also highlighted areas where wildfires had not recently been observed, indicating the potential (or past) suitability of these areas. The models identified several key variables that were not suspected to be important in the large‐scale control of wildfires, but which might indirectly affect control by influencing the presence of flammable vegetation. Models transferred to different areas were useful only when they overlapped appreciably with the target area’s environmental space. This approach should allow exploration of the potential shifts in wildfire range in a changing climate, the potential for restoration of wildfire where it has been “extirpated,” and, conversely, the “invasiveness” of wildfire after changes in plant species composition. Our study demonstrates that habitat distribution models and related concepts can be used to characterize environmental controls on a natural disturbance process, but also that future work is needed to refine our understanding of the direct causal factors controlling wildfire at multiple spatial scales.”
Citation: Parisien, M. and Moritz, M. A. (2009), Environmental controls on the distribution of wildfire at multiple spatial scales. Ecological Monographs, 79: 127-154. doi:10.1890/07-1289.1.

Climate and wildfire area burned in western U.S. ecoprovinces, 1916–2003 (Littell et al. 2009) [FULL TEXT]
Abstract: “The purpose of this paper is to quantify climatic controls on the area burned by fire in different vegetation types in the western United States. We demonstrate that wildfire area burned (WFAB) in the American West was controlled by climate during the 20th century (1916–2003). Persistent ecosystem‐specific correlations between climate and WFAB are grouped by vegetation type (ecoprovinces). Most mountainous ecoprovinces exhibit strong year‐of‐fire relationships with low precipitation, low Palmer drought severity index (PDSI), and high temperature. Grass‐ and shrub‐dominated ecoprovinces had positive relationships with antecedent precipitation or PDSI. For 1977–2003, a few climate variables explain 33–87% (mean = 64%) of WFAB, indicating strong linkages between climate and area burned. For 1916–2003, the relationships are weaker, but climate explained 25–57% (mean = 39%) of the variability. The variance in WFAB is proportional to the mean squared for different data sets at different spatial scales. The importance of antecedent climate (summer drought in forested ecosystems and antecedent winter precipitation in shrub and grassland ecosystems) indicates that the mechanism behind the observed fire–climate relationships is climatic preconditioning of large areas of low fuel moisture via drying of existing fuels or fuel production and drying. The impacts of climate change on fire regimes will therefore vary with the relative energy or water limitations of ecosystems. Ecoprovinces proved a useful compromise between ecologically imprecise state‐level and localized gridded fire data. The differences in climate–fire relationships among the ecoprovinces underscore the need to consider ecological context (vegetation, fuels, and seasonal climate) to identify specific climate drivers of WFAB. Despite the possible influence of fire suppression, exclusion, and fuel treatment, WFAB is still substantially controlled by climate. The implications for planning and management are that future WFAB and adaptation to climate change will likely depend on ecosystem‐specific, seasonal variation in climate. In fuel‐limited ecosystems, fuel treatments can probably mitigate fire vulnerability and increase resilience more readily than in climate‐limited ecosystems, in which large severe fires under extreme weather conditions will continue to account for most area burned.”
Citation: Littell, J. S., McKenzie, D. , Peterson, D. L. and Westerling, A. L. (2009), Climate and wildfire area burned in western U.S. ecoprovinces, 1916–2003. Ecological Applications, 19: 1003-1021. doi:10.1890/07-1183.1.

Climate change and wildfire in California (Westerling and Bryant, 2008) [FULL TEXT]
Abstract: “Wildfire risks for California under four climatic change scenarios were statistically modeled as functions of climate, hydrology, and topography. Wildfire risks for the GFDL and PCM global climate models and the A2 and B1 emissions scenarios were compared for 2005–2034, 2035–2064, and 2070–2099 against a modeled 1961–1990 reference period in California and neighboring states. Outcomes for the GFDL model runs, which exhibit higher temperatures than the PCM model runs, diverged sharply for different kinds of fire regimes, with increased temperatures promoting greater large fire frequency in wetter, forested areas, via the effects of warmer temperatures on fuel flammability. At the same time, reduced moisture availability due to lower precipitation and higher temperatures led to reduced fire risks in some locations where fuel flammability may be less important than the availability of fine fuels. Property damages due to wildfires were also modeled using the 2000 U.S. Census to describe the location and density of residential structures. In this analysis the largest changes in property damages under the climate change scenarios occurred in wildland/urban interfaces proximate to major metropolitan areas in coastal southern California, the Bay Area, and in the Sierra foothills northeast of Sacramento.”
Citation: Westerling, A.L. & Bryant, B.P. Climatic Change (2008) 87(Suppl 1): 231. https://doi.org/10.1007/s10584-007-9363-z.

Human influence on California fire regimes (Syphard et al. 2007) [FULL TEXT]
Abstract: “Periodic wildfire maintains the integrity and species composition of many ecosystems, including the mediterranean‐climate shrublands of California. However, human activities alter natural fire regimes, which can lead to cascading ecological effects. Increased human ignitions at the wildland–urban interface (WUI) have recently gained attention, but fire activity and risk are typically estimated using only biophysical variables. Our goal was to determine how humans influence fire in California and to examine whether this influence was linear, by relating contemporary (2000) and historic (1960–2000) fire data to both human and biophysical variables. Data for the human variables included fine‐resolution maps of the WUI produced using housing density and land cover data. Interface WUI, where development abuts wildland vegetation, was differentiated from intermix WUI, where development intermingles with wildland vegetation. Additional explanatory variables included distance to WUI, population density, road density, vegetation type, and ecoregion. All data were summarized at the county level and analyzed using bivariate and multiple regression methods. We found highly significant relationships between humans and fire on the contemporary landscape, and our models explained fire frequency (R2 = 0.72) better than area burned (R2 = 0.50). Population density, intermix WUI, and distance to WUI explained the most variability in fire frequency, suggesting that the spatial pattern of development may be an important variable to consider when estimating fire risk. We found nonlinear effects such that fire frequency and area burned were highest at intermediate levels of human activity, but declined beyond certain thresholds. Human activities also explained change in fire frequency and area burned (1960–2000), but our models had greater explanatory power during the years 1960–1980, when there was more dramatic change in fire frequency. Understanding wildfire as a function of the spatial arrangement of ignitions and fuels on the landscape, in addition to nonlinear relationships, will be important to fire managers and conservation planners because fire risk may be related to specific levels of housing density that can be accounted for in land use planning. With more fires occurring in close proximity to human infrastructure, there may also be devastating ecological impacts if development continues to grow farther into wildland vegetation.”
Citation: Syphard, A. D., Radeloff, V. C., Keeley, J. E., Hawbaker, T. J., Clayton, M. K., Stewart, S. I. and Hammer, R. B. (2007), HUMAN INFLUENCE ON CALIFORNIA FIRE REGIMES. Ecological Applications, 17: 1388-1402. doi:10.1890/06-1128.1.

Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity (Westerling et al. 2006) [FULL TEXT]
Abstract: “Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.”
Citation: A. L. Westerling, H. G. Hidalgo, D. R. Cayan, T. W. Swetnam, Science 18 Aug 2006: Vol. 313, Issue 5789, pp. 940-943, DOI: 10.1126/science.1128834.

Climate change projected fire weather sensitivity: California Santa Ana wind occurrence (Miller and Schlegel, 2006) [FULL TEXT]
Abstract: “A new method based on global climate model pressure gradients was developed for identifying coastal high‐wind fire weather conditions, such as the Santa Ana Occurrence (SAO). Application of this method for determining southern California Santa Ana wind occurrence resulted in a good correlation between derived large‐scale SAOs and observed offshore winds during periods of low humidity. The projected change in the number of SAOs was analyzed using two global climate models, one a low temperature sensitivity and the other a middle‐temperature sensitivity, both forced with low and high emission scenarios, for three future time periods. This initial analysis shows consistent shifts in SAO events from earlier (September–October) to later (November–December) in the season, suggesting that SAOs may significantly increase the extent of California coastal areas burned by wildfires, loss of life, and property.”
Citation: Spracklen, D. V., L. J. Mickley, J. A. Logan, R. C. Hudman, R. Yevich, M. D. Flannigan, and A. L. Westerling (2009), Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States, J. Geophys. Res., 114, D20301, doi: 10.1029/2008JD010966.

The Impact of Climate Change on Wildfire Severity: A Regional Forecast for Northern California (Fried et al. 2004) [FULL TEXT]
Abstract: “We estimated the impact of climatic change on wildland fire and suppression effectiveness in northern California by linking general circulation model output to local weather and fire records and projecting fire outcomes with an initial-attack suppression model. The warmer and windier conditions corresponding to a 2 × CO2 climate scenario produced fires that burned more intensely and spread faster in most locations. Despite enhancement of fire suppression efforts, the number of escaped fires (those exceeding initial containment limits) increased 51% in the south San Francisco Bay area, 125% in the Sierra Nevada, and did not change on the north coast. Changes in area burned by contained fires were 41%, 41% and –8%, respectively. When interpolated to most of northern California’s wildlands, these results translate to an average annual increase of 114 escapes (a doubling of the current frequency) and an additional 5,000 hectares (a 50% increase) burned by contained fires. On average, the fire return intervals in grass and brush vegetation types were cut in half. The estimates reported represent a minimum expected change, or best-case forecast. In addition to the increased suppression costs and economic damages, changes in fire severity of this magnitude would have widespread impacts on vegetation distribution, forest condition, and carbon storage, and greatly increase the risk to property, natural resources and human life.”
Citation: Fried, J.S., Torn, M.S. & Mills, E. Climatic Change (2004) 64: 169. https://doi.org/10.1023/B:CLIM.0000024667.89579.ed.

Climate and Wildfire in the Western United States (Westerling et al. 2003) [FULL TEXT]
Abstract: “A 21-yr gridded monthly fire-starts and acres-burned dataset from U.S. Forest Service, Bureau of Land Management, National Park Service, and Bureau of Indian Affairs fire reports recreates the seasonality and interannual variability of wild fire in the western United States. Despite pervasive human influence in western fire regimes, it is striking how strongly these data reveal a fire season responding to variations in climate. Correlating anomalous wildfire frequency and extent with the Palmer Drought Severity Index illustrates the importance of prior and accumulated precipitation anomalies for future wildfire season severity. This link to antecedent seasons’ moisture conditions varies widely with differences in predominant fuel type. Furthermore, these data demonstrate that the relationship between wildfire season severity and observed moisture anomalies from antecedent seasons is strong enough to forecast fire season severity at lead times of one season to a year in advance.”
Citation: Westerling, A.L., A. Gershunov, T.J. Brown, D.R. Cayan, and M.D. Dettinger, 2003: Climate and Wildfire in the Western United States. Bull. Amer. Meteor. Soc., 84, 595–604, https://doi.org/10.1175/BAMS-84-5-595.

Climate change effects on vegetation distribution, carbon, and fire in California (Lenihan et al. 2003) [FULL TEXT]
Abstract: “The objective of this study was to dynamically simulate the response of vegetation distribution, carbon, and fire to the historical climate and to two contrasting scenarios of climate change in California. The results of the simulations for the historical climate compared favorably to independent estimates and observations, but validation of the results was complicated by the lack of land use effects in the model. The response to increasing temperatures under both scenarios was characterized by a shift in dominance from needle‐leaved to broad‐leaved life‐forms and by increases in vegetation productivity, especially in the relatively cool and mesic regions of the state. The simulated response to changes in precipitation were complex, involving not only the effect of changes in soil moisture on vegetation productivity, but also changes in tree–grass competition mediated by fire. Summer months were warmer and persistently dry under both scenarios, so the trends in simulated fire area under both scenarios were primarily a response to changes in vegetation biomass. Total ecosystem carbon increased under both climate scenarios, but the proportions allocated to the wood and grass carbon pools differed. The results of the simulations underscore the potentially large impact of climate change on California ecosystems, and the need for further use and development of dynamic vegetation models using various ensembles of climate change scenarios.”
Citation: Lenihan, J. M., Drapek, R. , Bachelet, D. and Neilson, R. P. (2003), CLIMATE CHANGE EFFECTS ON VEGETATION DISTRIBUTION, CARBON, AND FIRE IN CALIFORNIA. Ecological Applications, 13: 1667-1681. doi:10.1890/025295.

Global warming hiatus paper list, version 1.0 (224 papers), part 2

Continued from part 1.

Papers 100 – 225

NR – 100
TY – JOUR
AU – Thorne, Peter
AU – Outten, Stephen
AU – Bethke, Ingo
AU – Seland, Øyvind
TI – Investigating the recent apparent hiatus in surface temperature increases: 2. Comparison of model ensembles to observational estimates
JO – Journal of Geophysical Research: Atmospheres
VL – 120
IS – 17
UR – http://dx.doi.org/10.1002/2014JD022805
DO – 10.1002/2014JD022805
SP – 8597
EP – 8620
PY – 2015
AB – To assess published hypotheses surrounding the recent slowdown in surface warming (hiatus), we compare five available global observational surface temperature estimates to two 30-member ensembles from the Norwegian Earth System Model (NorESM). Model ensembles are initialized in 1980 from the transient historical runs and driven with forcings used in the CMIP5 experiments and updated forcings based upon current observational understanding, described in Part 1. The ensembles’ surface temperature trends are statistically indistinguishable over 1998–2012 despite differences in the prescribed forcings. There is thus no evidence that forcing errors play a significant role in explaining the hiatus according to NorESM. The observations fall either toward the lower portion of the ensembles or, for some observational estimates and regions, outside. The exception is the Arctic where the observations fall toward the upper ensemble bounds. Observational data set choices can make a large difference to findings of consistency or otherwise. Those NorESM ensemble members that exhibit Nino3.4 Sea Surface Temperature (SST) trends similar to observed also exhibit comparable tropical and to some extent global mean trends, supporting a role for El Nino Southern Oscillation in explaining the hiatus. Several ensemble members capture the marked seasonality observed in Northern Hemisphere midlatitude trends, with cooling in the wintertime and warming in the remaining seasons. Overall, we find that we cannot falsify NorESM as being capable of explaining the observed hiatus behavior. Importantly, this is not equivalent to concluding NorESM could simultaneously capture all important facets of the hiatus. Similar experiments with further, distinct, Earth System Models are required to verify our findings.
ER –

NR – 101
TY – JOUR
AU – Fyfe, John C.
AU – Meehl, Gerald A.
AU – England, Matthew H.
AU – Mann, Michael E.
AU – Santer, Benjamin D.
AU – Flato, Gregory M.
AU – Hawkins, Ed
AU – Gillett, Nathan P.
AU – Xie, Shang-Ping
AU – Kosaka, Yu
AU – Swart, Neil C.
TI – Making sense of the early-2000s warming slowdown
JF – Nature Climate Change
PY – 2016
VL – 6
SP – 224
UR – http://dx.doi.org/10.1038/nclimate2938
DO – 10.1038/nclimate2938
AB – It has been claimed that the early-2000s global warming slowdown or hiatus, characterized by a reduced rate of global surface warming, has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims.
ER –

NR – 102
TY – JOUR
AU – Boykoff, Maxwell T.
TI – Media discourse on the climate slowdown
JF – Nature Climate Change
PY – 2014
VL – 4
SP – 156
UR – http://dx.doi.org/10.1038/nclimate2156
DO – 10.1038/nclimate2156
AB – We must not fall victim to decontextualized and ahistorical media accounting of climate trends.
ER –

NR – 103
TY – JOUR
AU – Somavilla, R.
AU – González-Pola, C.
AU – Schauer, U.
AU – Budéus, G.
TI – Mid-2000s North Atlantic shift: Heat budget and circulation changes
JO – Geophysical Research Letters
VL – 43
IS – 5
UR – http://dx.doi.org/10.1002/2015GL067254
DO – 10.1002/2015GL067254
SP – 2059
EP – 2068
PY – 2016
AB – Prior to the 2000s, the North Atlantic was the basin showing the greatest warming. However, since the mid-2000s during the so-called global warming hiatus, large amounts of heat were transferred in this basin from upper to deeper levels while the dominance in terms of atmospheric heat capture moved into the Indo-Pacific. Here we show that a large transformation of modal waters in the eastern North Atlantic (ENA) played a crucial role in such contrasting behavior. First, strong winter mixing in 2005 transformed ENA modal waters into a much saltier, warmer, and denser variety, transferring upper ocean heat and salt gained slowly over time to deeper layers. The new denser waters also altered the zonal dynamic height gradient reversing the southward regional flow and enhancing the access of saltier southern waters to higher latitudes. Then, the excess salinity in northern regions favored additional heat injection through deep convection events in later years.
ER –

NR – 104
TY – JOUR
T1 – Periodicities in mean sea-level fluctuations and climate change proxies: Lessons from the modelling for coastal management
AU – Baker, R.G.V.
AU – McGowan, S.A.
JO – Ocean & Coastal Management
VL – 98
SP – 187
EP – 201
PY – 2014
DO – https://doi.org/10.1016/j.ocecoaman.2014.05.027
UR – http://www.sciencedirect.com/science/article/pii/S0964569114001781
AB – The question of whether sea levels and global temperatures are accelerating or decelerating is a major source of current debate. Single taper and multi-taper spectral analysis from seventeen globally distributed tidal stations and twenty climate proxies show aggregate significant common periodicities in mean sea level fluctuations and the climate proxies of approximately 7 yr, 13 yr, 23 yr, 32 yr, 41 yr, 53 yr, 66 yr, 88 yr, 105 yr and 132 yr, respectively. These periods are shown to strongly correlate with an harmonic sequence of n, m = n + n/4 and p = n + n/2n for n = 5.5 yr and this synchronicity allows for a climate state function to be defined by Lotka–Volterra limit cycles. Such a model can include both anthropogenic warming and complex natural cycles, based on past evidence, and these cycles can form or bifurcate into extreme events close to critical values. The model suggests that accelerating sea levels can be in-phase, but lag decelerating global temperatures or vice versa, so a ‘pause’ in global warming should not be surprising. Further, the model can simulate the uneven regional effect of climate responses and replicate the chaos apparent in monthly sea-level records. The approach poses ‘a planner’s dilemma’ whereby the likelihood of a present 1 in 100 yr positive extreme event can either be caused by anthropogenic warming within shorter cycles or by a stationary mean in a longer cycle. We simply show that for rising average temperatures in a double period cascading model, there would be a three-fold increase in the likelihood of an equivalent 1 in 100 yr positive extreme event relative to present over a 20 yr period. A consequence to the ‘planner’s dilemma’ is the ‘manager’s risk imperative’ where risk cycles can be quantified into strategic GIS maps of potential future inundations: identifying vulnerability, defining possible economic impacts and underpinning response strategies that are legally defensible and transparent to a range of stakeholders.
ER –

NR – 105
TY – JOUR
AU – Morrison, Kyle W.
AU – Battley, Phil F.
AU – Sagar, Paul M.
AU – Thompson, David R.
PY – 2015
TI – Population dynamics of Eastern Rockhopper Penguins on Campbell Island in relation to sea surface temperature 1942–2012: current warming hiatus pauses a long-term decline
JO – Polar Biology
SP – 163
EP – 177
VL – 38
IS – 2
AB – Major population changes of marine mega-fauna are ongoing as global warming, and other anthropogenic drivers affect prey availability. The historical stronghold of the Eastern Rockhopper Penguin (Eudyptes chrysocome filholi) was New Zealand’s sub-Antarctic Campbell Island, but the population declined by 94 % between 1942 and 1984. The apparent mechanism of collapse was warm ocean temperatures causing an inadequate food supply. Eudyptes penguin population declines are ongoing at some breeding sites, highlighting the need to investigate the population trend on Campbell Island since 1984. We estimated the Eastern Rockhopper Penguin breeding population size through physical and photo-counts of birds and nests in 2012, and changes in colony area relative to 1984 and 1996 photographs. We estimated the 2012 population size at 33,239 breeding pairs, a 21.8 % decrease from an (adjusted) estimate of 42,528 pairs in 1984. Although substantial, the recent 1984–2012 decline occurred at a much slower rate (? = 0.991) than the 1942–1984 decline (? = 0.940). Despite great variation in trends between colonies ostensibly linked to differences in predation rates, the recent decline occurred primarily between 1984 and 1996, and thereafter the overall population grew. A 100-year time series of extended reconstructed sea surface temperatures (ERSST) confirmed that the population declined during warm periods and increased during cool periods, but that the initial decline began before increases in regional ERSST. Population growth after 1996 appears related to the current global warming hiatus, lower ERSST, and increased abundance of a key prey species. We predict a continuation of the long-term population decline after warming resumes.
UR – https://doi.org/10.1007/s00300-014-1575-x
DO – 10.1007/s00300-014-1575-x
ER –

NR – 106
TY – JOUR
AU – An, Wenling
AU – Hou, Shugui
AU – Zhang, Wangbin
AU – Wu, Shuangye
AU – Xu, Hao
AU – Pang, Hongxi
AU – Wang, Yetang
AU – Liu, Yaping
T1 – Possible recent warming hiatus on the northwestern Tibetan Plateau derived from ice core records
PY – 2016
AB – Many studies have reported enhanced warming trend on the Tibetan Plateau (TP), even during the warming hiatus period. However, most of these studies are based on instrumental data largely collected from the eastern TP, whereas the temperature trend over the extensive northwestern TP remains uncertain due to few meteorological stations. Here we combined the stable isotopic d(18)O record of an ice core recovered in 2012 from the Chongce glacier with the d(18)O records of two other ice cores (i.e., Muztagata and Zangser Kangri) in the same region to establish a regional temperature series for the northwestern TP. The reconstruction shows a significant warming trend with a rate of 0.74?±?0.12?°C/decade for the period 1970–2000, but a decreasing trend from 2001 to 2012. This is consistent with the reduction of warming rates during the recent decade observed at the only two meteorological stations on the northwestern TP, even though most stations on the eastern TP have shown persistent warming during the same period. Our results suggest a possible recent warming hiatus on the northwestern TP. This could have contributed to the relatively stable status of glaciers in this region.
SP – 32813
VL – 6
DO – 10.1038/srep32813
UR – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5017263/
JF – Scientific Reports
ER –

NR – 107
TY – JOUR
T1 – Present contributions to sea level rise by thermal expansion and ice melting and implication on coastal management
AU – Parker, Albert
JO – Ocean & Coastal Management
VL – 98
SP – 202
EP – 211
PY – 2014
DO – https://doi.org/10.1016/j.ocecoaman.2014.05.026
UR – http://www.sciencedirect.com/science/article/pii/S0964569114001744
AB – Increasing ocean heat content has been suggested on the basis of theories. Reconstructions (modelling results based on selected scattered measurements) and simulations (modelling results not based on observations) have both shown a significant warming since the year 1970 that increased at an ever faster rate over the 14 years this century. It is shown here that, contrary to this claim, the detailed measurements of the ocean temperature and salinity by the sampling buoys of the ARGO project show only minor changes of temperature and salinity since the early 2000s. The ARGO results cover the ocean layers 0–2000m except for the North and South Poles. The satellite NSSTC surface air temperature measurements over the world oceans show a global cooling over the last 11 years, and the satellite NSDIC sea ice extent measurements show globally increasing ice coverage over the North and South Poles. The North Pole sea ice is certainly reducing, but over the last 11 years the growth of the South Pole sea ice has more than compensated that loss. The true measurements are in marked contrast to theoretical reconstructions and simulations. This result has a huge implication on coastal management that should be based on observationally derived forecasts rather than “projections” of models lacking validation.
ER –

NR – 108
TY – JOUR
T1 – Recent hiatus caused by decadal shift in Indo-Pacific heating
JF – Science
SP – 532
LP – 535
DO – 10.1126/science.aaa4521
VL – 349
IS – 6247
AU – Nieves, Veronica
AU – Willis, Josh K.
AU – Patzert, William C.
UR – http://science.sciencemag.org/content/349/6247/532.abstract
AB – Global warming apparently slowed, or even stopped, during the first decade of the 21st century. This pause is commonly called the “hiatus.” We know, however, that Earth's climate system is accumulating excess solar energy owing to the build-up of greenhouse gases in the atmosphere. Where, then, has this energy gone if not into the air? Nieves et al. find that over this period, the surface Pacific Ocean has cooled but the upper Indian and Southern Oceans have warmed. Thus, the decade-long hiatus that began in 2003 would appear to be the result of a redistribution of heat within the ocean, rather than a change in the whole-Earth warming rate.Science, this issue p. 532Recent modeling studies have proposed different scenarios to explain the slowdown in surface temperature warming in the most recent decade. Some of these studies seem to support the idea of internal variability and/or rearrangement of heat between the surface and the ocean interior. Others suggest that radiative forcing might also play a role. Our examination of observational data over the past two decades shows some significant differences when compared to model results from reanalyses and provides the most definitive explanation of how the heat was redistributed. We find that cooling in the top 100-meter layer of the Pacific Ocean was mainly compensated for by warming in the 100- to 300-meter layer of the Indian and Pacific Oceans in the past decade since 2003.
ER –

NR – 109
TY – JOUR
AU – Gonzalez-Hidalgo, José Carlos
AU – Peña-Angulo, Dhais
AU – Brunetti, Michele
AU – Cortesi, Nicola
TI – Recent trend in temperature evolution in Spanish mainland (1951–2010): from warming to hiatus
JO – International Journal of Climatology
VL – 36
IS – 6
UR – http://dx.doi.org/10.1002/joc.4519
DO – 10.1002/joc.4519
SP – 2405
EP – 2416
PY – 2016
AB – The most recent debate on global warming focuses on the hiatus in global temperature, for which several explanations have been proposed. On the other hand, spatial variability and nonlinearity in temperature evolution has been recognized as a key point in global change analyses. In this study, we analyse the evolution of the warming rate in the Spanish mainland using the MOTEDAS data set for the last 60 years (1951–2010). Our special emphasis is on the last decades to detect and identify a possible hiatus, and to determine the effects of daytime (Tmax) and night-time (Tmin) records at annual and seasonal scale on the hiatus. Moving windows running trend analyses were applied to calculate temperature trend and significance for any temporal window from the beginning to the end of the series, ranging from 20 years to the whole series length (60 years) The results suggest that the warming rate in the Spanish mainland reached a maximum between 1970 and 1990, followed by a decrease in intensity in both Tmax and Tmin until the present. Furthermore, the decrease in the warming rate in Tmax has been higher than in Tmin for the last three decades; therefore, recent annual warming rates appears to depend more on Tmin than on Tmax. Significant trends disappear from the middle of the 1980s at any temporal window length in both Tmax and Tmin at annual and seasonal scales except in spring Tmin. Some differences among seasons are evident and, during the last few decades, the highest rates of warming are found in spring and summer, with Tmax and Tmin behaving in different ways. This study highlights how the warming rate is highly dependent on the length of the period analysed.
ER –

NR – 110
TY – JOUR
AU – Zhang, Yuanjie
AU – Gao, Zhiqiu
AU – Pan, Zaitao
AU – Li, Dan
AU – Wan, Bingcheng
TI – Record-breaking temperatures in China during the warming and recent hiatus periods
JO – Journal of Geophysical Research: Atmospheres
VL – 121
IS – 1
UR – http://dx.doi.org/10.1002/2015JD023886
DO – 10.1002/2015JD023886
SP – 241
EP – 258
PY – 2016
AB – The observed and modeled record-breaking temperature (RBT) frequency in China is analyzed for different segments of the period 1961–2050 including the hiatus period. It is found that significant changes in the RBT frequency occurred earlier, with greater amplitude, for daily minimum temperatures (TN) compared to maximum temperatures (TX) during the past five decades. Changes in the RBT frequency can be mostly explained by the mean warming trend, especially for TN, while in summer also slightly by variance. Moreover, mean climate change affects more the multiday mean RBT than the single-day counterpart as RBT occurrence is inversely proportional to variance that is smaller for multiday means. In the hiatus period (1998–2013), the ratios of record highs to lows in summer continue to increase in southern China primarily due to the lower frequency of record lows, since the decreasing temperature variance suppressed the increase in record highs under the summer warming. While the winter ratios decreased significantly across most of the country due to the winter cooling. Model simulations show a much smaller asymmetry of the RBT frequency between TX and TN as compared to the observations. The 28-model median overestimates the ratios for TX owning to missing the relative cooling in the “warming hole” region and is unable to reproduce the RBT characteristics in the hiatus period. Under a high-emission scenario, increasing rates of future temperature extremes are projected to accelerate with almost doubling ratio trends in the first half of 21st century compared to the historical results.
ER –

NR – 111
TY – JOUR
T1 – Revisiting the Relationship between Observed Warming and Surface Pressure in the Tibetan Plateau
AU – You, Qinglong
AU – Jiang, Zhihong
AU – Moore, G. W. K.
AU – Bao, Yuntao
AU – Kong, Lei
AU – Kang, Shichang
PY – 2016
DO – 10.1175/JCLI-D-15-0834.1
JF – Journal of Climate
SP – 1721
EP – 1737
VL – 30
IS – 5
AB – The Tibetan Plateau (TP) has an average elevation of over 4000 m and with its surrounding mountains is regarded as Earth?s ?third pole.? As a result of its size and height, climate change in the TP has its own unique characteristics that include a proposed positive correlation between the surface temperature and pressure. This study examines the trends and relationships between the surface pressure and temperature in the TP through the examination of monthly mean data from 71 stations during 1961?2013. On annual, seasonal, and monthly time scales, the TP exhibits a statistically significant warming trend that attains a rate of 0.30°C decade?1 for annual means over the period 1961?2013. The most pronounced warming occurs in winter, in agreement with previous studies, with evidence of acceleration in the rate after the mid-1980s and the global warming slowdown period. For the entire period of 1961?2013, the surface pressure in the TP has a positive trend of 0.08 hPa decade?1 on an annual basis, again with the largest trends occurring in winter. However, unlike what occurred with the surface temperature, the trend in surface pressure, in most cases, reversed sign after the mid-1980s. The trend in the geopotential height at 500 hPa from the National Centers for Environmental Prediction?National Center for Atmospheric Research (NCEP?NCAR) reanalysis is consistent with the observed surface pressure trends. Over the period 1961?2013, there is a seasonal shift in the nature of the relationship between the surface temperature and pressure with a negative correlation during summer and autumn, and a positive correlation during winter. This suggests that the nature of the relationship between these two climate elements reflects the changing nature of the seasonal snow cover (land surface property) and cloud in the region.
UR – https://doi.org/10.1175/JCLI-D-15-0834.1
ER –

NR – 112
TY – JOUR
T1 – Revisiting Whether Recent Surface Temperature Trends Agree with the CMIP5 Ensemble
AU – Lin, Marena
AU – Huybers, Peter
PY – 2016
DO – 10.1175/JCLI-D-16-0123.1
JF – Journal of Climate
SP – 8673
EP – 8687
VL – 29
IS – 24
AB – In an earlier study, a weaker trend in global mean temperature over the past 15 years relative to the preceding decades was characterized as significantly lower than those contained within the phase 5 of the Coupled Model Intercomparison Project (CMIP5) ensemble. In this study, divergence between model simulations and observations is estimated using a fixed-intercept linear trend with a slope estimator that has one-third the noise variance compared to simple linear regression. Following the approach of the earlier study, where intermodel spread is used to assess the distribution of trends, but using the fixed-intercept trend metric demonstrates that recently observed trends in global mean temperature are consistent with the CMIP5 ensemble for all 15-yr intervals of observation?model divergence since 1970. Significant clustering of global trends according to modeling center indicates that the spread in CMIP5 trends is better characterized using ensemble members drawn across models as opposed to using ensemble members from a single model. Despite model?observation consistency at the global level, substantial regional discrepancies in surface temperature trends remain.
UR – https://doi.org/10.1175/JCLI-D-16-0123.1
ER –

NR – 113
TY – JOUR
T1 – Role of Changes in Mean Temperatures versus Temperature Gradients in the Recent Widening of the Hadley Circulation
AU – Adam, Ori
AU – Schneider, Tapio
AU – Harnik, Nili
PY – 2014
DO – 10.1175/JCLI-D-14-00140.1
JF – Journal of Climate
SP – 7450
EP – 7461
VL – 27
IS – 19
AB – The Hadley circulation (HC) has widened in recent decades, and it widens as the climate warms in simulations. But the mechanisms responsible for the widening remain unclear, and the widening in simulations is generally smaller than observed.To identify mechanisms responsible for the HC widening and for model?observation discrepancies, this study analyzes how interannual variations of tropical-mean temperatures and meridional temperature gradients influence the HC width. Changes in mean temperatures are part of any global warming signal, whereas changes in temperature gradients are primarily associated with ENSO. Within this study, 6 reanalysis datasets, 22 Atmospheric Modeling Intercomparison Project (AMIP) simulations, and 11 historical simulations from phase 5 of the Climate Modeling Intercomparison Project (CMIP5) are analyzed, covering the years 1979?2012. It is found that the HC widens as mean temperatures increase or as temperature gradients weaken in most reanalyses and climate models. On average, climate models exhibit a smaller sensitivity of HC width to changes in mean temperatures and temperature gradients than do reanalyses. However, the sensitivities differ substantially among reanalyses, rendering the HC response to mean temperatures in climate models not statistically different from that in reanalyses.While global-mean temperatures did not increase substantially between 1997 and 2012, the HC continued to widen in most reanalyses. The analysis here suggests that the HC widening from 1979 to 1997 is primarily the result of global warming, whereas the widening of the HC from 1997 to 2012 is associated with increased midlatitude temperatures and hence reduced temperature gradients during this period.
UR – https://doi.org/10.1175/JCLI-D-14-00140.1
ER –

NR – 114
TY – JOUR
AU – Wei, Meng
AU – Qiao, FangLi
PY – 2017
TI – Attribution analysis for the failure of CMIP5 climate models to simulate the recent global warming hiatus
JO – Science China Earth Sciences
SP – 397
EP – 408
VL – 60
IS – 2
AB – The Coupled Model Inter-comparison Project Phase 5 (CMIP5) contains a group of state-of-the-art climate models and represents the highest level of climate simulation thus far. However, these models significantly overestimated global mean surface temperature (GMST) during 2006–2014. Based on the ensemble empirical mode decomposition (EEMD) method, the long term change of the observed GMST time series of HadCRUT4 records during 1850–2014 was analyzed, then the simulated GMST by 33 CMIP5 climate models was assessed. The possible reason that climate models failed to project the recent global warming hiatus was revealed. Results show that during 1850–2014 the GMST on a centennial timescale rose with fluctuation, dominated by the secular trend and the multi-decadal variability (MDV). The secular trend was relatively steady beginning in the early 20th century, with an average warming rate of 0.0883°C/decade over the last 50 years. While the MDV (with a ~65-year cycle) showed 2.5 multi-decadal waves during 1850–2014, which deepened and steepened with time, the alarming warming over the last quarter of the 20th century was a result of the concurrence of the secular warming trend and the warming phase of the MDV, both of which accounted one third of the temperature increase during 1975–1998. Recently the slowdown of global warming emerged as the MDV approached its third peak, leading to a reduction in the warming rate. A comparative analysis between the GMST time series derived from HadCRUT4 records and 33 CMIP5 model outputs reveals that the GMSTs during the historical simulation period of 1850–2005 can be reproduced well by models, especially on the accelerated global warming over the last quarter of 20th century. However, the projected GMSTs and their linear trends during 2006–2014 under the RCP4.5 scenario were significantly higher than observed. This is because the CMIP5 models confused the MDV with secular trend underlying the GMST time series, which results in a fast secular trend and an improper MDV with irregular phases and small amplitudes. This implies that the role of atmospheric CO2 in global warming may be overestimated, while the MDV which is an interior oscillation of the climate system may be underestimated, which should be related to insufficient understanding of key climatic internal dynamic processes. Our study puts forward an important criterion for the new generation of climate models: they should be able to simulate both the secular trend and the MDV of GMST.
UR – https://doi.org/10.1007/s11430-015-5465-y
DO – 10.1007/s11430-015-5465-y
ER –

NR – 115
TY – JOUR
AU – Zhou, Chunlüe
AU – Wang, Kaicun
T1 – Coldest Temperature Extreme Monotonically Increased and Hottest Extreme Oscillated over Northern Hemisphere Land during Last 114 Years
PY – 2016
AB – Most studies on global warming rely on global mean surface temperature, whose change is jointly determined by anthropogenic greenhouse gases (GHGs) and natural variability. This introduces a heated debate on whether there is a recent warming hiatus and what caused the hiatus. Here, we presented a novel method and applied it to a 5°?×?5° grid of Northern Hemisphere land for the period 1900 to 2013. Our results show that the coldest 5% of minimum temperature anomalies (the coldest deviation) have increased monotonically by 0.22?°C/decade, which reflects well the elevated anthropogenic GHG effect. The warmest 5% of maximum temperature anomalies (the warmest deviation), however, display a significant oscillation following the Atlantic Multidecadal Oscillation (AMO), with a warming rate of 0.07?°C/decade from 1900 to 2013. The warmest (0.34?°C/decade) and coldest deviations (0.25? °C/decade) increased at much higher rates over the most recent decade than last century mean values, indicating the hiatus should not be interpreted as a general slowing of climate change. The significant oscillation of the warmest deviation provides an extension of previous study reporting no pause in the hottest temperature extremes since 1979, and first uncovers its increase from 1900 to 1939 and decrease from 1940 to 1969.
SP – 25721
VL – 6
DO – 10.1038/srep25721
UR – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4865736/
JF – Scientific Reports
ER –

NR – 116
TY – JOUR
AU – Dai, Aiguo
AU – Fyfe, John C.
AU – Xie, Shang-Ping
AU – Dai, Xingang
TI – Decadal modulation of global surface temperature by internal climate variability
JF – Nature Climate Change
PY – 2015
VL – 5
SP – 555
UR – http://dx.doi.org/10.1038/nclimate2605
DO – 10.1038/nclimate2605
AB – Despite a steady increase in atmospheric greenhouse gases (GHGs), global-mean surface temperature (T) has shown no discernible warming since about 2000, in sharp contrast to model simulations, which on average project strong warming1,2,3. The recent slowdown in observed surface warming has been attributed to decadal cooling in the tropical Pacific1,4,5, intensifying trade winds5, changes in El Niño activity6,7, increasing volcanic activity8,9,10 and decreasing solar irradiance7. Earlier periods of arrested warming have been observed but received much less attention than the recent period, and their causes are poorly understood. Here we analyse observed and model-simulated global T fields to quantify the contributions of internal climate variability (ICV) to decadal changes in global-mean T since 1920. We show that the Interdecadal Pacific Oscillation (IPO) has been associated with large T anomalies over both ocean and land. Combined with another leading mode of ICV, the IPO explains most of the difference between observed and model-simulated rates of decadal change in global-mean T since 1920, and particularly over the so-called ‘hiatus’ period since about 2000. We conclude that ICV, mainly through the IPO, was largely responsible for the recent slowdown, as well as for earlier slowdowns and accelerations in global-mean T since 1920, with preferred spatial patterns different from those associated with GHG-induced warming or aerosol-induced cooling. Recent history suggests that the IPO could reverse course and lead to accelerated global warming in the coming decades.
ER –

NR – 117
TY – JOUR
AU – Lin, Yong
AU – Franzke, Christian L. E.
TI – Scale-dependency of the global mean surface temperature trend and its implication for the recent hiatus of global warming
JF – Scientific Reports
PY – 2015
VL – 5
SP – 12971
UR – http://dx.doi.org/10.1038/srep12971
DO – 10.1038/srep12971
AB – Studies of the global mean surface temperature trend are typically conducted at a single (usually annual or decadal) time scale. The used scale does not necessarily correspond to the intrinsic scales of the natural temperature variability. This scale mismatch complicates the separation of externally forced temperature trends from natural temperature fluctuations. The hiatus of global warming since 1999 has been claimed to show that human activities play only a minor role in global warming. Most likely this claim is wrong due to the inadequate consideration of the scale-dependency in the global surface temperature (GST) evolution. Here we show that the variability and trend of the global mean surface temperature anomalies (GSTA) from January 1850 to December 2013, which incorporate both land and sea surface data, is scale-dependent and that the recent hiatus of global warming is mainly related to natural long-term oscillations. These results provide a possible explanation of the recent hiatus of global warming and suggest that the hiatus is only temporary.
ER –

NR – 118
TY – JOUR
T1 – Does the NMME Capture a Recent Decadal Shift toward Increasing Drought Occurrence in the Southwestern United States?
AU – Barnston, Anthony G.
AU – Lyon, Bradfield
PY – 2015
DO – 10.1175/JCLI-D-15-0311.1
JF – Journal of Climate
SP – 561
EP – 581
VL – 29
IS – 2
AB – A global-scale decadal climate shift, beginning in 1998/99 and enduring through 2013, has been documented in recent studies, with associated precipitation shifts in key regions throughout the world. These precipitation shifts are most easily detected during March?May when ENSO effects are weak. Analyses have linked this climate shift to a shift in the Pacific decadal variability (PDV) pattern to its negative phase. Here the authors evaluate the predictive skill of the North American Multimodel Ensemble (NMME), and the CFSv2 model alone, in maintaining the observed precipitation shifts in seasonal forecasts, emphasizing the southwestern United States where deficient precipitation has tended to prevail since the late 1990s.The NMME hindcasts out to 6 months lead are found to maintain the observed decadal precipitation shifts in key locations qualitatively correctly, but with increasingly underestimated amplitude with increasing lead time. This finding holds in the separate CFSv2 model hindcasts. The decadal precipitation shift is relatively well reproduced in the southwestern United States. The general underestimation of the precipitation shift is suggested to be related to a muted reproduction of the observed shift in Pacific sea surface temperature (SST). This conclusion is supported by runs from a different (but overlapping) set of atmospheric models, which when forced with observed SST reproduce the decadal shifts quite well. Overall, the capability of the NMME model hindcasts to reflect the observed decadal rainfall pattern shift, but with weakened amplitude (especially at longer leads), underscores the broader challenge of retaining decadal signals in predictions of droughts and pluvials at seasonal-to-interannual time scales.
UR – https://doi.org/10.1175/JCLI-D-15-0311.1
ER –

NR – 119
TY – JOUR
AU – Knutson, Thomas R.
AU – Ploshay, Jeffrey J.
PY – 2016
TI – Detection of anthropogenic influence on a summertime heat stress index
JO – Climatic Change
SP – 25
EP – 39
VL – 138
IS – 1
AB – One of the most consequential impacts of anthropogenic warming on humans may be increased heat stress, combining temperature and humidity effects. Here we examine whether there are now detectable changes in summertime heat stress over land regions. As a heat stress metric we use a simplified wet bulb globe temperature (WBGT) index. Observed trends in WBGT (1973–2012) are compared to trends from CMIP5 historical simulations (eight-model ensemble) using either anthropogenic and natural forcing agents combined or natural forcings alone. Our analysis suggests that there has been a detectable anthropogenic increase in mean summertime heat stress since 1973, both globally and in most land regions analyzed. A detectable increase is found over a larger fraction of land for WBGT than for temperature, as WBGT summertime means have lower interannual variability than surface temperature at gridbox scales. Notably, summertime WBGT over land has continued increasing in recent years–consistent with climate models–despite the apparent ‘hiatus’ in global warming and despite a decreasing tendency in observed relative humidity over land since the late 1990s.
UR – https://doi.org/10.1007/s10584-016-1708-z
DO – 10.1007/s10584-016-1708-z
ER –

NR – 120
TY – JOUR
AU – Dong, Lu
AU – Zhou, Tianjun
AU – Dai, Aiguo
AU – Song, Fengfei
AU – Wu, Bo
AU – Chen, Xiaolong
TI – The Footprint of the Inter-decadal Pacific Oscillation in Indian Ocean Sea Surface Temperatures
JO – Scientific Reports
PY – 2016
VL – 6
SP – 21251
UR – http://dx.doi.org/10.1038/srep21251
DO – 10.1038/srep21251
AB – Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871–2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcings account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. The decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.
ER –

NR – 121
TY – JOUR
AU – Blanchette, Jeanne
AU – Huang, Yi
TI – Earth Infrared Radiation Spectra During Global Warming Hiatus
JO – McGill Science Undergraduate Research Journal
PY – 2015
VL – 10
IS – 1
SP – 14
EP – 17
UR – http://msurj.mcgill.ca/vol10/iss1/MSURJ2015.pdf#page=14
AB – Background: Since 1997-98, observations of annual mean surface temperature have shown a slowdown of global temperature increases, suggesting a hiatus in global warming. Given this finding, we are interested in diagnosing trends in the Earth’s outgoing longwave radiation (OLR) spectrum throughout the last decade. Methods: We calculated the trend in OLR measured by the Atmospheric Infrared Sounder (AIRS) aboard NASA’s Aqua satellite between 2003 and 2013, and compared these results with the trend in atmospheric and surface temperature and tropospheric absolute humidity, obtained from AIRS retrieval product and from the ECMWF (European Center for Medium range Weather Forecasting) Re-Analysis (ERA) interim product. We also isolated the greenhouse effect from the OLR trend by subtracting the amount of surface radiation emitted from the total radiation received by the sounder. Results: The OLR trend is negative in the CO2 absorption band, negative in the window spectral region, and positive in the water vapor band. The trend in surface and tropospheric temperature is negative, as is the trend in tropospheric absolute humidity. The greenhouse effect is increasing in the CO2 band, generally slightly increasing in the window region, and decreasing in the H2O band. Conclusion: Our results show that the CO2 forcing was still present globally through the last decade, with steadily increasing effects. Contributors to the negative trend in OLR in the window region are a small decrease in surface temperature and a strong decrease in tropospheric temperature, where tropospheric H2O emit radiation to space. The decreasing effect of water vapor in the H2O band is due to decreasing tropospheric humidity. This analysis will allow us to detect the changes in greenhouse gas forcing, to examine the correlated surface temperature response, and to study changes and effects in tropospheric water vapor concentration.
ER –

NR – 122
TY – JOUR
AU – Zhou, Chunlüe
AU – Wang, Kaicun
TI – Spatiotemporal Divergence of the Warming Hiatus over Land Based on Different Definitions of Mean Temperature
JO – Scientific Reports
PY – 2016
VL – 6
SP – 31789
UR – http://dx.doi.org/10.1038/srep31789
DO – 10.1038/srep31789
AB – Existing studies of the recent warming hiatus over land are primarily based on the average of daily minimum and maximum temperatures (T2). This study compared regional warming rates of mean temperature based on T2 and T24 calculated from hourly observations available from 1998 to 2013. Both T2 and T24 show that the warming hiatus over land is apparent in the mid-latitudes of North America and Eurasia, especially in cold seasons, which is closely associated with the negative North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) and cold air propagation by the Arctic-original northerly wind anomaly into mid-latitudes. However, the warming rates of T2 and T24 are significantly different at regional and seasonal scales because T2 only samples air temperature twice daily and cannot accurately reflect land-atmosphere and incoming radiation variations in the temperature diurnal cycle. The trend has a standard deviation of 0.43?°C/decade for T2 and 0.41?°C/decade for T24, and 0.38?°C/decade for their trend difference in 5°?×?5° grids. The use of T2 amplifies the regional contrasts of the warming rate, i.e., the trend underestimation in the US and overestimation at high latitudes by T2.
ER –

NR – 123
TY – JOUR
AU – Urabe, Yusuke
AU – Maeda, Shuhei
TI – The Relationship between Japans Recent Temperature and Decadal Variability
JO – SOLA
PY – 2014
DA – 2014
VL – 10
SP – 176-179
UR – https://ci.nii.ac.jp/naid/130004704543/en/
DO – 10.2151/sola.2014-037
AB – Since the late 1990s, surface temperature has been higher than (near or lower than) normal for summer/autumn (winter/spring) over Japan, indicating that the seasonal temperature contrast has become enhanced. In order to relate this to global-scale variability on decadal timescale, atmospheric re-analysis and ocean assimilation datasets were analyzed. It is suggested that the La Niña-like conditions which have been frequently observed in the tropical Pacific oceanic and atmospheric fields in the last decade have contributed to these temperature tendencies observed in Japan. These global characteristics are consistent with the global warming hiatus. The results presented here indicate that not only interannual variability and century-scale long-term trends but also decadal variability in global oceanic and atmospheric fields significantly affect Japans temperature.
ER –

NR – 124
TY – JOUR
AU – He, Haozhe
AU – Yang, Jing
AU – Wu, Liguang
AU – Gong, Daoyi
AU – Wang, Bin
AU – Gao, Miaoni
PY – 2017
TI – Unusual growth in intense typhoon occurrences over the Philippine Sea in September after the mid-2000s
JO – Climate Dynamics
SP – 1893
EP – 1910
VL – 48
IS – 5
AB – During the global warming hiatus period (1998–present), a pronounced increase in the number of intense typhoon occurrences was identified over the Philippine Sea (PS: 5°–25°N, 125°–140°E) in September after the mid-2000s. Comparing two periods before and after the mid-2000s indicates that intense typhoons rarely occurred over the PS in September before the mid-2000s, with a frequency of fewer than 0.4 per year, but reached up to nearly 1.5 per year after the mid-2000s. The abrupt increase in intense typhoon occurrences over the PS was primarily attributed to increased tropical cyclone (TC) genesis and favorable large-scale conditions for TC intensification. The increase in TC genesis number over the PS was caused by contributory dynamical conditions, including positive low-level relative vorticity anomalies and anomalous ascents, which corresponded to a southwestward shift and strengthening of the monsoon trough. In addition, among the favorable large-scale conditions, the increased relative humidity that resulted from intensified moisture flux convergence exerted essential effect on the TC intensification. These changes in atmospheric environmental conditions favoring intense typhoon occurrences over the PS were primarily associated with the change in the tropical Indo-Pacific sea surface temperature (SST) around the mid-2000s. Besides that, the positive feedback TCs exerted on the circulation was also conducive to the unusual growth in intense typhoon occurrences over the PS. And note that the role of SST anomalies in the air–sea interaction is the key to interpret why the unique phenomenon only occurred in September.
UR – https://doi.org/10.1007/s00382-016-3181-9
DO – 10.1007/s00382-016-3181-9
ER –

NR – 125
TY – JOUR
AU – Lovejoy, S.
TI – Using scaling for macroweather forecasting including the pause
JO – Geophysical Research Letters
VL – 42
IS – 17
UR – http://dx.doi.org/10.1002/2015GL065665
DO – 10.1002/2015GL065665
SP – 7148
EP – 7155
PY – 2015
AB – The ScaLIng Macroweather model (SLIMM) is a new class of stochastic atmospheric model. It exploits the large system memory to overcome the biases of conventional numerical climate models, it makes hindcasts and forecasts over macroweather forecast horizons (˜10?days to decades). Using the simplest (scalar), SLIMM model with only two parameters, we present various twentieth century hindcasts including several of the slowdown (“pause”) in the warming since 1998. The 1999–2013 hindcast is accurate to within ±0.11?K, with all the 2002–2013 anomalies hindcast to within ±0.02?K. In comparison, the Climate Model Intercomparison Project Phase 3 hindcasts were on average about 0.2?K too warm.
ER –

NR – 126
TY – JOUR
AU – Guan, Xiaodan
AU – Huang, Jianping
AU – Guo, Ruixia
AU – Lin, Pu
TI – The role of dynamically induced variability in the recent warming trend slowdown over the Northern Hemisphere
JO – Scientific Reports
PY – 2015
VL – 5
SP – 12669
UR – http://dx.doi.org/10.1038/srep12669
DO – 10.1038/srep12669
AB – Since the slowing of the trend of increasing surface air temperature (SAT) in the late 1990?s, intense interest and debate have arisen concerning the contribution of human activities to the warming observed in previous decades. Although several explanations have been proposed for the warming-trend slowdown (WTS), none has been generally accepted. We investigate the WTS using a recently developed methodology that can successfully identify and separate the dynamically induced and radiatively forced SAT changes from raw SAT data. The dynamically induced SAT changes exhibited an obvious cooling effect relative to the warming effect of the adjusted SAT in the hiatus process. A correlation analysis suggests that the changes are dominated primarily by the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). Our results confirm that dynamically induced variability caused the WTS. The radiatively forced SAT changes are determined mainly by anthropogenic forcing, indicating the warming influence of greenhouse gases (GHGs), which reached levels of 400?ppm during the hiatus period. Therefore, the global SAT will not remain permanently neutral. The increased radiatively forced SAT will be amplified by increased dynamically induced SAT when the natural mode returns to a warming phase in the next period.
ER –

NR – 127
TY – JOUR
AU – Pasini, Antonello
AU – Triacca, Umberto
AU – Attanasio, Alessandro
PY – 2017
TI – Evidence for the role of the Atlantic multidecadal oscillation and the ocean heat uptake in hiatus prediction
JO – Theoretical and Applied Climatology
SP – 873
EP – 880
VL – 129
IS – 3
AB – The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean–atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001–2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere–ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean.
UR – https://doi.org/10.1007/s00704-016-1818-6
DO – 10.1007/s00704-016-1818-6
ER –

NR – 128
TY – JOUR
T1 – Extreme North America Winter Storm Season of 2013/14: Roles of Radiative Forcing and the Global Warming Hiatus
AU – Yang, Xiaosong
AU – Vecchi, G. A.
AU – Delworth, T. L.
AU – Paffendorf, K.
AU – Jia, L.
AU – Gudgel, R.
AU – Zeng, F.
AU – Underwood, Seth D.
PY – 2015
DO – 10.1175/BAMS-D-15-00133.1
JF – Bulletin of the American Meteorological Society
SP – S25
EP – S28
VL – 96
IS – 12
UR – https://doi.org/10.1175/BAMS-D-15-00133.1
AB – The extreme 2013/14 winter storm season over much of North America was made more likely by the multiyear anomalous tropical Pacific winds associated with the recent global warming hiatus.
ER –

NR – 129
TY – JOUR
AU – Huang, Rui Xin
PY – 2015
TI – Heaving modes in the world oceans
JO – Climate Dynamics
SP – 3563
EP – 3591
VL – 45
IS – 11
AB – Part of climate changes on decadal time scales can be interpreted as the result of adiabatic motions associated with the adjustment of wind-driven circulation, i.e., the heaving of the isopycnal surfaces. Heat content changes in the ocean, including hiatus of global surface temperature and other phenomena, can be interpreted in terms of heaving associated with adjustment of wind-driven circulation induced by decadal variability of wind. A simple reduced gravity model is used to examine the consequence of adiabatic adjustment of the wind-driven circulation. Decadal changes in wind stress forcing can induce three-dimensional redistribution of warm water in the upper ocean. In particular, wind stress change can generate baroclinic modes of heat content anomaly in the vertical direction; in fact, changes in stratification observed in the ocean may be induced by wind stress change at local or in the remote parts of the world oceans. Intensification of the equatorial easterly can induce cooling in the upper layer and warming in the subsurface layer. The combination of this kind of heat content anomaly with the general trend of warming of the whole water column under the increasing greenhouse effect may offer an explanation for the hiatus of global surface temperature and the accelerating subsurface warming over the past 10–15 years. Furthermore, the meridional transport of warm water in the upper ocean can lead to sizeable transient meridional overturning circulation, poleward heat flux and vertical heat flux. Thus, heaving plays a key role in the oceanic circulation and climate.
UR – https://doi.org/10.1007/s00382-015-2557-6
DO – 10.1007/s00382-015-2557-6
ER –

NR – 130
TY – JOUR
AU – Zhou, Chen
AU – Zelinka, Mark D.
AU – Klein, Stephen A.
TI – Impact of decadal cloud variations on the Earth’s energy budget
JO – Nature Geoscience
PY – 2016
VL – 9
SP – 871
UR – http://dx.doi.org/10.1038/ngeo2828
DO – 10.1038/ngeo2828
AB – Feedbacks of clouds on climate change strongly influence the magnitude of global warming1,2,3. Cloud feedbacks, in turn, depend on the spatial patterns of surface warming4,5,6,7,8,9, which vary on decadal timescales. Therefore, the magnitude of the decadal cloud feedback could deviate from the long-term cloud feedback4. Here we present climate model simulations to show that the global mean cloud feedback in response to decadal temperature fluctuations varies dramatically due to time variations in the spatial pattern of sea surface temperature. We find that cloud anomalies associated with these patterns significantly modify the Earth’s energy budget. Specifically, the decadal cloud feedback between the 1980s and 2000s is substantially more negative than the long-term cloud feedback. This is a result of cooling in tropical regions where air descends, relative to warming in tropical ascent regions, which strengthens low-level atmospheric stability. Under these conditions, low-level cloud cover and its reflection of solar radiation increase, despite an increase in global mean surface temperature. These results suggest that sea surface temperature pattern-induced low cloud anomalies could have contributed to the period of reduced warming between 1998 and 2013, and offer a physical explanation of why climate sensitivities estimated from recently observed trends are probably biased low4.
ER –

NR – 131
TY – JOUR
AU – Wang, Linying
AU – Yuan, Xing
AU – Xie, Zhenghui
AU – Wu, Peili
AU – Li, Yaohui
TI – Increasing flash droughts over China during the recent global warming hiatus
JO – Scientific Reports
PY – 2016
VL – 6
SP – 30571
UR – http://dx.doi.org/10.1038/srep30571
DO – 10.1038/srep30571
AB – The recent global warming slowdown or hiatus after the big El Niño event in 1997/98 raises the questions of whether terrestrial hydrological cycle is being decelerated and how do the hydrological extremes respond to the hiatus. However, the rapidly developing drought events that are termed as “flash droughts” accompanied by extreme heat, low soil moisture and high evapotranspiration (ET), occurred frequently around the world, and caused devastating impacts on crop yields and water supply. Here, we investigate the long-term trend and variability of flash droughts over China. Flash droughts are most likely to occur over humid and semi-humid regions, such as southern and northeastern China. Flash drought averaged over China increased by 109% from 1979 to 2010, and the increase was mainly due to a long term warming of temperature (50%), followed by the contributions from decreasing soil moisture and increasing ET. There was a slight drop in temperature after 1997, but the increasing trend of flash droughts was tripled. Further results indicate that the decreasing temperature was compensated by the accelerated drying trends of soil moisture and enhanced ET, leading to an acceleration of flash droughts during the warming hiatus. The anthropogenic warming in the next few decades may exacerbate future flash drought conditions in China.
ER –

NR – 132
TY – JOUR
TI – Investigation on the Tendencies of the Land–Ocean Warming Contrast in the Recent Decades
SP – 1522
EP – 1526
AU – L. Zhao
AU – J. Xu
AU – A. Powell
AU – D. Guo
AU – C. Shi
AU – M. Shao
AU – D. Wang
PY – 2016
DO – 10.1109/LGRS.2016.2594954
JO – IEEE Geoscience and Remote Sensing Letters
IS – 10
VL – 13
AB – In this letter, the surface climate temperature trends for the land and the oceans (land-ocean warming contrast) have been examined and compared based on five data sets. The five data sets included three reconstructed data sets of surface temperature observations and two data sets derived using the satellite microwave sounding unit retrieval products in the lower troposphere (LT) for the period from January 1980 to December 2014. Unlike previous studies, the current study shows that the warming trends significantly decreased over both the land and ocean since 1992 and reached their minimum (near zero) in the early 2000s, which is consistent with the occurrence of the warming hiatus. However, due to the sharp decrease in the surface warming trend over the land (1992 to 2007) in conjunction with an increase in the ocean surface warming trend after 2002, the combined trend carries an overall positive sign (between 2005 and 2007) due to the greater ocean warming trend. The rate of warming increase in the ocean, which began in 2002, is surprisingly fast and is approaching the highest warming trends observed over the land since 1980. These basic land and ocean trend results are confirmed by all five data sets with slightly different values due to the various techniques used in compiling the data sets. However, there is consistency in the overall trend pattern results.
ER –

NR – 133
TY – JOUR
AU – Santer, Benjamin D.
AU – Solomon, Susan
AU – Bonfils, Céline
AU – Zelinka, Mark D.
AU – Painter, Jeffrey F.
AU – Beltran, Francisco
AU – Fyfe, John C.
AU – Johannesson, Gardar
AU – Mears, Carl
AU – Ridley, David A.
AU – Vernier, Jean-Paul
AU – Wentz, Frank J.
TI – Observed multivariable signals of late 20th and early 21st century volcanic activity
JO – Geophysical Research Letters
VL – 42
IS – 2
UR – http://dx.doi.org/10.1002/2014GL062366
DO – 10.1002/2014GL062366
SP – 500
EP – 509
PY – 2015
AB – The relatively muted warming of the surface and lower troposphere since 1998 has attracted considerable attention. One contributory factor to this “warming hiatus” is an increase in volcanically induced cooling over the early 21st century. Here we identify the signals of late 20th and early 21st century volcanic activity in multiple observed climate variables. Volcanic signals are statistically discernible in spatial averages of tropical and near-global SST, tropospheric temperature, net clear-sky short-wave radiation, and atmospheric water vapor. Signals of late 20th and early 21st century volcanic eruptions are also detectable in near-global averages of rainfall. In tropical average rainfall, however, only a Pinatubo-caused drying signal is identifiable. Successful volcanic signal detection is critically dependent on removal of variability induced by the El Niño–Southern Oscillation.
ER –

NR – 134
TY – JOUR
AU – Peyser, Cheryl E.
AU – Yin, Jianjun
AU – Landerer, Felix W.
AU – Cole, Julia E.
TI – Pacific sea level rise patterns and global surface temperature variability
JO – Geophysical Research Letters
VL – 43
IS – 16
UR – http://dx.doi.org/10.1002/2016GL069401
DO – 10.1002/2016GL069401
SP – 8662
EP – 8669
PY – 2016
AB – During 1998–2012, climate change and sea level rise (SLR) exhibit two notable features: a slowdown of global surface warming (hiatus) and a rapid SLR in the tropical western Pacific. To quantify their relationship, we analyze the long-term control simulations of 38 climate models. We find a significant and robust correlation between the east-west contrast of dynamic sea level (DSL) in the Pacific and global mean surface temperature (GST) variability on both interannual and decadal time scales. Based on linear regression of the multimodel ensemble mean, the anomalously fast SLR in the western tropical Pacific observed during 1998–2012 indicates suppression of a potential global surface warming of 0.16°?±?0.06°C. In contrast, the Pacific contributed 0.29°?±?0.10°C to the significant interannual GST increase in 1997/1998. The Pacific DSL anomalies observed in 2015 suggest that the strong El Niño in 2015/2016 could lead to a 0.21°?±?0.07°C GST jump.
ER –

NR – 135
TY – JOUR
AU – Chikamoto, Y.
AU – Mochizuki, T.
AU – Timmermann, A.
AU – Kimoto, M.
AU – Watanabe, M.
TI – Potential tropical Atlantic impacts on Pacific decadal climate trends
JO – Geophysical Research Letters
VL – 43
IS – 13
UR – http://dx.doi.org/10.1002/2016GL069544
DO – 10.1002/2016GL069544
SP – 7143
EP – 7151
PY – 2016
AB – The tropical Pacific cooling from the early 1990s to 2013 has contributed to the slowdown of globally averaged sea surface temperatures (SSTs). The origin of this regional cooling trend still remains elusive. Here we demonstrate that the remote impact of Atlantic SST anomalies, as well as local atmosphere-ocean interactions, contributed to the eastern Pacific cooling during this period. By assimilating observed three-dimensional Atlantic temperature and salinity anomalies into a coupled general circulation model, we are able to qualitatively reproduce the observed Pacific decadal trends of SST and sea level pressure (SLP), albeit with reduced amplitude. Although a major part of the Pacific SLP trend can be explained by equatorial Pacific SST forcing only, the origin of this low-frequency variability can be traced back further to the remote impacts of equatorial Atlantic and South Atlantic SST trends. Atlantic SST impacts on the atmospheric circulation can also be detected for the Northeastern Pacific, thus providing a linkage between Atlantic climate and Western North American drought conditions.
ER –

NR – 136
TY – JOUR
AU – Ramesh, Nandini
AU – Cane, Mark A.
AU – Seager, Richard
AU – Lee, Dong Eun
PY – 2017
TI – Predictability and prediction of persistent cool states of the Tropical Pacific Ocean
JO – Climate Dynamics
SP – 2291
EP – 2307
VL – 49
IS – 7
AB – The Tropical Pacific Ocean displays persistently cool sea surface temperature (SST) anomalies that last several years to a decade, with either no El Niño events or a few weak El Niño events. These cause large-scale droughts in the extratropics, including major North American droughts such as the 1930s Dust Bowl, and also modulate the global mean surface temperature. Here we show that two models with different levels of complexity—the Zebiak–Cane intermediate model and the Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1—are able to produce such periods in a realistic manner. We then test the predictability of these periods in the Zebiak–Cane model using an ensemble of experiments with perturbed initial states. Our results show that in most cases the cool mean state is predictable. We then apply this method to make retrospective forecasts of shifts in the decadal mean state and to forecast the mean state of the Tropical Pacific Ocean for the upcoming decade. Our results suggest that the Pacific will undergo a shift to a warmer mean state after the 2015–2016 El Niño. This could imply the cessation of the drier than normal conditions that have generally afflicted southwest North America since the 1997–1998 El Niño, as well as the twenty-first-century pause in global warming. Implications for our understanding of the origins of such persistent cool states and the possibility of improving predictions of large-scale droughts are discussed.
UR – https://doi.org/10.1007/s00382-016-3446-3
DO – 10.1007/s00382-016-3446-3
ER –

NR – 137
TY – JOUR
AU – Knutson, Thomas R.
AU – Zhang, Rong
AU – Horowitz, Larry W.
TI – Prospects for a prolonged slowdown in global warming in the early 21st century
JO – Nature Communications
PY – 2016
VL – 7
SP – 13676
UR – http://dx.doi.org/10.1038/ncomms13676
DO – 10.1038/ncomms13676
AB – Global mean temperature over 1998 to 2015 increased at a slower rate (0.1?K decade-1) compared with the ensemble mean (forced) warming rate projected by Coupled Model Intercomparison Project 5 (CMIP5) models (0.2?K decade-1). Here we investigate the prospects for this slower rate to persist for a decade or more. The slower rate could persist if the transient climate response is overestimated by CMIP5 models by a factor of two, as suggested by recent low-end estimates. Alternatively, using CMIP5 models’ warming rate, the slower rate could still persist due to strong multidecadal internal variability cooling. Combining the CMIP5 ensemble warming rate with internal variability episodes from a single climate model—having the strongest multidecadal variability among CMIP5 models—we estimate that the warming slowdown (<0.1?K decade-1 trend beginning in 1998) could persist, due to internal variability cooling, through 2020, 2025 or 2030 with probabilities 16%, 11% and 6%, respectively.
ER –

NR – 138
TY – JOUR
AU – Gleisner, Hans
AU – Thejll, Peter
AU – Christiansen, Bo
AU – Nielsen, Johannes K.
TI – Recent global warming hiatus dominated by low-latitude temperature trends in surface and troposphere data
JO – Geophysical Research Letters
VL – 42
IS – 2
UR – http://dx.doi.org/10.1002/2014GL062596
DO – 10.1002/2014GL062596
SP – 510
EP – 517
PY – 2015
AB – Over the last 15 years, global mean surface temperatures exhibit only weak trends. Recent studies have attempted to attribute this so called temperature hiatus to several causes, amongst them incomplete sampling of the rapidly warming Arctic region. We here examine zonal mean temperature trends in satellite-based tropospheric data sets (based on data from (Advanced) Microwave Sounding Unit and Global Navigation Satellite System Radio Occultation instruments) and in global surface temperatures (HadCRUT4). Omission of successively larger polar regions from the global mean temperature calculations, in both tropospheric and surface data sets, shows that data gaps at high latitudes cannot explain the observed differences between the hiatus and the prehiatus period. Instead, the dominating causes of the global temperature hiatus are found at low latitudes. The combined use of several independent data sets, representing completely different measurement techniques and sampling characteristics, strengthens the conclusions.
ER –

NR – 139
TY – JOUR
AU – England, Matthew H.
AU – Kajtar, Jules B.
AU – Maher, Nicola
TI – Robust warming projections despite the recent hiatus
JO – Nature Climate Change
PY – 2015
VL – 5
SP – 394
UR – http://dx.doi.org/10.1038/nclimate2575
DO – 10.1038/nclimate2575
AB – The hiatus in warming has led to questions about the reliability of long-term projections, yet here we show they are statistically unchanged when considering only ensemble members that capture the recent hiatus. This demonstrates the robust nature of twenty-first century warming projections.
ER –

NR – 140
TY – JOUR
T1 – Role of Indian Ocean SST variability on the recent global warming hiatus
AU – Arora, Anika
AU – Rao, Suryachandra A.
AU – Chattopadhyay, R.
AU – Goswami, Tanmoy
AU – George, Gibies
AU – Sabeerali, C.T.
JO – Global and Planetary Change
VL – 143
SP – 21
EP – 30
PY – 2016
DO – https://doi.org/10.1016/j.gloplacha.2016.05.009
UR – http://www.sciencedirect.com/science/article/pii/S0921818115300412
AB – Previous studies have shown a slowdown in the warming rate of the annual mean global surface temperature in the recent decade and it is referred to as the hiatus in global warming. Some recent studies have suggested that the hiatus in global warming is possibly due to strong cooling in the tropical Pacific. This study investigates the possible role of the Indian Ocean warming on the tropical Pacific cooling. Despite the continued rise in sea surface temperature (SST) over the tropical Indian Ocean, SST over the tropical Pacific has shown a cooling trend in the recent decade (2002 – 2012). It is well known fact that the Indian Ocean and the Pacific Ocean are strongly coupled to each other and the Indian Ocean basin wide warming is triggered by El Niño on interannual time scale. However, in the recent decade, this relationship is weakening. The recent Indian Ocean warming is triggering a Matsuno-Gill type response in the atmosphere by generating anomalous cyclonic circulations on either side of equator over the tropical Indian Ocean and anomalous easterlies along the tropical Pacific Ocean. These anomalous easterlies result in Ekman divergence in the equatorial Pacific and produce upwelling Kelvin waves, cools the tropical Pacific and therefore indirectly contributes to the hiatus in global warming.
ER –

NR – 141
TY – JOUR
T1 – A Significant Component of Unforced Multidecadal Variability in the Recent Acceleration of Global Warming
AU – DelSole, Timothy
AU – Tippett, Michael K.
AU – Shukla, Jagadish
PY – 2010
DO – 10.1175/2010JCLI3659.1
JF – Journal of Climate
SP – 909
EP – 926
VL – 24
IS – 3
AB – The problem of separating variations due to natural and anthropogenic forcing from those due to unforced internal dynamics during the twentieth century is addressed using state-of-the-art climate simulations and observations. An unforced internal component that varies on multidecadal time scales is identified by a new statistical method that maximizes integral time scale. This component, called the internal multidecadal pattern (IMP), is stochastic and hence does not contribute to trends on long time scales; however, it can contribute significantly to short-term trends. Observational estimates indicate that the trend in the spatially averaged ?well observed? sea surface temperature (SST) due to the forced component has an approximately constant value of 0.1 K decade?1, while the IMP can contribute about ±0.08 K decade?1 for a 30-yr trend. The warming and cooling of the IMP matches that of the Atlantic multidecadal oscillation and is of sufficient amplitude to explain the acceleration in warming during 1977?2008 as compared to 1946?77, despite the forced component increasing at the same rate during these two periods. The amplitude and time scale of the IMP are such that its contribution to the trend dominates that of the forced component on time scales shorter than 16 yr, implying that the lack of warming trend during the past 10 yr is not statistically significant. Furthermore, since the IMP varies naturally on multidecadal time scales, it is potentially predictable on decadal time scales, providing a scientific rationale for decadal predictions. While the IMP can contribute significantly to trends for periods of 30 yr or shorter, it cannot account for the 0.8°C warming that has been observed in the twentieth-century spatially averaged SST.
UR – https://doi.org/10.1175/2010JCLI3659.1
ER –

NR – 142
TY – JOUR
T1 – Changes in Aridity in Response to Warming Hiatus
AU – Guan, Xiaodan
AU – Huang, Jianping
AU – Guo, Ruixia
PY – 2016
JF – Journal of Meteorological Research
VL – 31
SP – 117
EP – 125
DO – 10.1007/s13351-017-6038-1
AB – The global warming trend slowdown or warming hiatus began around the year 2000 and has persisted for nearly 15 years. Most studies have focused on the interpretation underlying this temperature change. In this study, changes in the global aridity index (AI) were analyzed using a newly developed dynamical adjustment method that can successfully identify and separate dynamically induced and radiatively-forced aridity changes in the raw data. The AI and Palmer Drought Severity Index (PDSI) appeared a wetting zone over the mid-to-high latitudes of the Northern Hemisphere in recent decades. The dynamical adjustment analysis suggests that this wetting zone occurred in response to the global warming hiatus. The dynamically-induced AI (DAI) played a major role in the AI changes during the hiatus period, and its relationships with the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO) also indicate that different phases of the NAO, PDO, and AMO contributed to different performance of the DAI over the Northern Hemisphere. Although the aridity wetting over the mid-to-high latitudes may relieve long-term drying in certain regions, the hiatus is temporary, and so is the relief. Accelerated global warming will return when the NAO, PDO, and AMO revert to their opposite phases in the future, and the wetting zone is likely to disappear.
ER –

NR – 143
TY – JOUR
AU – Tan, Ming
PY – 2016
TI – Circulation background of climate patterns in the past millennium: Uncertainty analysis and re-reconstruction of ENSO-like state
JO – Science China Earth Sciences
SP – 1225
EP – 1241
VL – 59
IS – 6
AB – The question of whether or not global warming has paused since more than ten years ago, namely “warming hiatus”, has attracted the attention of climate science community including the IPCC. Some authors have attributed the “warming hiatus” to the internal changes in the climate system, i.e., the recombination of ocean-atmosphere circulations. Therefore, it is necessary to propose higher requirements on reconstructing circulation background of climate change for the past millennium. However, the analyses of changes in atmospheric circulation over the last millennium as well as the conclusions of related regional climate patterns are so widely different and contradictory, bringing uncertainties to our understanding of regional even global climate change to a great extent. On the other hand, in the last 10 years the high-precision U/Th-dated stalagmite oxygen isotope ratio (d18O) sequences provided an accurate chronological frame for the paleoclimate study of the middle and late Pleistocene, in which all authors from China took the Chinese stalagmite d18O as the summer monsoon index without exception. However, this point of view misleads the climate scientists into thinking that the stalagmite d18O can be as the proxy of precipitation amount. Nevertheless, it is well known that all of these records have a lot in common in the low frequency trend. However, most sequences cannot be calibrated by instrumental precipitation records, and thus the uncertainty of the climate research framework of China and even of the world has increased. Therefore, it is imperative for climatology to clarify the origin of contradiction and to reduce the uncertainty as early as possible. On the basis of analyzing the significance of stalagmite d18O in the monsoon regions of China, the author tries to propose a new circulation proxy in this paper: integrating the Chinese stalagmite oxygen isotope sequence to reconstruct the tropical Pacific sea surface temperature gradient, i.e., the large-scale ENSO-like state over the past millennium. Furthermore, the author speculates that it was warm in the modern times and the Medieval Period, but the circulation recombination was different in both periods. And this inference could be supported by the longer record since Last Glacial Maximum. In other words, the attribution analysis of the identical low-frequency trends of Chinese stalagmite d18O on a large scale shows that the ENSO-like state controls the climate change in the monsoon regions of China at different time scales (from interannual to century or even longer time scales). Wherein the important connection of circulations is the western Pacific subtropical high (WPSH), that is to say, besides the interannual and decadal time scales, the WPSH would possess the circulation mode on longer timescales. For example, we may discuss the change of the WPSH in the whole Holocene epoch, i.e., the half precession period. These discussions could make sense to the study of not only the paleoclimate but also the modern climate.
UR – https://doi.org/10.1007/s11430-015-5256-6
DO – 10.1007/s11430-015-5256-6
ER –

NR – 144
TY – JOUR
AU – Cheng, Lijing
AU – Zheng, Fei
AU – Zhu, Jiang
T1 – Distinctive ocean interior changes during the recent warming slowdown
PY – 2015
AB – The earth system experiences continuous heat input, but a “climate hiatus” of upper ocean waters has been observed in this century. This leads to a question: where is the extra heat going? Using four in situ observation datasets, we explore the ocean subsurface temperature changes from 2004 to 2013. The observations all show that the ocean has continued to gain heat in this century, which is indicative of anthropogenic global warming. However, a distinctive pattern of change in the interior ocean is observed. The sea surface (1–100?m) temperature has decreased in this century, accompanied by warming in the 101–300?m layer. This pattern is due to the changes in the frequency of El Niño and La Niña events (ENSO characteristics), according to both observations and CMIP5 model simulations. In addition, we show for the first time that the ocean subsurface within 301–700?m experienced a net cooling, indicative of another instance of variability in the natural ocean. Furthermore, the ocean layer of 701–1500?m has experienced significant warming.
SP – 14346
VL – 5
DO – 10.1038/srep14346
UR – http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4585812/
JF – Scientific Reports
ER –

NR – 145
TY – JOUR
AU – Jochner, Susanne
AU – Menzel, Annette
TI – Does flower phenology mirror the slowdown of global warming?
JO – Ecology and Evolution
VL – 5
IS – 11
UR – http://dx.doi.org/10.1002/ece3.1503
DO – 10.1002/ece3.1503
SP – 2284
EP – 2295
PY – 2015
AB – Although recent global warming trends in air temperature are not as pronounced as those observed only one decade ago, global mean temperature is still at a very high level. Does plant phenology – which is believed to be a suitable indicator of climate change – respond in a similar way, that is, does it still mirror recent temperature variations? We explored in detail long-term flowering onset dates of snowdrop, cherry, and lime tree and relevant spring temperatures at three sites in Germany (1901–2012) using the Bayesian multiple change-point approach. We investigated whether mean spring temperature changes were amplified or slowed down in the past decade and how plant phenology responded to the most recent temperature changes. Incorporating records with different end points (i.e., 2002 and 2012), we compared differences in trends and inferred possible differences caused by extrapolating phenological and meteorological data. The new multiple-change point approach is characterized by an enhanced structure and greater flexibility compared to the one change point model. However, the highest model probabilities for phenological (meteorological) records were still obtained for the one change point (linear) model. Marked warming trends in the recent decade were only revealed for mean temperatures of March to May, here better described with one or two change point models. In the majority of cases analyzed, changes in temperatures were well mirrored by phenological changes. However, temperatures in March to May were linked to less strongly advancing onset dates for lime tree flowering during the period 1901-2012, pointing to the likely influence of photoperiodic constraints or unfulfilled chilling requirements. Due to the slowdown of temperature increase, analyses conducted on records ending in 2002 demonstrated distinct differences when compared with records ending in 2012. Extrapolation of trends could therefore (along with the choice of the statistical method) lead to distinctly different results and most recent data should be integrated in order not to over- or underestimate future phenological changes.
ER –

NR – 146
TY – JOUR
AU – Dieng, Habib B.
AU – Palanisamy, Hindumathi
AU – Cazenave, Anny
AU – Meyssignac, Benoit
AU – von Schuckmann, Karina
PY – 2015
TI – The Sea Level Budget Since 2003: Inference on the Deep Ocean Heat Content
JO – Surveys in Geophysics
SP – 209
EP – 229
VL – 36
IS – 2
AB – This study provides an overview of the various components of the global mean sea level evolution over two time spans: (1) 2005–2012 (corresponding to the full deployment of the Argo program) and (2) 2003–2012. Using a sea level budget approach, we compare altimetry-based global mean sea level, global ocean mass from GRACE space gravimetry and steric sea level from Argo and other in situ measurements. One goal of this study is to investigate whether it is possible to constrain the deep ocean contribution to the global mean sea level rise over the last decade. This question is particularly relevant, considering the current debate about the ‘hiatus,’ i.e., the observed recent pause of the global mean air and sea surface temperature evolution while the planet is still in thermal imbalance. We consider a total of 16 different data sets. Differences are noticed between data sets related to each variable (sea level, ocean mass and steric sea level), mostly due to data processing issues. Therefore, we perform the analysis using averages of the available data sets. For each period, we find that, when removing from the global mean sea level, the contributions of the global mean ocean mass and steric sea level (estimated for the 0–1,500 m ocean layer), there remains a residual signal displaying a positive slope of 0.3 ± 0.6 and 0.55 ± 0.6 mm/year over 2005–2012 and 2003–2012, respectively. Comparing with an ocean reanalysis and according to direct (but sparse) ocean temperature measurements below 1,500 m, it seems unlikely that the observed residual signal can be attributed to deep (below 1,500 m) ocean warming, in agreement with other recently published results. We estimate that it possibly reflects, at least partly, the signature of a missing upper ocean steric signal in regions uncovered by current observing systems. Our study also shows a steady warming increase since 2003 of the 700–1,500 m ocean layer (amounting ~0.2 mm/year in steric sea level equivalent), confirming previous findings, but seen in our study in each of the eight different steric data sets considered.
UR – https://doi.org/10.1007/s10712-015-9314-6
DO – 10.1007/s10712-015-9314-6
ER –

NR – 147
TY – JOUR
AU – Ying, Lingxiao
AU – Shen, Zehao
AU – Piao, Shilong
TI – The recent hiatus in global warming of the land surface: Scale-dependent breakpoint occurrences in space and time
JO – Geophysical Research Letters
VL – 42
IS – 15
UR – http://dx.doi.org/10.1002/2015GL064884
DO – 10.1002/2015GL064884
SP – 6471
EP – 6478
PY – 2015
AB – The spatial and temporal variability of the recent land warming hiatus have seldom been explored, despite their importance for understanding the mechanisms underlying the phenomenon. In this study, we applied piecewise linear regression to investigate the spatiotemporal patterns of the breakpoint time of warming over 40?years (1974–2013). Our results showed that at the global scale, mean annual temperature (MAT) over the land increased significantly until 2005 and that the warming trend then stalled. However, the breakpoint time of the warming varied greatly among different seasons and continents. We found no statistically significant breakpoint in MAT over the Northern Hemisphere, but MAT over the Southern Hemisphere showed a significant breakpoint (P? 0.5), with root mean squared error 1500m. The Hilbert spectrum from the OHC in the Labrador Sea interior reveals two important components at frequencies of 0.8-1.2cycleyr-1 (T=0.8–1.25 years) and 0.1-0.3cycleyr-1 (T=3.3–10 years), respectively, superimposed on the warming trends. The former corresponds to the dominant seasonal cycle due to surface heating, while the latter is concomitant with the timing of the reoccurrence of convective events. We also found that the cumulative North Atlantic Oscillation (NAO) index significantly correlates to the low-frequency OHC variations. Therefore, the interannual signals in the Labrador Sea at especially the intermediate layers are attributed to changes in the deep convective processes and the atmospheric conditions. By comparing with an extended OHC record (1945–2010), it was further shown that the warming trends obtained from the 10-year Argo record are part of multi-decadal variations that presumably reflect the Atlantic Multi-decadal Oscillation (AMO). In addition, the recent OHC changes in the Labrador Sea (i.e., increased heat in the deeper layers) may be related to the current global warming hiatus, suggesting the potential contributions from the Atlantic Meridional Overturning Circulation (AMOC) to the low-frequency OHC in the Labrador Sea.
ER –

NR – 148
TY – JOUR
AU – Regayre, L. A.
AU – Pringle, K. J.
AU – Booth, B. B. B.
AU – Lee, L. A.
AU – Mann, G. W.
AU – Browse, J.
AU – Woodhouse, M. T.
AU – Rap, A.
AU – Reddington, C. L.
AU – Carslaw, K. S.
TI – Uncertainty in the magnitude of aerosol-cloud radiative forcing over recent decades
JO – Geophysical Research Letters
VL – 41
IS – 24
UR – http://dx.doi.org/10.1002/2014GL062029
DO – 10.1002/2014GL062029
SP – 9040
EP – 9049
PY – 2014
AB – Aerosols and their effect on the radiative properties of clouds are one of the largest sources of uncertainty in calculations of the Earth’s energy budget. Here the sensitivity of aerosol-cloud albedo effect forcing to 31 aerosol parameters is quantified. Sensitivities are compared over three periods; 1850–2008, 1978–2008, and 1998–2008. Despite declining global anthropogenic SO2 emissions during 1978–2008, a cancelation of regional positive and negative forcings leads to a near-zero global mean cloud albedo effect forcing. In contrast to existing negative estimates, our results suggest that the aerosol-cloud albedo effect was likely positive (0.006 to 0.028Wm-2) in the recent decade, making it harder to explain the temperature hiatus as a forced response. Proportional contributions to forcing variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain forcing estimates, the processes that dominate uncertainty on the timescale of interest must be better understood.
ER –

NR – 149
TY – JOUR
AU – Sévellec, F.
AU – Sinha, B.
AU – Skliris, N.
TI – The rogue nature of hiatuses in a global warming climate
JO – Geophysical Research Letters
VL – 43
IS – 15
UR – http://dx.doi.org/10.1002/2016GL068950
DO – 10.1002/2016GL068950
SP – 8169
EP – 8177
PY – 2016
AB – The nature of rogue events is their unlikelihood and the recent unpredicted decade-long slowdown in surface warming, the so-called hiatus, may be such an event. However, given decadal variability in climate, global surface temperatures were never expected to increase monotonically with increasing radiative forcing. Here surface air temperature from 20 climate models is analyzed to estimate the historical and future likelihood of hiatuses and “surges” (faster than expected warming), showing that the global hiatus of the early 21st century was extremely unlikely. A novel analysis of future climate scenarios suggests that hiatuses will almost vanish and surges will strongly intensify by 2100 under a “business as usual” scenario. For “CO2 stabilisation” scenarios, hiatus, and surge characteristics revert to typical 1940s values. These results suggest to study the hiatus of the early 21st century and future reoccurrences as rogue events, at the limit of the variability of current climate modelling capability.
ER –

NR – 150
TY – JOUR
T1 – Variations of the Global Net Air–Sea Heat Flux during the “Hiatus” Period (2001–10)
AU – Liang, Xinfeng
AU – Yu, Lisan
PY – 2016
DO – 10.1175/JCLI-D-15-0626.1
JF – Journal of Climate
SP – 3647
EP – 3660
VL – 29
IS – 10
AB – An assessment is made of the mean and variability of the net air?sea heat flux, Qnet, from four products (ECCO, OAFlux?CERES, ERA-Interim, and NCEP1) over the global ice-free ocean from January 2001 to December 2010. For the 10-yr ?hiatus? period, all products agree on an overall net heat gain over the global ice-free ocean, but the magnitude varies from 1.7 to 9.5 W m?2. The differences among products are particularly large in the Southern Ocean, where they cannot even agree on whether the region gains or loses heat on the annual mean basis. Decadal trends of Qnet differ significantly between products. ECCO and OAFlux?CERES show almost no trend, whereas ERA-Interim suggests a downward trend and NCEP1 shows an upward trend. Therefore, numerical simulations utilizing different surface flux forcing products will likely produce diverged trends of the ocean heat content during this period. The downward trend in ERA-Interim started from 2006, driven by a peculiar pattern change in the tropical regions. ECCO, which used ERA-Interim as initial surface forcings and is constrained by ocean dynamics and ocean observations, corrected the pattern. Among the four products, ECCO and OAFlux?CERES show great similarities in the examined spatial and temporal patterns. Given that the two estimates were obtained using different approaches and based on largely independent observations, these similarities are encouraging and instructive. It is more likely that the global net air?sea heat flux does not change much during the so-called hiatus period.
UR – https://doi.org/10.1175/JCLI-D-15-0626.1
ER –

NR – 151
TY – JOUR
AU – Wang, You-Lin
AU – Wu, Chau-Ron
AU – Chao, Shenn-Yu
TI – Warming and weakening trends of the Kuroshio during 1993–2013
JO – Geophysical Research Letters
VL – 43
IS – 17
UR – http://dx.doi.org/10.1002/2016GL069432
DO – 10.1002/2016GL069432
SP – 9200
EP – 9207
PY – 2016
AB – Global warming seems leveling off somewhat during 1993–2013 despite increasing atmospheric greenhouse gases. What has happened to the Kuroshio Current system concurrently? Available independent data sets from 1993 to 2013 point to a single answer. Here we show a systemwide weakened Kuroshio during the period despite enhanced warming along its path. The Pacific warm pool upstream of the Kuroshio is still becoming warmer during the period. It injects more heat into the Current despite the weakened Kuroshio, which is associated with weakened westerlies and cyclonic trends of basin-scale wind stress curl. The weakened Kuroshio will modulate heat and mass exchanges between the tropics and extratropics, impacting the energy balance of climate system. It will also significantly influence mass, heat, salinity, and nutrient exchanges between the Pacific and adjacent marginal seas, which in turn impacts the regional weather, fisheries, and environments.
ER –

NR – 152
TY – JOUR
AU – Pretis, Felix
AU – Mann, Michael L.
AU – Kaufmann, Robert K.
PY – 2015
TI – Testing competing models of the temperature hiatus: assessing the effects of conditioning variables and temporal uncertainties through sample-wide break detection
JO – Climatic Change
SP – 705
EP – 718
VL – 131
IS – 4
AB – Explaining the recent slowdown in the rise of global mean surface temperature (the hiatus in warming) has become a major focus of climate research. Efforts to identify the causes of the hiatus that compare simulations from experiments run by climate models raise several statistical issues. Specifically, it is necessary to identify whether an experiment’s inability to simulate the hiatus is unique to this period or reflects a more systematic failure throughout the sample period. Furthermore, efforts to attribute the hiatus to a particular factor by including that mechanism in an experimental treatment must improve the model’s performance in a statistically significant manner at the time of the hiatus. Sample-wide assessments of simulation errors can provide an accurate assessment of whether or not the control experiment uniquely fails at the hiatus, and can identify its causes using experimental treatments. We use this approach to determine if the hiatus constitutes a unique failure in simulated climate models and to re- examine the conclusion that the hiatus is uniquely linked to episodes of La Niña-like cooling (Kosaka and Xie 2013). Using statistical techniques that do not define the hiatus a priori, we find no evidence that the slowdown in temperature increases are uniquely tied to episodes of La Niña-like cooling.
UR – https://doi.org/10.1007/s10584-015-1391-5
DO – 10.1007/s10584-015-1391-5
ER –

NR – 153
TY – JOUR
TI – Weakening of the Kuroshio Intrusion Into the South China Sea Under the Global Warming Hiatus
SP – 5064
EP – 5070
AU – C. R. Wu
AU – Y. L. Wang
AU – Y. F. Lin
AU – T. L. Chiang
AU – C. C. Wu
PY – 2016
DO – 10.1109/JSTARS.2016.2574941
JO – IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
IS – 11
VL – 9
AB – We analyze a 22-year (1993-2014) record of the Kuroshio intrusion (KI) index defined from maps of mean absolute dynamic topography west of Luzon Island in the Philippines to investigate the long-term trend of the KI into the South China Sea (SCS). The monotonically increasing trend of the KI index extracted by empirical mode decomposition implies a slight decreasing trend of the meridional pressure gradient across the Luzon Strait, suggesting a weakening of the KI into the SCS based on the geostrophy. This weakening is largely due to an intensification of the upstream Kuroshio east of Luzon, which is closely correlated with the latitude of the North Equatorial Current (NEC) bifurcation off the Philippines. We also find that the latitude of the NEC bifurcation has tended to migrate southward in recent years, coincident with the strengthening of the Kuroshio east of Luzon. The forcing of the trends of low-latitude circulation is attributable to changing surface wind fields in the tropical Pacific. The trade winds have intensified in response to the recent global warming hiatus, and an anomalous cyclonic wind field has appeared over the Philippine Sea. Both of these phenomena have contributed to the southward migration of the NEC bifurcation latitude in recent years. This has led to enhance the Kuroshio transport east of Luzon, and the Kuroshio has tended to bypass the Luzon Strait without significant westward encroachment.
ER –

NR – 154
TY – JOUR
AU – Vuille, Mathias
AU – Franquist, Eric
AU – Garreaud, René
AU – Lavado Casimiro, Waldo Sven
AU – Cáceres, Bolivar
TI – Impact of the global warming hiatus on Andean temperature
JO – Journal of Geophysical Research: Atmospheres
VL – 120
IS – 9
UR – http://dx.doi.org/10.1002/2015JD023126
DO – 10.1002/2015JD023126
SP – 3745
EP – 3757
PY – 2015
AB – The recent hiatus in global warming is likely to be reflected in Andean temperature, given its close dependence on tropical Pacific sea surface temperature (SST). While recent work in the subtropical Andes has indeed documented a cooling along coastal areas, trends in the tropical Andes show continued warming. Here we analyze spatiotemporal temperature variability along the western side of the Andes with a dense station network updated to 2010 and investigate its linkages to tropical Pacific modes of variability. Results indicate that the warming in tropical latitudes has come to a halt and that the subtropical regions continue to experience cooling. Trends, however, are highly dependent on elevation. While coastal regions experience cooling, higher elevations continue to warm. The coastal cooling is consistent with the observed Pacific Decadal Oscillation (PDO) fingerprint and can be accurately simulated using a simple PDO-analog model. Much of the PDO imprint is modulated and transmitted through adjustments in coastal SST off western South America. At inland and higher-elevation locations, however, temperature trends start to diverge from this PDO-analog model in the late 1980s and have by now emerged above the 1s model spread. Future warming at higher elevation is likely and will contribute to further vertical stratification of atmospheric temperature trends. In coastal locations, future warming or cooling will depend on the potential future intensification of the South Pacific anticyclone but also on continued temperature dependence on the state of the PDO.
ER –

NR – 155
TY – JOUR
AU – Gu, Guojun
AU – Adler, Robert F.
AU – Huffman, George J.
PY – 2016
TI – Long-term changes/trends in surface temperature and precipitation during the satellite era (1979–2012)
JO – Climate Dynamics
SP – 1091
EP – 1105
VL – 46
IS – 3
AB – During the post-1979 period in which the satellite-based precipitation measurements with global coverage are available, global mean surface temperature rapidly increased up to late 1990s, followed by a period of temperature hiatus after about 1998/1999. Comparing observed surface temperature trends against the simulated ones by the CMIP5 historical experiments especially in the zonal mean context suggests that although the anthropogenic greenhouse-gases (GHG) forcing has played a major role, in addition to the anthropogenic aerosols and various natural forcings, the effects from decadal-to-interdecadal-scale internal modes specifically the Pacific Decadal Oscillation (PDO) are also very strong. Evident temperature changes associated with the PDO’s phase shift are seen in the Pacific basin, with decadal-scale cooling in the tropical central-eastern Pacific and most of the east basin and concurrent warming in the subtropics of both hemispheres, even though the PDO’s net effect on global mean temperature is relatively weak. The Atlantic Multidecadal Oscillation (AMO) also changed its phase in the mid-1990s, and hence its possible impact is estimated and assessed as well. However, comparisons with CMIP5 simulations suggest that the AMO may have not contributed as significantly as the PDO in terms of the changes/trends in global surface temperature, even though the data analysis technique used here suggests otherwise. Long-term precipitation changes or trends during the post-1979 period are further shown to have been modulated by the two major factors: anthropogenic GHG and PDO, in addition to the relatively weak effects from aerosols and natural forcings. The spatial patterns of observed precipitation trends in the Pacific, including reductions in the tropical central-eastern Pacific and increases in the tropical western Pacific and along the South Pacific Convergence Zone, manifest the PDO’s contributions. Removing the PDO effect from the total precipitation trends makes the spatial structures of precipitation trends more similar to those simulated by CMIP5 historical full forcing experiments particularly in the context of zonal-mean results. This also confirms that in spite of the PDO effect specifically on regional scales, the anthropogenic GHG signals are still discernible in observed precipitation during the time period. Following the increase of GHG, precipitation tends to increase roughly along the climatological ITCZ and decrease south of the equator and in the subtropics of both hemispheres.
UR – https://doi.org/10.1007/s00382-015-2634-x
DO – 10.1007/s00382-015-2634-x
ER –

NR – 156
TY – JOUR
AU – Lee, Sang-Ki
AU – Park, Wonsun
AU – Baringer, Molly O.
AU – Gordon, Arnold L.
AU – Huber, Bruce
AU – Liu, Yanyun
TI – Pacific origin of the abrupt increase in Indian Ocean heat content during the warming hiatus
JA – Nature Geoscience
PY – 2015
VL – 8
SP – 445
UR – http://dx.doi.org/10.1038/ngeo2438
DO – 10.1038/ngeo2438
AB – Global mean surface warming has stalled since the end of the twentieth century1,2, but the net radiation imbalance at the top of the atmosphere continues to suggest an increasingly warming planet. This apparent contradiction has been reconciled by an anomalous heat flux into the ocean3,4,5,6,7,8, induced by a shift towards a La Niña-like state with cold sea surface temperatures in the eastern tropical Pacific over the past decade or so. A significant portion of the heat missing from the atmosphere is therefore expected to be stored in the Pacific Ocean. However, in situ hydrographic records indicate that Pacific Ocean heat content has been decreasing9. Here, we analyse observations along with simulations from a global ocean–sea ice model to track the pathway of heat. We find that the enhanced heat uptake by the Pacific Ocean has been compensated by an increased heat transport from the Pacific Ocean to the Indian Ocean, carried by the Indonesian throughflow. As a result, Indian Ocean heat content has increased abruptly, which accounts for more than 70% of the global ocean heat gain in the upper 700 m during the past decade. We conclude that the Indian Ocean has become increasingly important in modulating global climate variability.
ER –

NR – 157
TY – JOUR
AU – Roberts, C. D.
AU – Palmer, M. D.
AU – McNeall, D.
AU – Collins, M.
TI – Quantifying the likelihood of a continued hiatus in global warming
JF – Nature Climate Change
PY – 2015
VL – 5
SP – 337
UR – http://dx.doi.org/10.1038/nclimate2531
DO – 10.1038/nclimate2531
AB – Since the end of the twentieth century, global mean surface temperature has not risen as rapidly as predicted by global climate models1,2,3 (GCMs). This discrepancy has become known as the global warming ‘hiatus’ and a variety of mechanisms1,4,5,6,7,8,9,10,11,12,13,14,15,16,17 have been proposed to explain the observed slowdown in warming. Focusing on internally generated variability, we use pre-industrial control simulations from an observationally constrained ensemble of GCMs and a statistical approach to evaluate the expected frequency and characteristics of variability-driven hiatus periods and their likelihood of future continuation. Given an expected forced warming trend of ~0.2 K per decade, our constrained ensemble of GCMs implies that the probability of a variability-driven 10-year hiatus is ~10%, but less than 1% for a 20-year hiatus. Although the absolute probability of a 20-year hiatus is small, the probability that an existing 15-year hiatus will continue another five years is much higher (up to 25%). Therefore, given the recognized contribution of internal climate variability to the reduced rate of global warming during the past 15 years, we should not be surprised if the current hiatus continues until the end of the decade. Following the termination of a variability-driven hiatus, we also show that there is an increased likelihood of accelerated global warming associated with release of heat from the sub-surface ocean and a reversal of the phase of decadal variability in the Pacific Ocean.
ER –

NR – 158
TY – JOUR
AU – Notaro, Michael
AU – Yu, Yan
AU – Kalashnikova, Olga V.
TI – Regime shift in Arabian dust activity, triggered by persistent Fertile Crescent drought
JO – Journal of Geophysical Research: Atmospheres
VL – 120
IS – 19
UR – http://dx.doi.org/10.1002/2015JD023855
DO – 10.1002/2015JD023855
SP – 10,229
EP – 10,249
PY – 2015
AB – The Arabian Peninsula has experienced pronounced interannual to decadal variability in dust activity, including an abrupt regime shift around 2006 from an inactive dust period during 1998–2005 to an active period during 2007–2013. Corresponding in time to the onset of this regime shift, the climate state transitioned into a combined La Niña and negative phase of the Pacific Decadal Oscillation, which incited a hiatus in global warming in the 2000s. Superimposed upon a long-term regional drying trend, synergistic interactions between these teleconnection modes triggered the establishment of a devastating and prolonged drought, which engulfed the Fertile Crescent, namely, Iraq and Syria, and led to crop failure and civil unrest. Dried soils and diminished vegetation cover in the Fertile Crescent, as evident through remotely sensed enhanced vegetation indices, supported greater dust generation and transport to the Arabian Peninsula in 2007–2013, as identified both in increased dust days observed at weather stations and enhanced remotely sensed aerosol optical depth. According to backward trajectory analysis of dust days on the Arabian Peninsula, increased dust lifting and atmospheric dust concentration in the Fertile Crescent during this recent, prolonged drought episode supported a greater frequency of dust events across the peninsula with associated northerly trajectories and led to the dust regime shift. These findings are particularly concerning, considering projections of warming and drying for the eastern Mediterranean region and potential collapse of the Fertile Crescent during this century.
ER –

NR – 159
TY – JOUR
AU – Meehl, Gerald A.
AU – Teng, Haiyan
TI – Regional precipitation simulations for the mid-1970s shift and early-2000s hiatus
JO – Geophysical Research Letters
VL – 41
IS – 21
UR – http://dx.doi.org/10.1002/2014GL061778
DO – 10.1002/2014GL061778
SP – 7658
EP – 7665
PY – 2014
AB – It has been demonstrated that climate models initialized with observations produce better simulations of Pacific sea surface temperature (SST) patterns than uninitialized simulations for the two major climate regime changes of the last 40?years, the mid-1970s climate shift and early-2000s hiatus. A fundamental feature of these hindcasts is the simulation of the SST anomalies associated with the phase of the Interdecadal Pacific Oscillation (IPO). Since regional precipitation patterns over selected land areas in south Asia, Australia, and North America are known to be affected by SST patterns over the Pacific, it is shown that the initialized climate model simulations produce qualitatively better agreement with observations for regional precipitation anomalies in those regions compared to uninitialized climate models. Though the signals are small, the anomalies are consistent with our physical process-based understanding of precipitation responses over certain land areas during different IPO phases.
ER –

NR – 160
TY – JOUR
AU – Zhu, Yali
AU – Wang, Tao
AU – Wang, Huijun
PY – 2016
TI – Relative contribution of the anthropogenic forcing and natural variability to the interdecadal shift of climate during the late 1970s and 1990s
JO – Science Bulletin
SP – 416
EP – 424
VL – 61
IS – 5
AB – Global warming accelerated after the late 1970s and slowed down after the late 1990s, accompanying the significant interdecadal changes in the regional climate. We hypothesized that the interdecadal changes linearly consisted of two independent components, anthropogenic forcing and natural decadal variability, which can be represented simply by the radiative forcing effect of carbon dioxide (RF CO 2 ) (RFCO2) and the Pacific Decadal Oscillation (PDO), respectively. The combined effect of the RF CO 2 RFCO2 and PDO could explain the majority of the surface temperature changes during the late 1970s and 1990s, but the magnitudes of the relative contribution of the RF CO 2 RFCO2 and the PDO are inconsistent in different regions. For both the surface temperature and geopotential height, the RF CO 2 RFCO2 could induce significantly positive anomalies over almost the entire globe for these two shifts, exhibiting a larger magnitude in the mid–high latitudes and in the late 1990s shift. The PDO could induce opposite anomalies for the two interdecadal shifts due to its phase transitions (negative-positive–negative). Furthermore, for the shift in the late 1970s, both the RF CO 2 RFCO2 (53.7 %–66.7 %) and the PDO (33.3 %–46.3 %) were important in regulating the tropical geopotential height, whereas the RF CO 2 RFCO2 dominated the changes in the mid-latitudes. For the western Pacific subtropical high, the RF CO 2 RFCO2 (PDO) could explain 52.3 %–62.1 % (37.9 %–47.7 %) of the change. The negative effect of the PDO counteracted most of the RF CO 2 RFCO2 effects for the late 1990s shift.
UR – https://doi.org/10.1007/s11434-016-1012-3
DO – 10.1007/s11434-016-1012-3
ER –

NR – 161
TY – JOUR
AU – Song, Jinjie
AU – Wang, Yuan
AU – Tang, Jianping
TI – A Hiatus of the Greenhouse Effect
JF – Scientific Reports
PY – 2016
VL – 6
SP – 33315
UR – http://dx.doi.org/10.1038/srep33315
DO – 10.1038/srep33315
AB – The rate at which the global average surface temperature is increasing has slowed down since the end of the last century. This study investigates whether this warming hiatus results from a change in the well-known greenhouse effect. Using long-term, reliable, and consistent observational data from the Earth’s surface and the top of the atmosphere (TOA), two monthly gridded atmospheric and surface greenhouse effect parameters (Ga and Gs) are estimated to represent the radiative warming effects of the atmosphere and the surface in the infrared range from 1979 to 2014. The atmospheric and surface greenhouse effect over the tropical monsoon-prone regions is found to contribute substantially to the global total. Furthermore, the downward tendency of cloud activity leads to a greenhouse effect hiatus after the early 1990?s, prior to the warming pause. Additionally, this pause in the greenhouse effect is mostly caused by the high number of La Niña events between 1991 and 2014. A strong La Niña indicates suppressed convection in the tropical central Pacific that reduces atmospheric water vapor content and cloud volume. This significantly weakened regional greenhouse effect offsets the enhanced warming influence in other places and decelerates the rising global greenhouse effect. This work suggests that the greenhouse effect hiatus can be served as an additional factor to cause the recent global warming slowdown.
ER –

NR – 162
TY – JOUR
AU – Meehl, Gerald A.
AU – Arblaster, Julie M.
AU – Bitz, Cecilia M.
AU – Chung, Christine T. Y.
AU – Teng, Haiyan
TI – Antarctic sea-ice expansion between 2000 and 2014 driven by tropical Pacific decadal climate variability
JA – Nature Geoscience
PY – 2016
VL – 9
SP – 590
UR – http://dx.doi.org/10.1038/ngeo2751
DO – 10.1038/ngeo2751
AB – Antarctic sea-ice extent has been slowly increasing in the satellite record that began in 19791,2. Since the late 1990s, the increase has accelerated, but the average of all climate models shows a decline3. Meanwhile, the Interdecadal Pacific Oscillation, an internally generated mode of climate variability4, transitioned from positive to negative5, with an average cooling of tropical Pacific sea surface temperatures5, a slowdown of the global warming trend6,7,8 and a deepening of the Amundsen Sea Low near Antarctica1,9,10,11,12 that has contributed to regional circulation changes in the Ross Sea region and expansion of sea ice10. Here we show that the negative phase of the Interdecadal Pacific Oscillation in global coupled climate models is characterized by anomalies similar to the observed sea-level pressure and near-surface 850?hPa wind changes near Antarctica since 2000 that are conducive to expanding Antarctic sea-ice extent, particularly in the Ross Sea region in all seasons, involving a deepening of the Amundsen Sea Low. These atmospheric circulation changes are shown to be mainly driven by precipitation and convective heating anomalies related to the Interdecadal Pacific Oscillation in the equatorial eastern Pacific, with additional contributions from convective heating anomalies in the South Pacific convergence zone and tropical Atlantic regions.
ER –

NR – 163
TY – JOUR
T1 – Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures
JF – Science
SP – 988
LP – 991
DO – 10.1126/science.1257856
VL – 347
IS – 6225
AU – Steinman, Byron A.
AU – Mann, Michael E.
AU – Miller, Sonya K.
PY – 2015
UR – http://science.sciencemag.org/content/347/6225/988.abstract
AB – Which recent climate changes have been forced by greenhouse gas emissions, and which have been natural fluctuations of the climate system? Steinman et al. combined observational data and a large collection of climate models to assess the Northern Hemisphere climate over the past 150 years (see the Perspective by Booth). At various points in time, the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation have played particularly large roles in producing temperature trends. Their effects have combined to cause the apparent pause in warming at the beginning of the 21st century, known as the warming “hiatus.” This pause is projected to end in the near future as temperatures resume their upward climb.Science, this issue p. 988; see also p. 952 The recent slowdown in global warming has brought into question the reliability of climate model projections of future temperature change and has led to a vigorous debate over whether this slowdown is the result of naturally occurring, internal variability or forcing external to Earth’s climate system. To address these issues, we applied a semi-empirical approach that combines climate observations and model simulations to estimate Atlantic- and Pacific-based internal multidecadal variability (termed “AMO” and “PMO,” respectively). Using this method, the AMO and PMO are found to explain a large proportion of internal variability in Northern Hemisphere mean temperatures. Competition between a modest positive peak in the AMO and a substantially negative-trending PMO are seen to produce a slowdown or “false pause” in warming of the past decade.
ER –

NR – 164
TY – JOUR
AU – Visbeck, Martin
TI – Bumpy path to a warmer world
JA – Nature Geoscience
PY – 2014
VL – 7
SP – 160
UR – http://dx.doi.org/10.1038/ngeo2104
DO – 10.1038/ngeo2104
AB – Decadal climate variability has long received limited attention. With the slow-down in surface warming since the late 1990s, the decadal scale has rightly become a focus of attention: for assessing climate change and its impacts, it is of critical importance.
ER –

NR – 165
TY – JOUR
AU – Meehl, Gerald A.
AU – Hu, Aixue
AU – Santer, Benjamin D.
AU – Xie, Shang-Ping
TI – Contribution of the Interdecadal Pacific Oscillation to twentieth-century global surface temperature trends
JF – Nature Climate Change
PY – 2016
VL – 6
SP – 1005
UR – http://dx.doi.org/10.1038/nclimate3107
DO – 10.1038/nclimate3107
AB – Longer-term externally forced trends in global mean surface temperatures (GMSTs) are embedded in the background noise of internally generated multidecadal variability1. A key mode of internal variability is the Interdecadal Pacific Oscillation (IPO), which contributed to a reduced GMST trend during the early 2000s1,2,3. We use a novel, physical phenomenon-based approach to quantify the contribution from a source of internally generated multidecadal variability—the IPO—to multidecadal GMST trends. Here we show that the largest IPO contributions occurred in its positive phase during the rapid warming periods from 1910–1941 and 1971–1995, with the IPO contributing 71% and 75%, respectively, to the difference between the median values of the externally forced trends and observed trends. The IPO transition from positive to negative in the late-1990s contributed 27% of the discrepancy between model median estimates of the forced part of the GMST trend and the observed trend from 1995 to 2013, with additional contributions that are probably due to internal variability outside of the Pacific4 and an externally forced response from small volcanic eruptions5. Understanding and quantifying the contribution of a specific source of internally generated variability—the IPO—to GMST trends is necessary to improve decadal climate prediction skill.
ER –

NR – 166
TY – JOUR
AU – Balmaseda, Magdalena A.
AU – Trenberth, Kevin E.
AU – Källén, Erland
TI – Distinctive climate signals in reanalysis of global ocean heat content
JO – Geophysical Research Letters
VL – 40
IS – 9
UR – http://dx.doi.org/10.1002/grl.50382
DO – 10.1002/grl.50382
SP – 1754
EP – 1759
PY – 2013
AB – The elusive nature of the post-2004 upper ocean warming has exposed uncertainties in the ocean’s role in the Earth’s energy budget and transient climate sensitivity. Here we present the time evolution of the global ocean heat content for 1958 through 2009 from a new observation-based reanalysis of the ocean. Volcanic eruptions and El Niño events are identified as sharp cooling events punctuating a long-term ocean warming trend, while heating continues during the recent upper-ocean-warming hiatus, but the heat is absorbed in the deeper ocean. In the last decade, about 30% of the warming has occurred below 700 m, contributing significantly to an acceleration of the warming trend. The warming below 700 m remains even when the Argo observing system is withdrawn although the trends are reduced. Sensitivity experiments illustrate that surface wind variability is largely responsible for the changing ocean heat vertical distribution.
ER –

NR – 167
TY – JOUR
AU – Johansson, Daniel J. A.
AU – O’Neill, Brian C.
AU – Tebaldi, Claudia
AU – Häggström, Olle
TI – Equilibrium climate sensitivity in light of observations over the warming hiatus
JF – Nature Climate Change
PY – 2015
VL – 5
SP – 449
UR – http://dx.doi.org/10.1038/nclimate2573
DO – 10.1038/nclimate2573
AB – A key uncertainty in projecting future climate change is the magnitude of equilibrium climate sensitivity (ECS), that is, the eventual increase in global annual average surface temperature in response to a doubling of atmospheric CO2 concentration. The lower bound of the likely range for ECS given in the IPCC Fifth Assessment Report (AR5; refs 1, 2) was revised downwards to 1.5 °C, from 2 °C in its previous report3, mainly as an effect of considering observations over the warming hiatus—the period of slowdown of global average temperature increase since the early 2000s. Here we analyse how estimates of ECS change as observations accumulate over time and estimate the contribution of potential causes to the hiatus. We find that including observations over the hiatus reduces the most likely value for ECS from 2.8 °C to 2.5 °C, but that the lower bound of the 90% range remains stable around 2 °C. We also find that the hiatus is primarily attributable to El Niño/Southern Oscillation-related variability and reduced solar forcing.
ER –

NR – 168
TY – JOUR
A1 – Schleussner, C. F.
A1 – Runge, J.
A1 – Lehmann, J.
A1 – Levermann, A.
T1 – The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability
JA – Earth Syst. Dynam.
VL – 5
IS – 1
SP – 103
EP – 115
PY – 2014
UR – https://www.earth-syst-dynam.net/5/103/2014/
DO – 10.5194/esd-5-103-2014
AB – Earth’s climate exhibits internal modes of variability on various timescales. Here we investigate multi-decadal variability of the Atlantic meridional overturning circulation (AMOC), Northern Hemisphere sea-ice extent and global mean temperature (GMT) in an ensemble of CMIP5 models under control conditions. We report an inter-annual GMT variability of about ±0.1° C originating solely from natural variability in the model ensemble. By decomposing the GMT variance into contributions of the AMOC and Northern Hemisphere sea-ice extent using a graph-theoretical statistical approach, we find the AMOC to contribute 8% to GMT variability in the ensemble mean. Our results highlight the importance of AMOC sea-ice feedbacks that explain 5% of the GMT variance, while the contribution solely related to the AMOC is found to be about 3%. As a consequence of multi-decadal AMOC variability, we report substantial variations in North Atlantic deep-ocean heat content with trends of up to 0.7 × 1022 J decade-1 that are of the order of observed changes over the last decade and consistent with the reduced GMT warming trend over this period. Although these temperature anomalies are largely density-compensated by salinity changes, we find a robust negative correlation between the AMOC and North Atlantic deep-ocean density with density lagging the AMOC by 5 to 11 yr in most models. While this would in principle allow for a self-sustained oscillatory behavior of the coupled AMOC–deep- ocean system, our results are inconclusive about the role of this feedback in the model ensemble.
ER –

NR – 169
TY – JOUR
T1 – Extratropical Ocean Warming and Winter Arctic Sea Ice Cover since the 1990s
AU – Li, Fei
AU – Wang, Huijun
AU – Gao, Yongqi
PY – 2015
DO – 10.1175/JCLI-D-14-00629.1
JF – Journal of Climate
SP – 5510
EP – 5522
VL – 28
IS – 14
AB – Despite the fact that the Arctic Oscillation (AO) has reached a more neutral state and a global-warming hiatus has occurred in winter since the late 1990s, the Arctic sea ice cover (ASIC) still shows a pronounced decrease. This study reveals a close connection (R = 0.5) between the extratropical sea surface temperature (ET-SST) and ASIC in winter from 1994 to 2013. In response to one positive (negative) unit of deviation in the ET-SST pattern, the ASIC decreases (increases) in the Barents?Kara Seas and Hudson Bay (the Baffin Bay and Bering Sea) by 100?400 km2. This relationship might be maintained because of the impact of warming extratropical oceans on the polar vortex. Positive SST anomalies in the midlatitudes of the North Pacific and Atlantic (around 40°N) strengthen the equatorward planetary wave propagation, whereas negative SST anomalies in the high latitudes weaken the upward planetary wave propagation from the lower troposphere to the stratosphere. The former indicates a strengthening of the poleward meridional eddy momentum flux, and the latter implies a weakening of the poleward eddy heat flux, which favors an intensified upper-level polar night jet and a colder polar vortex, implying a stronger-than-normal polar vortex. Consequently, an anomalous cyclone emerges over the eastern Arctic, limiting or encouraging the ASIC by modulating the mean meridional heat flux. A possible reason for the long-term changes in the relationship between the ET-SST and ASIC is also discussed.
M3 – doi: 10.1175/JCLI-D-14-00629.1
UR – https://doi.org/10.1175/JCLI-D-14-00629.1
ER –

NR – 170
TY – JOUR
AU – Zhou, Yu
AU – Luo, Ming
AU – Leung, Yee
TI – On the detection of precipitation dependence on temperature
JO – Geophysical Research Letters
VL – 43
IS – 9
UR – http://dx.doi.org/10.1002/2016GL068811
DO – 10.1002/2016GL068811
SP – 4555
EP – 4565
PY – 2016
AB – Employing their newly proposed interannual difference method (IADM), Liu et al. (2009) and Shiu et al. (2012) reported a shocking increase of around 100% K-1 in heavy precipitation with warming global temperature in 1979–2007. Such increase is alarming and prompts us to probe into the IADM. In this study, both analytical derivations and numerical analyses demonstrate that IADM provides no additional information to that of the conventional linear regression, and also, it may give a false indication of dependence. For clarity and simplicity, we therefore recommend linear regression analysis over the IADM for the detection of dependence. We also find that heavy precipitation decreased during the global warming hiatus, and the precipitation dependence on temperature drops by almost 50% when the study period is extended to 1979–2014 and it may keep dropping in the near future. The risk of having heavy precipitation under warming global temperature may have been overestimated.
ER –

NR – 171
TY – JOUR
AU – Mann, Michael E.
AU – Steinman, Byron A.
AU – Miller, Sonya K.
AU – Frankcombe, Leela M.
AU – England, Matthew H.
AU – Cheung, Anson H.
TI – Predictability of the recent slowdown and subsequent recovery of large-scale surface warming using statistical methods
JO – Geophysical Research Letters
VL – 43
IS – 7
UR – http://dx.doi.org/10.1002/2016GL068159
DO – 10.1002/2016GL068159
SP – 3459
EP – 3467
PY – 2016
AB – The temporary slowdown in large-scale surface warming during the early 2000s has been attributed to both external and internal sources of climate variability. Using semiempirical estimates of the internal low-frequency variability component in Northern Hemisphere, Atlantic, and Pacific surface temperatures in concert with statistical hindcast experiments, we investigate whether the slowdown and its recent recovery were predictable. We conclude that the internal variability of the North Pacific, which played a critical role in the slowdown, does not appear to have been predictable using statistical forecast methods. An additional minor contribution from the North Atlantic, by contrast, appears to exhibit some predictability. While our analyses focus on combining semiempirical estimates of internal climatic variability with statistical hindcast experiments, possible implications for initialized model predictions are also discussed.
ER –

NR – 172
TY – JOUR
AU – You, Qinglong
AU – Min, Jinzhong
AU – Kang, Shichang
TI – Rapid warming in the Tibetan Plateau from observations and CMIP5 models in recent decades
JO – International Journal of Climatology
VL – 36
IS – 6
UR – http://dx.doi.org/10.1002/joc.4520
DO – 10.1002/joc.4520
SP – 2660
EP – 2670
PY – 2016
AB – On the basis of mean temperature, maximum temperature and minimum temperature from the updated China Homogenized Historical Temperature Data Sets, the recent warming in the Tibetan Plateau (TP) during 1961–2005 and global warming hiatus period are examined. During 1961–2005, the mean temperature, maximum temperature and minimum temperature in the whole TP show a statistically increasing trend especially after the 1980s, with the annual rates of 0.27, 0.19 and 0.36 °C decade-1, respectively. The performance of 26 general circulation models (GCMs) available in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) is evaluated in the TP by comparison with the observations during 1961–2005. Most CMIP5 GCMs can capture the decadal variations of the observed mean temperature, maximum temperature and minimum temperature, and have significant positive correlations with observations (R > 0.5), with root mean squared error 1500m. The Hilbert spectrum from the OHC in the Labrador Sea interior reveals two important components at frequencies of 0.8-1.2cycleyr-1 (T=0.8–1.25 years) and 0.1-0.3cycleyr-1 (T=3.3–10 years), respectively, superimposed on the warming trends. The former corresponds to the dominant seasonal cycle due to surface heating, while the latter is concomitant with the timing of the reoccurrence of convective events. We also found that the cumulative North Atlantic Oscillation (NAO) index significantly correlates to the low-frequency OHC variations. Therefore, the interannual signals in the Labrador Sea at especially the intermediate layers are attributed to changes in the deep convective processes and the atmospheric conditions. By comparing with an extended OHC record (1945–2010), it was further shown that the warming trends obtained from the 10-year Argo record are part of multi-decadal variations that presumably reflect the Atlantic Multi-decadal Oscillation (AMO). In addition, the recent OHC changes in the Labrador Sea (i.e., increased heat in the deeper layers) may be related to the current global warming hiatus, suggesting the potential contributions from the Atlantic Meridional Overturning Circulation (AMOC) to the low-frequency OHC in the Labrador Sea.
ER –

NR – 173
TY – JOUR
AU – Beniston, Martin
PY – 2015
TI – Ratios of record high to record low temperatures in Europe exhibit sharp increases since 2000 despite a slowdown in the rise of mean temperatures
JO – Climatic Change
SP – 225
EP – 237
VL – 129
IS – 1
AB – A study has been undertaken to analyze the behavior of record high and low values of temperature since the early 1950s for 30 locations spread across Europe. When establishing the ratios of the number of record Tmax to record Tmin values in each year, it is seen that there is a sharp increase in these ratios in the most recent decade. This seems to be an apparent paradox in view of the slow-down in atmospheric temperatures that has been observed since the early 2000s at both the hemispheric and European scales, but closer analysis suggests that the relationship between the record high:low ratios and mean annual temperatures is not linear but rather a square relationship. It is suggested that the record high to record low ratios in both the Mediterranean region and beyond 60° latitude north, observed in the most recent decade, may be related to an amplification of low-level atmospheric temperatures resulting from shorter snow seasons in the north and enhanced summer dryness in the south.
UR – https://doi.org/10.1007/s10584-015-1325-2
DO – 10.1007/s10584-015-1325-2
ER –

NR – 174
TY – JOUR
T1 – Decadal Climate Prediction: An Update from the Trenches
AU – Meehl, Gerald A.
AU – Goddard, Lisa
AU – Boer, George
AU – Burgman, Robert
AU – Branstator, Grant
AU – Cassou, Christophe
AU – Corti, Susanna
AU – Danabasoglu, Gokhan
AU – Doblas-Reyes, Francisco
AU – Hawkins, Ed
AU – Karspeck, Alicia
AU – Kimoto, Masahide
AU – Kumar, Arun
AU – Matei, Daniela
AU – Mignot, Juliette
AU – Msadek, Rym
AU – Navarra, Antonio
AU – Pohlmann, Holger
AU – Rienecker, Michele
AU – Rosati, Tony
AU – Schneider, Edwin
AU – Smith, Doug
AU – Sutton, Rowan
AU – Teng, Haiyan
AU – van Oldenborgh, Geert Jan
AU – Vecchi, Gabriel
AU – Yeager, Stephen
PY – 2013
DO – 10.1175/BAMS-D-12-00241.1
JF – Bulletin of the American Meteorological Society
SP – 243
EP – 267
VL – 95
IS – 2
AB – This paper provides an update on research in the relatively new and fast-moving field of decadal climate prediction, and addresses the use of decadal climate predictions not only for potential users of such information but also for improving our understanding of processes in the climate system. External forcing influences the predictions throughout, but their contributions to predictive skill become dominant after most of the improved skill from initialization with observations vanishes after about 6?9 years. Recent multimodel results suggest that there is relatively more decadal predictive skill in the North Atlantic, western Pacific, and Indian Oceans than in other regions of the world oceans. Aspects of decadal variability of SSTs, like the mid-1970s shift in the Pacific, the mid-1990s shift in the northern North Atlantic and western Pacific, and the early-2000s hiatus, are better represented in initialized hindcasts compared to uninitialized simulations. There is evidence of higher skill in initialized multimodel ensemble decadal hindcasts than in single model results, with multimodel initialized predictions for near-term climate showing somewhat less global warming than uninitialized simulations. Some decadal hindcasts have shown statistically reliable predictions of surface temperature over various land and ocean regions for lead times of up to 6?9 years, but this needs to be investigated in a wider set of models. As in the early days of El Niño?Southern Oscillation (ENSO) prediction, improvements to models will reduce the need for bias adjustment, and increase the reliability, and thus usefulness, of decadal climate predictions in the future.
M3 – doi: 10.1175/BAMS-D-12-00241.1
UR – https://doi.org/10.1175/BAMS-D-12-00241.1
ER –

NR – 175
TY – JOUR
AU – Thoma, Malte
AU – Greatbatch, Richard J.
AU – Kadow, Christopher
AU – Gerdes, Ruediger
TI – Decadal hindcasts initialized using observed surface wind stress: Evaluation and prediction out to 2024
JO – Geophysical Research Letters
VL – 42
IS – 15
UR – http://dx.doi.org/10.1002/2015GL064833
DO – 10.1002/2015GL064833
SP – 6454
EP – 6461
PY – 2015
AB – We use surface air temperature to evaluate the decadal forecast skill of the fully coupled Max Planck Institut Earth System Model (MPI-ESM) initialized using only surface wind stress applied to the ocean component of the model (Modini: Model initialization by partially coupled spin-up). Our analysis shows that the greenhouse gas forcing alone results in a significant forecast skill on the 2–5 and 6–9 year range even for uninitialized hindcasts. For the first forecast year, the forecast skill of Modini is generally comparable with previous initialization procedures applied to MPI-ESM. But only Modini is able to generate a significant skill (correlation) in the tropical Pacific for a 2–5 year (and to a lesser extent for a 6–9 year) hindcast. Modini is also better able to capture the observed hiatus in global warming in hindcast mode than the other methods. Finally, we present forecasts for 2015 and the average of years 2016–2019 and 2020–2024, predicting an end to the hiatus.
ER –

NR – 176
TY – JOUR
A1 – Boer, G. J.
A1 – Smith, D. M.
A1 – Cassou, C.
A1 – Doblas-Reyes, F.
A1 – Danabasoglu, G.
A1 – Kirtman, B.
A1 – Kushnir, Y.
A1 – Kimoto, M.
A1 – Meehl, G. A.
A1 – Msadek, R.
A1 – Mueller, W. A.
A1 – Taylor, K. E.
A1 – Zwiers, F.
A1 – Rixen, M.
A1 – Ruprich-Robert, Y.
A1 – Eade, R.
T1 – The Decadal Climate Prediction Project (DCPP) contribution to CMIP6
JA – Geosci. Model Dev.
VL – 9
IS – 10
SP – 3751
EP – 3777
PY – 2016
UR – https://www.geosci-model-dev.net/9/3751/2016/
DO – 10.5194/gmd-9-3751-2016
AB – The Decadal Climate Prediction Project (DCPP) is a coordinated multi-model investigation into decadal climate prediction, predictability, and variability. The DCPP makes use of past experience in simulating and predicting decadal variability and forced climate change gained from the fifth Coupled Model Intercomparison Project (CMIP5) and elsewhere. It builds on recent improvements in models, in the reanalysis of climate data, in methods of initialization and ensemble generation, and in data treatment and analysis to propose an extended comprehensive decadal prediction investigation as a contribution to CMIP6 (Eyring et al., 2016) and to the WCRP Grand Challenge on Near Term Climate Prediction (Kushnir et al., 2016). The DCPP consists of three components. Component A comprises the production and analysis of an extensive archive of retrospective forecasts to be used to assess and understand historical decadal prediction skill, as a basis for improvements in all aspects of end-to-end decadal prediction, and as a basis for forecasting on annual to decadal timescales. Component B undertakes ongoing production, analysis and dissemination of experimental quasi-real-time multi-model forecasts as a basis for potential operational forecast production. Component C involves the organization and coordination of case studies of particular climate shifts and variations, both natural and naturally forced (e.g. the “hiatus”, volcanoes), including the study of the mechanisms that determine these behaviours. Groups are invited to participate in as many or as few of the components of the DCPP, each of which are separately prioritized, as are of interest to them. The Decadal Climate Prediction Project addresses a range of scientific issues involving the ability of the climate system to be predicted on annual to decadal timescales, the skill that is currently and potentially available, the mechanisms involved in long timescale variability, and the production of forecasts of benefit to both science and society.
ER –

NR – 177
TY – JOUR
AU – Smith, Doug M.
AU – Allan, Richard P.
AU – Coward, Andrew C.
AU – Eade, Rosie
AU – Hyder, Patrick
AU – Liu, Chunlei
AU – Loeb, Norman G.
AU – Palmer, Matthew D.
AU – Roberts, Chris D.
AU – Scaife, Adam A.
TI – Earth’s energy imbalance since 1960 in observations and CMIP5 models
JO – Geophysical Research Letters
VL – 42
IS – 4
UR – http://dx.doi.org/10.1002/2014GL062669
DO – 10.1002/2014GL062669
SP – 1205
EP – 1213
PY – 2015
AB – Observational analyses of running 5 year ocean heat content trends (Ht) and net downward top of atmosphere radiation (N) are significantly correlated (r?~?0.6) from 1960 to 1999, but a spike in Ht in the early 2000s is likely spurious since it is inconsistent with estimates of N from both satellite observations and climate model simulations. Variations in N between 1960 and 2000 were dominated by volcanic eruptions and are well simulated by the ensemble mean of coupled models from the Fifth Coupled Model Intercomparison Project (CMIP5). We find an observation-based reduction in N of -? 0.31?±?0.21?W?m-2 between 1999 and 2005 that potentially contributed to the recent warming slowdown, but the relative roles of external forcing and internal variability remain unclear. While present-day anomalies of N in the CMIP5 ensemble mean and observations agree, this may be due to a cancelation of errors in outgoing longwave and absorbed solar radiation.
ER –

NR – 178
TY – JOUR
A1 – Piecuch, C. G.
A1 – Quinn, K. J.
T1 – El Niño, La Niña, and the global sea level budget
JA – Ocean Sci.
VL – 12
IS – 6
SP – 1165
EP – 1177
PY – 2016
UR – https://www.ocean-sci.net/12/1165/2016/
DO – 10.5194/os-12-1165-2016
AB – Previous studies show that nonseasonal variations in global-mean sea level (GMSL) are significantly correlated with El Niño–Southern Oscillation (ENSO). However, it has remained unclear to what extent these ENSO-related GMSL fluctuations correspond to steric (i.e., density) or barystatic (mass) effects. Here we diagnose the GMSL budget for ENSO events observationally using data from profiling floats, satellite gravimetry, and radar altimetry during 2005–2015. Steric and barystatic effects make comparable contributions to the GMSL budget during ENSO, in contrast to previous interpretations based largely on hydrological models, which emphasize the barystatic component. The steric contributions reflect changes in global ocean heat content, centered on the Pacific. Distributions of ocean heat storage in the Pacific arise from a mix of diabatic and adiabatic effects. Results have implications for understanding the surface warming slowdown and demonstrate the usefulness of the Global Ocean Observing System for constraining Earth’s hydrological cycle and radiation imbalance.
ER –

NR – 179
TY – JOUR
T1 – Varying temperature and heat content signatures in the central Labrador Sea at different layers and timescales
AU – Li, Feili
AU – Jo, Young-Heon
AU – Yan, Xiao-Hai
AU – Timothy Liu, W.
JO – Deep Sea Research Part I: Oceanographic Research Papers
VL – 103
SP – 114
EP – 124
PY – 2015
DO – https://doi.org/10.1016/j.dsr.2015.04.012
UR – http://www.sciencedirect.com/science/article/pii/S0967063715000862
AB – The dominant modes of variability in the temperature and ocean heat content (OHC; 0–1000m) of the central Labrador Sea were investigated using the Hilbert–Huang Transform (HHT) based on Argo profiles collected during 2003–2012. Warming trends of approximately 0.03°Cyr-1 were observed in the upper 2000m of the water column. A strong annual temperature cycle exists and dominates at the 500m depth, while signals at the interannual timescales can explain most of the temperature variability at the 1000m and 1500m depths. These interannual signals are closely correlated to the variability of deep convection in the Labrador Sea, which has intermittent enhancement of mixed layer depth (MLD)>1500m. The Hilbert spectrum from the OHC in the Labrador Sea interior reveals two important components at frequencies of 0.8-1.2cycleyr-1 (T=0.8–1.25 years) and 0.1-0.3cycleyr-1 (T=3.3–10 years), respectively, superimposed on the warming trends. The former corresponds to the dominant seasonal cycle due to surface heating, while the latter is concomitant with the timing of the reoccurrence of convective events. We also found that the cumulative North Atlantic Oscillation (NAO) index significantly correlates to the low-frequency OHC variations. Therefore, the interannual signals in the Labrador Sea at especially the intermediate layers are attributed to changes in the deep convective processes and the atmospheric conditions. By comparing with an extended OHC record (1945–2010), it was further shown that the warming trends obtained from the 10-year Argo record are part of multi-decadal variations that presumably reflect the Atlantic Multi-decadal Oscillation (AMO). In addition, the recent OHC changes in the Labrador Sea (i.e., increased heat in the deeper layers) may be related to the current global warming hiatus, suggesting the potential contributions from the Atlantic Meridional Overturning Circulation (AMOC) to the low-frequency OHC in the Labrador Sea.
ER –

NR – 180
TY – JOUR
T1 – Very early warning of next El Niño
JF – Proceedings of the National Academy of Sciences
SP – 2064
LP – 2066
DO – 10.1073/pnas.1323058111
VL – 111
IS – 6
AU – Ludescher, Josef
AU – Gozolchiani, Avi
AU – Bogachev, Mikhail I.
AU – Bunde, Armin
AU – Havlin, Shlomo
AU – Schellnhuber, Hans Joachim
PY – 2014
UR – http://www.pnas.org/content/111/6/2064.abstract
AB – The most important driver of climate variability is the El Niño Southern Oscillation, which can trigger disasters in various parts of the globe. Despite its importance, conventional forecasting is still limited to 6 mo ahead. Recently, we developed an approach based on network analysis, which allows projection of an El Niño event about 1 y ahead. Here we show that our method correctly predicted the absence of El Niño events in 2012 and 2013 and now announce that our approach indicated (in September 2013 already) the return of El Niño in late 2014 with a 3-in-4 likelihood. We also discuss the relevance of the next El Niño to the question of global warming and the present hiatus in the global mean surface temperature.
ER –

NR – 181
TY – JOUR
AU – Laepple, T.
AU – Huybers, P.
TI – Global and regional variability in marine surface temperatures
JO – Geophysical Research Letters
VL – 41
IS – 7
UR – http://dx.doi.org/10.1002/2014GL059345
DO – 10.1002/2014GL059345
SP – 2528
EP – 2534
PY – 2014
AB – The temperature variability simulated by climate models is generally consistent with that observed in instrumental records at the scale of global averages, but further insight can also be obtained from regional analysis of the marine temperature record. A protocol is developed for comparing model simulations to observations that account for observational noise and missing data. General consistency between Coupled Model Intercomparison Project Phase 5 model simulations and regional sea surface temperature variability is demonstrated at interannual timescales. At interdecadal timescales, however, the variability diagnosed from observations is significantly greater. Discrepancies are greatest at low latitudes, with none of the 41 models showing equal or greater interdecadal variability. The pattern of suppressed variability at longer timescales and smaller spatial scales appears consistent with models generally being too diffusive. Suppressed variability of low-latitude marine temperatures points to underestimation of intrinsic variability and may help explain why few models reproduce the observed temperature trends during the last 15?years.
ER –

NR – 182
TY – JOUR
AU – de Boisséson, E.
AU – Balmaseda, M. A.
AU – Abdalla, S.
AU – Källén, E.
AU – Janssen, P. A. E. M.
TI – How robust is the recent strengthening of the Tropical Pacific trade winds?
JO – Geophysical Research Letters
VL – 41
IS – 12
UR – http://dx.doi.org/10.1002/2014GL060257
DO – 10.1002/2014GL060257
SP – 4398
EP – 4405
PY – 2014
AB – The persistent strengthening of the trade winds over the Pacific Ocean over the past 20 years has recently been proposed as a driver for the increase of ocean heat uptake linked to the hiatus in surface global warming. Crucial aspects in this argument are the reliability of the wind signal, usually derived from atmospheric reanalyses, and the ability of models to represent it. This study addresses these two aspects by comparing various observations with reanalyses and model integrations from the European Centre for Medium-Range Weather Forecasts system. We show that the strengthening of trades over the Pacific is a robust feature in several observational data sets as well as in the reanalyses based on full and limited sets of observations. The wind trend is also reproduced in an atmospheric model integration forced by sea surface temperature analysis, a result that opens the doors to further investigation on the nature of the changes.
ER –

NR – 183
TY – JOUR
AU – Gleckler, Peter J.
AU – Durack, Paul J.
AU – Stouffer, Ronald J.
AU – Johnson, Gregory C.
AU – Forest, Chris E.
TI – Industrial-era global ocean heat uptake doubles in recent decades
JF – Nature Climate Change
PY – 2016
VL – 6
SP – 394
UR – http://dx.doi.org/10.1038/nclimate2915
DO – 10.1038/nclimate2915
AB – Formal detection and attribution studies have used observations and climate models to identify an anthropogenic warming signature in the upper (0–700?m) ocean1,2,3,4. Recently, as a result of the so-called surface warming hiatus, there has been considerable interest in global ocean heat content (OHC) changes in the deeper ocean, including natural and anthropogenically forced changes identified in observational5,6,7, modelling8,9 and data re- analysis10,11 studies. Here, we examine OHC changes in the context of the Earth’s global energy budget since early in the industrial era (circa 1865– 2015) for a range of depths. We rely on OHC change estimates from a diverse collection of measurement systems including data from the nineteenth-century Challenger expedition12, a multi-decadal record of ship-based in situ mostly upper-ocean measurements, the more recent near-global Argo floats profiling to intermediate (2,000?m) depths13, and full-depth repeated transoceanic sections5. We show that the multi-model mean constructed from the current generation of historically forced climate models is consistent with the OHC changes from this diverse collection of observational systems. Our model- based analysis suggests that nearly half of the industrial-era increases in global OHC have occurred in recent decades, with over a third of the accumulated heat occurring below 700?m and steadily rising.
ER –

NR – 184
TY – JOUR
AU – Liu, Qin-Yan
AU – Feng, Ming
AU – Wang, Dongxiao
AU – Wijffels, Susan
TI – Interannual variability of the Indonesian Throughflow transport: A revisit based on 30 year expendable bathythermograph data
JO – Journal of Geophysical Research: Oceans
VL – 120
IS – 12
UR – http://dx.doi.org/10.1002/2015JC011351
DO – 10.1002/2015JC011351
SP – 8270
EP – 8282
PY – 2015
AB – Based on 30 year repeated expendable bathythermograph (XBT) deployments between Fremantle, Western Australia, and the Sunda Strait, Indonesia, from 1984 to 2013, interannual variability of geostrophic transport of the Indonesian Throughflow (ITF) and its relationships with El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are investigated. The IOD induced coastal Kelvin waves propagate along the Sumatra-Java coast of Indonesia, and ENSO induced coastal Kelvin waves propagate along the northwest coast of Australia, both influencing interannual variations of the ITF transport. The ITF geostrophic transport is stronger during La Niña phase and weaker during El Niño phase, with the Niño3.4 index leading the ITF variability by 7 months. The Indian Ocean wind variability associated with the IOD to a certain extent offset the Pacific ENSO influences on the ITF geostrophic transport during the developing and mature phases of El Niño and La Niña, due to the covarying IOD variability with ENSO. The ITF geostrophic transport experiences a strengthening trend of about 1 Sv every 10 years over the study period, which is mostly due to a response to the strengthening of the trade winds in the Pacific during the climate change hiatus period. Decadal variations of the temperature-salinity relationships need to be considered when estimating the geostrophic transport of the ITF using XBT data.
ER –

NR – 185
TY – JOUR
AU – Li, Jianping
AU – Sun, Cheng
AU – Jin, Fei-Fei
TI – NAO implicated as a predictor of Northern Hemisphere mean temperature multidecadal variability
JO – Geophysical Research Letters
VL – 40
IS – 20
UR – http://dx.doi.org/10.1002/2013GL057877
DO – 10.1002/2013GL057877
SP – 5497
EP – 5502
PY – 2013
AB – The twentieth century Northern Hemisphere mean surface temperature (NHT) is characterized by a multidecadal warming-cooling-warming pattern followed by a flat trend since about 2000 (recent warming hiatus). Here we demonstrate that the North Atlantic Oscillation (NAO) is implicated as a useful predictor of NHT multidecadal variability. Observational analysis shows that the NAO leads both the detrended NHT and oceanic Atlantic Multidecadal Oscillation (AMO) by 15–20?years. Theoretical analysis illuminates that the NAO precedes NHT multidecadal variability through its delayed effect on the AMO due to the large thermal inertia associated with slow oceanic processes. An NAO-based linear model is therefore established to predict the NHT, which gives an excellent hindcast for NHT in 1971–2011 with the recent flat trend well predicted. NHT in 2012–2027 is predicted to fall slightly over the next decades, due to the recent NAO decadal weakening that temporarily offsets the anthropogenically induced warming.
ER –

NR – 186
TY – JOUR
T1 – Northwestern Pacific typhoon intensity controlled by changes in ocean temperatures
JF – Science Advances
DO – 10.1126/sciadv.1500014
VL – 1
IS – 4
AU – Mei, Wei
AU – Xie, Shang-Ping
AU – Primeau, François
AU – McWilliams, James C.
AU – Pasquero, Claudia
PY – 2015
UR – http://advances.sciencemag.org/content/1/4/e1500014.abstract
AB – Dominant climatic factors controlling the lifetime peak intensity of typhoons are determined from six decades of Pacific typhoon data. We find that upper ocean temperatures in the low-latitude northwestern Pacific (LLNWP) and sea surface temperatures in the central equatorial Pacific control the seasonal average lifetime peak intensity by setting the rate and duration of typhoon intensification, respectively. An anomalously strong LLNWP upper ocean warming has favored increased intensification rates and led to unprecedentedly high average typhoon intensity during the recent global warming hiatus period, despite a reduction in intensification duration tied to the central equatorial Pacific surface cooling. Continued LLNWP upper ocean warming as predicted under a moderate [that is, Representative Concentration Pathway (RCP) 4.5] climate change scenario is expected to further increase the average typhoon intensity by an additional 14% by 2100.
ER –

NR – 187
TY – JOUR
AU – Takahashi, Chiharu
AU – Watanabe, Masahiro
TI – Pacific trade winds accelerated by aerosol forcing over the past two decades
JF – Nature Climate Change
PY – 2016
VL – 6
SP – 768
UR – http://dx.doi.org/10.1038/nclimate2996
DO – 10.1038/nclimate2996
AB – The Pacific trade winds, coupled with the zonal sea surface temperature gradient in the equatorial Pacific Ocean, control regional sea levels1, and therefore their trend is a great concern in the Pacific Rim. Over the past two decades, easterly winds have been accelerated in association with eastern tropical Pacific cooling2. They may represent natural interdecadal variability in the Pacific3 and possibly explain the recent global warming hiatus4,5,6,7. However, the intensification of the winds has been the strongest ever observed in the past century2,5,8, the reason for which is still unclear. Here we show, using multiple climate simulations for 1921–2014 by a global climate model, that approximately one-third of the trade-wind intensification for 1991–2010 can be attributed to changes in sulfate aerosols. The multidecadal sea surface temperature anomaly induced mostly by volcanic aerosols dominates in the western North Pacific, and its sign changed rapidly from negative to positive in the 1990s, coherently with Atlantic multidecadal variability9,10,11. The western North Pacific warming resulted in intensification of trade winds to the west of the dateline. These trends have not contributed much to the global warming hiatus, but have greatly impacted rainfall over the western Pacific islands.
ER –

NR – 188
TY – JOUR
AU – Li, Xichen
AU – Xie, Shang-Ping
AU – Gille, Sarah T.
AU – Yoo, Changhyun
TI – Atlantic-induced pan-tropical climate change over the past three decades
JF – Nature Climate Change
PY – 2015
VL – 6
SP – 275
UR – http://dx.doi.org/10.1038/nclimate2840
DO – 10.1038/nclimate2840
AB – During the past three decades, tropical sea surface temperature (SST) has shown dipole-like trends, with warming over the tropical Atlantic and Indo-western Pacific but cooling over the eastern Pacific. Competing hypotheses relate this cooling, identified as a driver of the global warming hiatus1,2, to the warming trends in either the Atlantic3,4 or Indian Ocean5. However, the mechanisms, the relative importance and the interactions between these teleconnections remain unclear. Using a state-of-the-art climate model, we show that the Atlantic plays a key role in initiating the tropical-wide teleconnection, and the Atlantic-induced anomalies contribute ~55–75% of the tropical SST and circulation changes during the satellite era. The Atlantic warming drives easterly wind anomalies over the Indo-western Pacific as Kelvin waves and westerly anomalies over the eastern Pacific as Rossby waves. The wind changes induce an Indo-western Pacific warming through the wind–evaporation–SST effect6,7, and this warming intensifies the La Niña-type response in the tropical Pacific by enhancing the easterly trade winds and through the Bjerknes ocean dynamical processes8. The teleconnection develops into a tropical-wide SST dipole pattern. This mechanism, supported by observations and a hierarchy of climate models, reveals that the tropical ocean basins are more tightly connected than previously thought.
ER –

NR – 189
TY – JOUR
T1 – Climate Signals in the Mid- to High-Latitude North Atlantic from Altimeter Observations
AU – Li, Feili
AU – Jo, Young-Heon
AU – Yan, Xiao-Hai
AU – Liu, W. Timothy
PY – 2015
DO – 10.1175/JCLI-D-12-00670.1
JF – Journal of Climate
SP – 4905
EP – 4925
VL – 29
IS – 13
AB – The variability of the sea surface height anomaly (SSHA) in the mid- to high-latitude North Atlantic for the period of 1993?2010 was investigated using the ensemble empirical mode decomposition to identify the dominant time scales. Sea level variations in the North Atlantic subpolar gyre (SPG) are dominated by the annual cycle and the long-term increasing trend. In comparison, the SSHA along the Gulf Stream (GS) is dominated by variability at intraseasonal and annual time scales. Moreover, the sea level rise in the SPG developed at a reduced rate in the 2000s compared to rates in the 1990s, which was accompanied by a rebound in SSHA variability following a period of lower variability in the system. These changes in both apparent trend and low-frequency SSHA oscillations reveal the importance of low-frequency variability in the SPG. To identify the possible contributing factors for these changes, the heat content balance (equivalent variations in the sea level) in the subpolar region was examined. The results indicate that horizontal circulations may primarily contribute to the interannual to decadal variations, while the air?sea heat flux is not negligible at annual time scale. Furthermore, the low-frequency variability in the SPG relates to the propagation of Atlantic meridional overturning circulation (AMOC) variations from the deep-water formation region to midlatitudes in the North Atlantic, which might have the implications for recent global surface warming hiatus.
UR – https://doi.org/10.1175/JCLI-D-12-00670.1
ER –

NR – 190
TY – JOUR
TI – How Long will the Pause of Global Warming Stay Again?
AU – Bin, Huang Jian
AU – Yong, Luo
AU – Wu, Wang Shao
AU – Yu, Wen Xin
AU – Ci, Zhao Zong
PY – 2014
JO – Progressus Inquisitiones De Mutatione Climatis
VL – 10
IS – 6
SP – 465
EP – 468
DO – 10.3969/j.issn.1673-1719.2014.06.011
ER –

NR – 191
TY – JOUR
AU – Veettil, Bijeesh Kozhikkodan
AU – Pereira, Sebastián Felipe Ruiz
AU – Wang, Shanshan
AU – Valente, Pedro Teixeira
AU – Grondona, Atilio Efrain Bica
AU – Rondón, Adriana Coromoto Becerra Rondón
AU – Rekowsky, Isabel Cristiane
AU – de Souza, Sergio Florêncio
AU – Bianchini, Nilceia
AU – Bremer, Ulisses Franz
AU – Simões, Jefferson Cardia
TI – Un análisis comparativo del comportamiento diferencial de los glaciares en los Andes Tropicales usando teledetección
T2 – A comparative analysis of glacier retreat in the Tropical Andes using remote sensing
PY – 2016
JO – Investigaciones Geográficas
VL – 51
SP – 3
EP – 36
DO – 10.5354/0719-5370.2016.41215
UR – https://investigacionesgeograficas.uchile.cl/index.php/IG/article/view/41215
AB – In this research paper, we analysed the behaviour of Tropical Andean glaciers in a changing climate. We used multi-source satellite images as well as meteorological datasets to achieve this objective. Representative glaciers in four different climatic zones, namely the inner tropics, northern wet outer tropics, southern wet outer tropics and dry outer tropics, were considered in this study. Changes in annual maximum snowline during 1985 – 2015 and also the decadal changes in the area between 1975 and 2015 of these glaciers were calculated. Furthermore, we analysed the rate of glacier retreat during the occurrence of El Niño–Southern Oscillation and Pacific Decadal Oscillation. It is observed that the glaciers in both the inner and outer tropics underwent retreat during the study period and most of this retreat occurred during 1975 – 1997 which is parallel with the so-called Pacific shift. Exceptional variations in snowline altitude were observed when an El Niño event occurs during the warm phase of the Pacific Decadal Oscillation. No significant signals of the recent hiatus in global warming were observed, except in the dry outer tropics which are situated near the subtropical region.
ER –

NR – 192
TY – JOUR
TI – The Global Warming Hiatus Simulated in HadGEM2-AO Based on RCP8.5
AU – Wie, Jieun
AU – Moon, Byung-Kwon
AU – Kim, Ki-Young
AU – Lee, Johan
PY – 2014
JO – Journal of the Korean earth science society
VL – 35
IS – 4
SP – 249
EP – 258
DO – 10.5467/JKESS.2014.35.4.249
UR – http://www.koreascience.or.kr/article/ArticleFullRecord.jsp?cn=JGGHBA_2014_v35n4_249
AB – Despite the greenhouse gases like carbon dioxide have steadily increased in atmosphere, the overall trend of the global average surface air temperature has stalled during the last decade (2002-present). This phenomenon is often called hiatus or warming pause, which is challenging the prevailing view that anthropogenic forcing causes warming environment. Our study characterized the hiatus by analyzing the HadGEM2-AO (95 yrs) simulation data based on RCP8.5 scenario. The PC2 time series from the EOF of the zonal mean vertical ocean temperature has been defined as the index that represents the warming pause. The relationship between the hiatus, ENSO and the changes in climate system are identified by utilizing the newly defined PC2. Since the La Nina index (defined as the negative of NINO3 index) leads PC2 by about 11 months, it may be possible that the La Nina causes the warming to be interrupted. We also show that the cooling of the climate system closed tied to the heat penetration into the deep ocean, indicating the weakening the warming rate is due to the oceanic heat uptake. Finally, the global warming hiatus is characterized by the anomalous warming in Arctic region as well as the intensification of the trade wind in the equatorial Pacific.
ER –

NR – 193
TY – JOUR
TI – Linear and Nonlinear Trends of Extreme Temperatures in Korea
AU – Kim, Sang-Wook
AU – Song, Kanghyun
AU – Kim, Seo-Yeon
AU – Son, Seok-Woo
AU – Franzke, C.
JO – Atmosphere
VL – 24
IS – 3
SP – 379
EP – 390
PY – 2014
UR – http://www.dbpia.co.kr/Article/NODE02486406
AB – This study explores the long-term trends of surface air temperatures in 11 KMA stations over the period of 1960~2012. Both linear and nonlinear trends are examined for the 95^th, 50^th, and 5^th percentiles of daily maximum (T_max) and minimum temperatures (T_min) by using quantile regression method. It is found that in most stations linear trends of T_max and T_min are generally stronger in winter than in summer, and warming trend of the 5^th percentile temperature (cold extreme) is stronger than that of the 95^th percentile temperature (warm extreme) in both seasons. The nonlinear trends, which are evaluated by the second order polynomial fitting, show a strong nonlinearity in winter. Specifically, winter temperatures have increased until 2000s but slightly decreased afterward in all percentiles. This contrasts with the 95^th and 50t^h percentiles of summer T_min that show a decreasing trend until 1980s then an increasing trend. While this result is consistent with a seasonal dependence of the recent global warming hiatus, most of the nonlinear trends are statistically insignificant, making a quantitative attribution of nonlinear temperature trends challenging.
ER –

NR – 194
TY – JOUR
TI – Enhanced Responses of Sea Surface Temperature over Offshore China to Global Warming and Hiatus
AU – Tan, Hongjian
AU – Cai, Rongshuo
AU – Huang, Ronghui
PY – 2016
JO – Advances in Climate Change Research
VL – 12
IS – 6
SP – 500
EP – 507
DO – 10.12006/j.issn.1673-1719.2016.038
UR – http://www.climatechange.cn/CN/abstract/abstract9266.shtml
AB – In this study, we assessed and compared the sea surface temperature (SST) trends between offshore China and other sea regions of interest as well as global mean surface temperature based on four SST datasets. The results revealed an enhanced SST response over offshore China during different periods. During the accelerated global warming periods (1980s and 1990s), SST over offshore China shows faster rising trend than the global mean. The most pronounced warming area is located over the East China Sea, with the rising rate up to 0.60? per decade, which is 5 times faster than that of the global mean. While during the hiatus period (1998-2014), SST over offshore China exhibits significant cooling trend. The decadal variability of offshore China SST is closely linked to the Pacific Decadal Oscillation (PDO). The periods with rapid warming (cooling) over offshore China are consistent with the positive (negative) phase of PDO. PDO may affect SST over offshore China through the East Asian Monsoon and Kuroshio Current.
ER –

NR – 195
TY – JOUR
TI – Research on the global warming Hiatus
AU – Lin, Xiaopei
AU – Xu, Lixiao
AU – Li, Jianping
AU – Luo, Dehai
AU – Liu, Hailong
PY – 2016
JO – Advances in Earth Science
VL – 31
IS – 10
SP – 995
EP – 1000
DO – 10.11867/j.issn.1001-8166.2016.10.0995
UR – http://www.adearth.ac.cn/article/2016/1001-8166-31-10-995.html
AB – A global warming “hiatus” has been observed since the beginning of the 21st century despite the increase in heat-trapping greenhouse gases, challenging the current global warming studies. Focusing on the phenomena and mechanisms of the global warming “hiatus”, the National Key Research Program of China launched a project in July, 2016. The main research themes of this project cover: ?Revealing the spatial and temporal variability of the global warming hiatus, and quantifying the contributions of external forcing and internal (natural) variability, respectively; ?Revealing the role of the atmosphere in the global heat and energy redistribution under global warming hiatus; ?Revealing the role of the ocean in the global heat and energy redistribution under global warming hiatus; ?Investigating the predictability of the global warming hiatus. The key scientific issues to be resolved include: ?Identifying characteristics of the global warming hiatus and discerning the roles of decadal, multi-decadal oscillations; ?Revealing the role of ocean-atmosphere dynamical processes in the global redistribution of heat and energy; ?Understanding the predictability of the global warming hiatus. The research aims to predict the future development of the global warming hiatus, and to point out the possible impacts on China and other important areas, including “The Belt and Road” core area and the Polar Regions.
ER –

NR – 196
TY – JOUR
TI – Research Progress on Hiatus in The Process of Global Warming
AU – Chen, Xingrong
AU – Cai Yi
AU – Tan Jing
AU – Wang Lei
PY – 2014
JO – Advances in Earth Science
VL – 29
IS – 8
SP – 947
EP – 955
UR – http://www.adearth.ac.cn/article/2014/1001-8166-29-8-0947.html
AB – In the 21st century, global warming hiatus has become a new hotspot in the research of climate change. This paper introduces the research progress on this phenomenon in detail, especially the validation studies of hiatus, research on the influence of the radiation forcing and the natural variability of the climate system due to air?sea interaction, and then puts forward several puzzles that still need to be solved on current research of hiatus. The paper particularly introduces the international major view, which think that the main reason of the hiatus in this century is that the strengthened trade wind on the background of the PDO negative phase leads to the warm water “accumulation”? in the equatorial western Pacific while the cooling in equatorial eastern Pacific causes the heat transferred down to the deep ocean. Therefore, hiatus phenomenon does not mean the stop of global warming, but just the heat transportation to the deep ocean, which is another manifestation of global warming.
ER –

NR – 197
TY – JOUR
TI – A review of recent studies on global warming hiatus
AU – Song, Bin
AU – Zhi, Xie-Fei
AU – Hu, Yao-Xing
PY – 2015
JO – Transactions of Atmospheric Sciences
VL – 38
IS – 2
SP – 145
EP – 154
DO – 10.13878/j.cnki.dqkxxb.20150105002
UR – http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=njqxxyxb201502001
AB – Since the industrial revolution, the content of anthropogenic greenhouse gas is increasing. As a result, the global surface air temperature grows rapidly. However, the global surface air temperature has stalled since 1998, despite the greenhouse gas steadily increases. This paper reviewed the latest research progress on this phenomenon, especially the mechanism of the global warming hiatus. There are two main viewpoints on the mechanism, namely, the external forcing and natural variability. The former includes the influence of solar activity, volcanic aerosol particles, man-made aerosol particles and stratospheric water vapor forcing. Scientists in the opinion of natural variability hold the idea that the missing heat produced by human activity has entered the deep ocean, especially the layer below 700 m. They believe that the oceans play a key role in the global warming hiatus. There are two main ideas for that: Pacific Decadal Oscillation (PDO), especially the cooling in the eastern tropical Pacific, and the Atlantic Meridional Overturning Circulation (AMOC). The widely accepted idea on the mechanism of recent global warming hiatus is natural variability. The missing heat has entered the deep ocean. But it still remains controversial which ocean basin gain the missing heat.
ER –

NR – 198
TY – JOUR
TI – Evolution of Surface Temperature during Global Warming Hiatus Based on Observations and CMIP5 Simulations
AU – He, Jinhai
AU – Zhan, Fengxing
AU – Qi, Li
AU – Wang, Di
PY – 2016
JO – Chinese Journal of Atmospheric Sciences
VL – 40
IS – 1
SP – 33
EP – 45
DO – 10.3878/j.issn.1006-9895.1409.14217
UR – http://www.dqkxqk.ac.cn/dqkx/dqkx/ch/html/20160105.htm
AB – The rise in global surface temperature has significantly declined after 2000. In this study, the evolution of the surface temperature of the global land-mean and Eurasia middle-high latitudes during the global warming hiatus was analyzed based on CRU observations. Simulations and projections were also evaluated using the Coupled Model Intercomparison Project 5 (CMIP5). The results indicate that, in the global warming hiatus period, the trend of the global land-mean surface temperature is only 0.14? (10 a)-1, which is half that during 1976-1999. The trend is less than that before 2000 in nine of the 13 global land regions, and four of them show a decreasing trend. The Eurasia middle-high latitude region is the most interesting among all the regions. For 1976-1999, the Eurasia middle-high latitude region shows the largest warming among all the land regions and reaches 0.50? (10 a)-1. After 2000, the trend significantly declines to -0.17? (10 a)-1, the greatest cooling trend over land, globally, contributing 49.13% of the remarkable change in global land surface temperatures before and after 2000. Furthermore, the surface temperature of the Eurasia middle-high latitude region shows an opposite change in autumn and winter after 2000; the temperature of the former rises by 0.86? (10 a)-1, while the that of the latter decreases by 2.68? (10 a)-1. In CMIP5, only the simulation and projects in BCC-CSM1.1 under the RCP2.6 scenario and MRI-ESM1 under the RCP8.5 scenario reproduce the evolution of the global land-mean and Eurasia middle-high latitude surface temperature, as well as the opposite change between autumn and winter of the Eurasia middle-high latitude region, during the global warming hiatus. The temperature projection of the BCC-CSM1.1 under the RCP2.6 scenario for the Eurasia middle-high latitude remains flat, near 1.2?, after 2012, and jumps to 2? after 2020. The change in the MRI-ESM1’s projected temperature under the RCP8.5 scenario is close to zero before 2030; the temperature then rises remarkably, to ? (10 a)-1.
ER –

NR – 199
TY – JOUR
TI – Hiatus of global warming: A review
AU – Su, Jingzhi
AU – Wen, Min
AU – Ding, Yihui
AU – Gao, Yongqi
AU – Song, Yafang
PY – 2016
JO – Chinese Journal of Atmospheric Sciences
VL – 40
IS – 6
SP – 1143
EP – 1153
DO – 10.3878/j.issn.1006-9895.1512.15242
UR – http://www.dqkxqk.ac.cn/dqkx/ch/reader/create_pdf.aspx?file_no=20160604&flag=1&journal_id=dqkx
ER –

NR – 200
TY – JOUR
TI – Debate on Global Warming “Hiatus”
AU – Zhao, Zongci
AU – Luo, Yong
AU – Huang, Jianbin
PY – 2016
JO – Climate Change Research
VL – 12
IS – 6
SP – 571
EP – 574
DO – 10.12006/j.issn.1673-1719.2016.055
UR – http://www.climatechange.cn/CN/10.12006/j.issn.1673-1719.2016.055
ER –

NR – 201
TY – JOUR
TI – Climate change science and sustainable development
AU – Qin, Dahe
PY – 2014
JO – Progress in Geography
VL – 33
IS – 7
SP – 874
EP – 883
DO – 10.11820/dlkxjz.2014.07.002
UR – http://www.progressingeography.com/CN/abstract/abstract14634.shtml
AB – Since the Fourth Assessment Report (AR4) was released by the Intergovernmental Panel on Climate Change (IPCC) in 2007, new observations have further proved that the warming of the global climate system is unequivocal. Each of the last three successive decades before 2012 has been successively warmer at global mean surface temperature than any preceding decade since 1850. 1983-2012 was likely the warmest 30-year period of the last 1400 years. From 1998 to 2012, the rate of warming of the global land surface slowed down, but it did not reflect the long-term trends in climate change. The ocean has warmed, and the upper 75 m of the ocean warmed by more than 0.11? per decade since 1970. Over the period of 1971 to 2010, 93% of the net energy increase in the Earth’s climate system was stored in the oceans. The rate of global mean sea level rise has accelerated, which was up to 3.2 mm yr-1 between 1993 and 2010. Anthropogenic global ocean carbon stocks were likely to have increased and caused acidification of the ocean surface water. Since 1971, the glaciers and the Greenland and Antarctic ice sheets have been losing mass. Since 1979, the Arctic sea ice extent deceased at 3.5% to 4.1% per decade, and the Antarctic sea ice extent in the same period increased by 1.2% to 1.8% per decade. The extent of the Northern Hemisphere snow cover has decreased. Since the early 1980s, the permafrost temperatures have increased in most regions. Human influence has been detected in the warming of the atmosphere and the ocean, changes in the water cycle, reductions in snow and ice, global mean sea level rise, and changes in climate extremes. The largest contribution to the increase in the anthropogenic radiative forcing was by the increase in the atmospheric concentration of CO2 since 1750. It led to more than half of global warming since the 1950s (with 95 % confidence). It is predicted using Coupled Model Intercomparison Project Phase 5 (CMIP5) and Representative Concentration Pathways (RCPs) that the global mean surface temperature will continue to rise for the end of this century, the frequency of extreme events such as heat waves and heavy precipitation will increase, and precipitation will present a trend of “the dry becomes drier, the wet becomes wetter”. The temperature of the upper ocean will increase by 0.6 to 2.0? compared to the period of 1986 to 2005, heat will penetrate from the surface to the deep ocean which will affect ocean circulation, and sea level will rise by 0.26 to 0.82 m in 2100. Cryosphere will continue to warm. To control global warming, humans need to reduce the greenhouse gas emissions. If the increase in temperature is higher than 2? than before industrialization, the mean annual economic losses worldwide will reach 0.2% to 2.0% of income, and cause large-scale irreversible effects, including death, disease, food insecurity, inland flooding and water logging, and rural drinking water and irrigation difficulties that affect human security. If taking prompt actions, however, it is still possible to limit the increase in temperature within 2?. To curb the gradually out-of-control global warming and achieve the goal of sustainable development of the human society, global efforts to reduce emissions are needed.
ER –

NR – 202
TY – JOUR
TI – Temperature mutation and globe warming stagnate study in typical area of Yellow River basin in recently 60years
AU – Huang, Xing
AU – Ma, Long
AU – Liu, Ting-xi
AU – Wang, Jing-ru
AU – Liu, Dan-hui
AU – Li, Hong-yu
PY – 2016
JO – China Environmental Science
VL – 36
IS – 11
SP – 3253
EP – 3262
UR – http://manu36.magtech.com.cn/Jweb_zghjkx/CN/abstract/abstract14853.shtml
AB – The part of Yellow River in Inner Mongolia was chosen as a typical area of Yellow River Basin. The regional annual average maximum temperature (AMaxT), annual average minimum temperature (AMinT) and annual average temperature (AvT) from 1951 to 2012 were selected and analyzed by Mann-Kendall method. The temperature variations before and after the mutation and the warming stagnate following the mutation were also discussed. Annual (or seasonal) AMinT mutation happened first on 1977 to 1987. Then the AvT and AMaxT mutation happened on 1978 to 1993 and 1978 to 1994, respectively. The mutation period of average autumn and winter temperature were same as AMaxT. The earliest intra-annual mutation was winter (1977 to 1978), and the latest was summer (1987 to 1994). The winter and AMaxT had more variations than summer and AMinT. The increase ratio or AMinT was 0.231~0.604?/10a which have the most contribution. All the annual (or seasonal) temperatures had a warming stagnate from 1997 to 2007 after the mutation, successively. The stagnate occurred in spring and not stagnate occurred in summer. Mostly annual and seasonal temperature stagnate happened later than the global period which winter firstly, then autumn, the AvT was the last one (on 2007). The AMaxT increase rate was lower in the period of after mutation and before stagnate. However, the decrease rate of AMaxT if faster after stagnate. The AMinT was on the contrary. This indicates that the AMinT was sensitive to temperature increase and the AMaxT was sensitive to the temperature decrease. In seasonal, the spring AMaxT increase rate is higher from mutation to stagnate, and the spring AMinT decrease rate was the fastest after the temperature stagnate which is -0.324?/a.
ER –

NR – 203
TY – JOUR
TI – Recent global-warming “hiatus” and its implications on the measures to be taken against global warming
AU – Junichi, Tsuitii
PY – 2014
JO – Energy and power
VL – 64
IS – 283
SP – 80
EP – 86
UR – http://ci.nii.ac.jp/naid/40020266117/
ER –

NR – 204
TY – JOUR
TI – Surface Temperature and Precipitation Variation of Pastoral Transitional Zone in Northern China during 1964-2013
AU – Zhao, Wei
AU – Wei, Zhigang
AU – Zheng, Zhiyuan
AU – Dong, Wenjie
PY – 2016
JO – Plateau Meteorology
VL – 35
IS – 4
SP – 979
EP – 988
DO – 10.7522/j.issn.1000-0534.2015.00079
UR – http://html.rhhz.net/gyqx/html/20160413.htm
AB – This study analyzed the spatial-temporal change of historical temperature and precipitation in pastoral transitional zone in Northern China, based on observational temperature and precipitation grid datasets during 1964-2013 from Chinese Meteorology Administration (CMA). The climate division was made using rotated empirical orthogonal function (REOF) in the meantime. The result shows that: (1) The whole pastoral transitional zone in Northern China can be divided into 4 regions which can be simply named the west region, the central region, the southern section of the east region, and the northern section of the east region, respectively. (2) In general, the pastoral transitional zone in Northern China had experienced a significant warming during 1964-2013 which was mainly attributed to the warming of winter and larger increase of minimum temperature rather than the increase of maximum temperature. The pastoral transitional zone in Northern China had also experienced a slightly decrease of precipitation (13 mm less during 1964 -2013), and it was largely because the summer precipitation had declined the most in this period. (3) Focused on sub-regions, the temperature of the central region in pastoral transitional zone increased the most in the period of 1964-2013 among 4 sub-regions. As for the precipitation, annual precipitation in western north region decreased in the last 50 years mostly because of the decrease of spring precipitation in local. Meanwhile, the annual precipitation in central region and the southern section of the east region had decreased as well, but differently, it can be mainly attributed to the summer precipitation’s decline. Moreover, the annual precipitation increased in the northern section of the east region, and the spring precipitation contributed it the most. (4) The pastoral transitional zone in Northern China has experienced a warming hiatus resembling to the global warming hiatus since late 1990s, only the temperature has declined more, meaning that the declining trend of temperature in pastoral transitional zone is more obvious.
ER –

NR – 205
TY – JOUR
TI – Characteristics of Climate Change over the Tibetan Plateau Under the Global Warming During 1979-2014
AU – Duan, Anmin
AU – Xiao, Zhixiang
AU – Wu, Guoxiong
PY – 2016
JO – Advances in Climate Change Research
VL – 12
IS – 5
SP – 374
EP – 381
DO – 10.12006/j.issn.1673-1719.2016.039
UR – http://www.climatechange.cn/CN/Y2016/V12/I5/374
AB – Global warming has been a hot issue during recent decades, while the global warming hiatus since 1998 was detected as documented by many papers, meanwhile the Tibetan Plateau (TP) experiencing a rapid warming process. Based on previous studies, this paper mainly reviews the TP climate change under the global warming in four aspects: temperature, snow cover, precipitation and atmospheric apparent heat source, and points out that the accelerated warming over the TP results in the retreat of snow cover accompanied by the increase of precipitation. Though the TP heat source has been declined in recent decades whether based on observation or reanalysis datasets, it shows large uncertainties.
ER –

NR – 206
TY – JOUR
TI – CMIP5 climate model simulates the empirical study of global temperature change from 1850 to 2014
AU – Meng, Wei
AU – Fangli, Qiao
PY – 2016
JO – SCIENTIA SINICA Terrae
VL – 46
IS – 12
SP – 1675
EP – 1688
DO – 10.1360/N072015-00465
UR – http://engine.scichina.com/publisher/scp/journal/SSTe/46/12/10.1360/N072015-00465
ER –

NR – 207
TY – JOUR
T1 – The Community Earth System Model (CESM) Large Ensemble Project: A Community Resource for Studying Climate Change in the Presence of Internal Climate Variability
AU – Kay, J. E.
AU – Deser, C.
AU – Phillips, A.
AU – Mai, A.
AU – Hannay, C.
AU – Strand, G.
AU – Arblaster, J. M.
AU – Bates, S. C.
AU – Danabasoglu, G.
AU – Edwards, J.
AU – Holland, M.
AU – Kushner, P.
AU – Lamarque, J.-F.
AU – Lawrence, D.
AU – Lindsay, K.
AU – Middleton, A.
AU – Munoz, E.
AU – Neale, R.
AU – Oleson, K.
AU – Polvani, L.
AU – Vertenstein, M.
PY – 2014
DO – 10.1175/BAMS-D-13-00255.1
JF – Bulletin of the American Meteorological Society
SP – 1333
EP – 1349
VL – 96
IS – 8
AB – While internal climate variability is known to affect climate projections, its influence is often underappreciated and confused with model error. Why? In general, modeling centers contribute a small number of realizations to international climate model assessments [e.g., phase 5 of the Coupled Model Intercomparison Project (CMIP5)]. As a result, model error and internal climate variability are difficult, and at times impossible, to disentangle. In response, the Community Earth System Model (CESM) community designed the CESM Large Ensemble (CESM-LE) with the explicit goal of enabling assessment of climate change in the presence of internal climate variability. All CESM-LE simulations use a single CMIP5 model (CESM with the Community Atmosphere Model, version 5). The core simulations replay the twenty to twenty-first century (1920?2100) 30 times under historical and representative concentration pathway 8.5 external forcing with small initial condition differences. Two companion 1000+-yr-long preindustrial control simulations (fully coupled, prognostic atmosphere and land only) allow assessment of internal climate variability in the absence of climate change. Comprehensive outputs, including many daily fields, are available as single-variable time series on the Earth System Grid for anyone to use. Early results demonstrate the substantial influence of internal climate variability on twentieth- to twenty-first-century climate trajectories. Global warming hiatus decades occur, similar to those recently observed. Internal climate variability alone can produce projection spread comparable to that in CMIP5. Scientists and stakeholders can use CESM-LE outputs to help interpret the observational record, to understand projection spread and to plan for a range of possible futures influenced by both internal climate variability and forced climate change.
UR – https://doi.org/10.1175/BAMS-D-13-00255.1
ER –

NR – 208
TY – JOUR
AU – Meehl, Gerald A.
AU – Teng, Haiyan
TI – Case studies for initialized decadal hindcasts and predictions for the Pacific region
JO – Geophysical Research Letters
VL – 39
IS – 22
UR – http://dx.doi.org/10.1029/2012GL053423
DO – 10.1029/2012GL053423
PY – 2012
AB – Case studies involving notable past decadal climate variability are analyzed for the mid-1970s climate shift, when the tropical Pacific warmed over a decade and globally averaged temperature rapidly increased, and the early 2000s hiatus when the tropical Pacific cooled over a decade and global temperatures warmed little. Ten year hindcasts following the CMIP5 decadal climate prediction experiment design are analyzed for those two periods using two different initialization techniques in a global coupled climate model, the CCSM4. There is additional skill in the initialized hindcasts for surface temperature patterns over the Pacific region for those two case studies over and above that in free-running historical simulations with the same model. A 30 year hindcast also shows added skill over the Pacific compared to the historical simulations. A 30 year prediction from the initialized model simulations shows less global warming for the 2016–2035 period than the free-running model projection for that same time period.
ER –

NR – 209
TY – JOUR
T1 – Anthropogenic CO2 warming challenged by 60-yearcycle
AU – Gervais, François
JO – Earth-Science Reviews
VL – 155
SP – 129
EP – 135
PY – 2016
DO – https://doi.org/10.1016/j.earscirev.2016.02.005
UR – http://www.sciencedirect.com/science/article/pii/S0012825216300277
AB – Time series of sea-level rise are fitted by a sinusoid of period ~60years, confirming the cycle reported for the global mean temperature of the earth. This cycle appears in phase with the Atlantic Multidecadal Oscillation (AMO). The last maximum of the sinusoid coincides with the temperature plateau observed since the end of the 20th century. The onset of declining phase of AMO, the recent excess of the global sea ice area anomaly and the negative slope of global mean temperature measured by satellite from 2002 to 2015, all these indicators sign for the onset of the declining phase of the 60-yearcycle. Once this cycle is subtracted from observations, the transient climate response is revised downwards consistent with latest observations, with latest evaluations based on atmospheric infrared absorption and with a general tendency of published climate sensitivity. The enhancement of the amplitude of the CO2 seasonal oscillations which is found up to 71% faster than the atmospheric CO2 increase, focus on earth greening and benefit for crops yields of the supplementary photosynthesis, further minimizing the consequences of the tiny anthropogenic contribution to warming.
ER –

NR – 210
TY – JOUR
AU – Lorentzen, Torbjørn
PY – 2015
TI – A statistical analysis of sea temperature data
JO – Theoretical and Applied Climatology
SP – 585
EP – 610
VL – 119
IS – 3
AB – The paper analyzes sea temperature series measured at two geographical locations along the coast of Norway. We address the question whether the series are stable over the sample period 1936–2012 and whether we can measure any signal of climate change in the regional data. We use nonstandard supF, OLS-based CUSUM, RE, and Chow tests in combination with the Bai-Perron’s structural break test to identify potential changes in the temperature. The augmented Dickey-Fuller, the KPSS, and the nonparametric Phillips-Perron tests are in addition applied in the evaluation of the stochastic properties of the series. The analysis indicates that both series undergo similar structural instabilities in the form of small shifts in the temperature level. The temperature at Lista (58° 06′ N, 06° 38′ E) shifts downward about 1962 while the Skrova series (68° 12′ N, 14° 10′ E) shifts to a lower level about 1977. Both series shift upward about 1987, and after a period of increasing temperature, both series start leveling off about the turn of the millennium. The series have no significant stochastic or deterministic trend. The analysis indicates that the mean temperature has moved upward in decadal, small steps since the 1980s. The result is in accordance with recent analyses of sea temperatures in the North Atlantic. The findings are also related to the so-called hiatus phenomenon where natural variation in climate can mask global warming processes. The paper contributes to the discussion of applying objective methods in measuring climate change.
UR – https://doi.org/10.1007/s00704-014-1119-x
DO – 10.1007/s00704-014-1119-x
ER –

NR – 211
TY – JOUR
AU – Li, Qingxiang
AU – Yang, Su
AU – Xu, Wenhui
AU – Wang, Xiaolan L.
AU – Jones, Phil
AU – Parker, David
AU – Zhou, Liming
AU – Feng, Yang
AU – Gao, Yun
TI – China experiencing the recent warming hiatus
JO – Geophysical Research Letters
VL – 42
IS – 3
UR – http://dx.doi.org/10.1002/2014GL062773
DO – 10.1002/2014GL062773
SP – 889
EP – 898
PY – 2015
AB – Based on the homogenized data set, we analyze changes in mean temperature and some extreme temperature indices over China since 1961 and especially during the recent warming hiatus period (1998–2012) in a global average context. The result shows that the decrease of annual mean maximum has contributed most to the decreases in overall mean temperature and in diurnal temperature range (DTR) during the warming hiatus period. In most parts of China except the southwest, the summer mean maximum temperature (TxS) shows the largest increase, while the winter mean minimum temperature (TnW) indicates slight cooling trends. These changes have augmented the seasonal cycle and increased the likelihood of extreme warm and cold events. Further analyses reveal that the increases in TxS are significantly correlated with concurrent increases in solar radiation. In southwest China, the annual mean temperature, TxS, TnW, and DTR increased during 1998–2012, possibly related to increased dryness in this region during the hiatus period.
ER –

NR – 212
TY – JOUR
AU – Ueda, Hiroaki
AU – Kamae, Youichi
AU – Hayasaki, Masamitsu
AU – Kitoh, Akio
AU – Watanabe, Shigeru
AU – Miki, Yurisa
AU – Kumai, Atsuki
TI – Combined effects of recent Pacific cooling and Indian Ocean warming on the Asian monsoon
JA – Nature Communications
PY – 2015
VL – 6
SP – 8854
UR – http://dx.doi.org/10.1038/ncomms9854
DO – 10.1038/ncomms9854
AB – Recent research indicates that the cooling trend in the tropical Pacific Ocean over the past 15 years underlies the contemporaneous hiatus in global mean temperature increase. During the hiatus, the tropical Pacific Ocean displays a La Niña-like cooling pattern while sea surface temperature (SST) in the Indian Ocean has continued to increase. This SST pattern differs from the well-known La Niña-induced basin-wide cooling across the Indian Ocean on the interannual timescale. Here, based on model experiments, we show that the SST pattern during the hiatus explains pronounced regional anomalies of rainfall in the Asian monsoon region and thermodynamic effects due to specific humidity change are secondary. Specifically, Indo-Pacific SST anomalies cause convection to intensify over the tropical western Pacific, which in turn suppresses rainfall in mid-latitude East Asia through atmospheric teleconnection. Overall, the tropical Pacific SST effect opposes and is greater than the Indian Ocean SST effect.
ER –

NR – 213
TY – JOUR
AU – Saffioti, Claudio
AU – Fischer, Erich M.
AU – Knutti, Reto
TI – Contributions of atmospheric circulation variability and data coverage bias to the warming hiatus
JO – Geophysical Research Letters
VL – 42
IS – 7
UR – http://dx.doi.org/10.1002/2015GL063091
DO – 10.1002/2015GL063091
SP – 2385
EP – 2391
PY – 2015
AB – The warming hiatus shows a strong seasonal and geographical asymmetry, with cooling in the Northern Hemisphere winter, especially over land, and warming elsewhere and in the other seasons. We show that the characteristics of the Northern Hemisphere winter cooling in 1998–2012 can mostly be explained by missing observations and by internal variability in the atmospheric circulation of the Northern Hemisphere extratropics. Estimates of the annual and seasonal temperature trends in 1998–2012 obtained by considering the concurrent effects of unforced natural variability and of coverage bias are much closer to the corresponding long-term trends. Reanalyses suggest that the coverage bias was exceptionally pronounced during recent years and that an area of strong warming was missed due to the incomplete observational coverage. Coupled Model Intercomparison Project Phase 5 climate models indicate that trends in atmospheric circulation during the hiatus period did not occur as a response to anthropogenic forcing.
ER –

NR – 214
TY – JOUR
T1 – Clarifying the Roles of Greenhouse Gases and ENSO in Recent Global Warming through Their Prediction Performance
AU – Triacca, Umberto
AU – Pasini, Antonello
AU – Attanasio, Alessandro
AU – Giovannelli, Alessandro
AU – Lippi, Marco
PY – 2014
DO – 10.1175/JCLI-D-13-00784.1
JF – Journal of Climate
SP – 7903
EP – 7910
VL – 27
IS – 20
AB – It is well known that natural external forcings and decadal-to-millennial variability drove changes in the climate system throughout the Holocene. Regarding recent times, attribution studies have shown that greenhouse gases (GHGs) determined the trend of temperature (T) in the last half century, while circulation patterns contributed to modify its interannual, decadal, or multidecadal behavior over this period. Here temperature predictions based on vector autoregressive models (VARs) have been used to study the influence of GHGs and El Niño?Southern Oscillation (ENSO) on recent temperature behavior. It is found that in the last decades of steep temperature increase, ENSO shows just a very short-range influence on T, while GHGs are dominant for each forecast horizon. Conversely and quite surprisingly, in the previous quasi-stationary period the influences of GHGs and ENSO are comparable, even at longer range. Therefore, if the recent hiatus in global temperatures should persist into the near future, an enhancement of the role of ENSO can be expected. Finally, the predictive ability of GHGs is more evident in the Southern Hemisphere, where the temperature series is smoother.
UR – https://doi.org/10.1175/JCLI-D-13-00784.1
ER –

NR – 215
TY – JOUR
T1 – The global warming hiatus’s irrelevance
JO – Science
SP – 1482
LP – 1483
DO – 10.1126/science.350.6267.1482-d
VL – 350
IS – 6267
AU – Wehner, Michael F.
AU – Easterling, David R.
PY – 2015
UR – http://science.sciencemag.org/content/350/6267/1482.4.abstract
ER –

NR – 216
TY – JOUR
AU – Quirk, Tom
PY – 2012
TI – Did the global temperature trend change at the end of the 1990s?
JO – Asia-Pacific Journal of Atmospheric Sciences
SP – 339
EP – 344
VL – 48
IS – 4
AB – The apparent leveling of the global temperature time series at the end of the 1990s may represent a break in the upward trend. A study of the time series measurements for temperature, carbon dioxide, humidity and methane shows changes coincident with phase changes of the Atlantic and Pacific Decadal Oscillations. There are changes in carbon dioxide, humidity and methane measurement series in 2000. If these changes mark a phase change of the Pacific Decadal Oscillation then it might explain the global temperature behavior.
UR – https://doi.org/10.1007/s13143-012-0032-4
DO – 10.1007/s13143-012-0032-4
ER –

NR – 217
TY – JOUR
TI – Discussion of the case of the missing heat
AU – Parker, Albert
PY – 2014
JO – Nonlinear Engineering
VL – 3
IS – 4
SP – 247
EP – 253
DO – 10.1515/nleng-2014-0011
UR – http://www.degruyter.com/view/j/nleng.ahead-of-print/nleng-2014-0011/nleng-2014-0011.xml
AB – The sea level projection of a 1 meter rise for the 21st century depends on climate models that have projected a given amount of anthropogenic warming during the same period. However, these same climate models predicted a warming also from 2000 to 2014, which has not been seen in the global surface temperature. Researchers have proposed several solutions such as the fact that the “missing heat” was accumulated in the deep ocean. However, no evidences of a sufficient warming of the deep oceans have been observed. Other arguments has been proposed as well and found unsatisfactory. There is the opportunity that the “heat” is not “real” but “missing” or “hiding” somewhere. If the climate model projected “heat” that simply does not exist in reality in the first place, consequently the models overestimate the anthropogenicwarming and also the sea level projections for the 21st century are overestimated.
ER –

NR – 218
TY – JOUR
T1 – Expected halt in the current global warming trend?
AU – Njau, Ernest C.
JO – Renewable Energy
VL – 30
IS – 5
SP – 743
EP – 752
PY – 2005
DO – https://doi.org/10.1016/j.renene.2004.07.011
UR – http://www.sciencedirect.com/science/article/pii/S0960148104002939
AB – The variation patterns of global temperature were considerably turbulent from about 1870 up to 1940. Then just after 1940 these patterns underwent a sunspot-related change and adopted to relatively less turbulent variability. It is established here that these global temperature patterns are currently in the process of undergoing a sunspot-related change from the post-1940 relatively less turbulent variability back into relatively more turbulent variability. This apparently imminent state of more turbulent variability is expected to stop and at least slightly reverse the global warming trend, which has been going on since about 1965. Besides, it is shown separately that the mean of ‘global mean temperature variations’ reaches the next peak at about the year 2005 after which it will expectedly be on a decreasing trend. Finally, it is shown that, contrary to projections made in the Third IPCC Assessment Report, Greenland is currently in an ongoing cooling trend which is expected to last up to at least the year 2035.
ER –

NR – 219
TY – JOUR
TI – Why global warming went missing since the year 2000
AU – Parker, Albert
PY – 2013
JO – Nonlinear Engineering
VL – 2
IS – 3-4
SP – 129
EP – 135
DO – 10.1515/nleng-2013-0017
UR – http://www.degruyter.com/view/j/nleng.2013.2.issue-3-4/nleng-2013-0017/nleng-2013-0017.xml
AB – Over the period January 2004 to present, the seas have experienced the lack of any warming, as finally properly measured in the ARGO project where a global array of more than 3,600 free-drifting profiling floats has measured the temperature of the upper 2000 m of the sea as it was not possible before. The warming of the seas has been a negligible 1.1*10-3 °C/year on average over the layer 0 – 2000 dbar below the accuracy of the measure. Over the period January 2000 to present, the measured land and sea temperatures of the less reliable GISS, NCDC and HADCRUT4 data sets have shown a small warming of 4.2*10-3 °C/year on average. Same period, the climate models propose for the land and sea temperatures an unrealistic warming of 20.5*10-3 °C/year (average of CMIP3) and 18.2*10-3 °C/year (average of the CMIP5). The “inconvenient truth” is that climate models are predicting a warming when there is no warming rather than simply overestimating the warming as discussed so far. The paper presents the failed validation of the climate models since their introduction and suggests the reasons of their failure in the overrated effect of the changed composition of the atmosphere and the neglected natural oscillations.
ER –

NR – 220
TY – JOUR
TI – Key Issues on Debating about the Global Warming
AU – Wang, Shaowu
AU – Ge, Quansheng
AU – Wang, Fang
AU – Wen, Xinyu
AU – Huang, Jianbin
PY – 2010
JO – Advances in Earth Science
VL – 6
UR – http://en.cnki.com.cn/Article_en/CJFDTOTAL-DXJZ201006015.htm
AB – Key issues on debating about global warming are reviewed:?Does the global warming pause? The answer is not sure.The HadCRUT3 data show that the temperature during 1999-2008 increased only a little(0.07?/10a),but this decade is still the most warmest one among the last 30 years.However,the data from NASA GISS indicate that the temperature increased in the same period is higher(0.19?/10a).Thus,global surface temperature in recent years oscillates on a warm level.However,natural variability needs to be taken into consideration.?Does the global warming be caused fully by anthropogenic factors? The answer is no.ENSO,solar activity,volcanism,and thermohaline circulation can also exert impact in some extent on climate change,though the morden global warming may be mostly attributed to the increasing of greenhouse effect.However,the natural factors may sometimes overwhelm the anthropogenic effect in the interannual to interdecadal time scale.Specially,the solar activity factor should be given more attention.?Does the impact of global warming become more evident recently? The answer is yes.New observational datas indicate that the melting speed of glaciers and ice caps and rising speed of sea level in recent years have exceeded the related projections by IPCC 4th Assessment Report.Accordingly,the updated projection of the future sea level also increases.
ER –

NR – 221
TY – JOUR
TI – Mechanisms for the hiatus in global warming
AU – Tung, Ka-Kit
AU – Zhang, Rong
AU – Trenberth, Kevin E.
PY – 2014
JO – Engineering Sciences
VL – 2
DO – 10.3969/j.issn.1672-4178.2014.02.007
UR – http://d.wanfangdata.com.cn/periodical_zggckx-e201402007.aspx
AB – The observed global mean temperature is the highest on record for the past decade but has plateaued to form an apparent“hiatus”in global temperature rise,with an almost zero short-term trend. Several speakers presented results on the hiatus and suggested possible mechanisms.
ER –

NR – 222
TY – JOUR
TI – On the definition and identifiability of the alleged “hiatus” in global warming
AU – Lewandowsky, Stephan
AU – Risbey, James S.
AU – Oreskes, Naomi
JF – Scientific Reports
PY – 2015
VL – 5
SP – 16784
UR – http://dx.doi.org/10.1038/srep16784
DO – 10.1038/srep16784
AB – Recent public debate and the scientific literature have frequently cited a “pause” or “hiatus” in global warming. Yet, multiple sources of evidence show that climate change continues unabated, raising questions about the status of the “hiatus”. To examine whether the notion of a “hiatus” is justified by the available data, we first document that there are multiple definitions of the “hiatus” in the literature, with its presumed onset spanning a decade. For each of these definitions we compare the associated temperature trend against trends of equivalent length in the entire record of modern global warming. The analysis shows that the “hiatus” trends are encompassed within the overall distribution of observed trends. We next assess the magnitude and significance of all possible trends up to 25 years duration looking backwards from each year over the past 30 years. At every year during the past 30 years, the immediately preceding warming trend was always significant when 17 years (or more) were included in the calculation, alleged “hiatus” periods notwithstanding. If current definitions of the “pause” used in the literature are applied to the historical record, then the climate system “paused” for more than 1/3 of the period during which temperatures rose 0.6?K.
ER –

NR – 223
TY – JOUR
AU – Lempereur, Morine
AU – Limousin, Jean-Marc
AU – Guibal, Frédéric
AU – Ourcival, Jean-Marc
AU – Rambal, Serge
AU – Ruffault, Julien
AU – Mouillot, Florent
TI – Recent climate hiatus revealed dual control by temperature and drought on the stem growth of Mediterranean Quercus ilex
JO – Global Change Biology
JA – Glob Change Biol
VL – 23
IS – 1
UR – http://dx.doi.org/10.1111/gcb.13495
DO – 10.1111/gcb.13495
SP – 42
EP – 55
PY – 2017
AB – A better understanding of stem growth phenology and its climate drivers would improve projections of the impact of climate change on forest productivity. Under a Mediterranean climate, tree growth is primarily limited by soil water availability during summer, but cold temperatures in winter also prevent tree growth in evergreen forests. In the widespread Mediterranean evergreen tree species Quercus ilex, the duration of stem growth has been shown to predict annual stem increment, and to be limited by winter temperatures on the one hand, and by the summer drought onset on the other hand. We tested how these climatic controls of Q. ilex growth varied with recent climate change by correlating a 40-year tree ring record and a 30-year annual diameter inventory against winter temperature, spring precipitation, and simulated growth duration. Our results showed that growth duration was the best predictor of annual tree growth. We predicted that recent climate changes have resulted in earlier growth onset (-10 days) due to winter warming and earlier growth cessation (-26 days) due to earlier drought onset. These climatic trends partly offset one another, as we observed no significant trend of change in tree growth between 1968 and 2008. A moving-window correlation analysis revealed that in the past, Q. ilex growth was only correlated with water availability, but that since the 2000s, growth suddenly became correlated with winter temperature in addition to spring drought. This change in the climate–growth correlations matches the start of the recent atmospheric warming pause also known as the ‘climate hiatus’. The duration of growth of Q. ilex is thus shortened because winter warming has stopped compensating for increasing drought in the last decade. Decoupled trends in precipitation and temperature, a neglected aspect of climate change, might reduce forest productivity through phenological constraints and have more consequences than climate warming alone.
ER –

NR – 224
TY – JOUR
T1 – Briefing: How do we know the globe has warmed? What do we know about why?
AU – Thorne, Peter
PY – 2015
JF – Proceedings of the Institution of Civil Engineers – Forensic Engineering
VL – 168
IS – 2
SP – 58
EP – 64
DO – 10.1680/feng.15.00003
UR – https://www.icevirtuallibrary.com/doi/abs/10.1680/feng.15.00003
AB – This briefing outlines the evidence from instrumental records that leads to an unequivocal finding that the world has warmed. It then goes on to address the underlying causes, showing that only through invoking the effects of humans can the last 50 years be adequately explained. Finally, it addresses the recent hiatus/pause in warming of global surface temperatures and the implications thereof.
UR – https://doi.org/10.1680/feng.15.00003
ER –

NR – 225
TY – JOUR
TI – Characteristics of the Trends in the Global Tropopause Estimated From COSMIC Radio Occultation Data
AU – P. Gao
AU – X. Xu
AU – X. Zhang
PY – 2015
JO – IEEE Transactions on Geoscience and Remote Sensing
VL – 53
IS – 12
SP – 6813
EP – 6822
DO – 10.1109/TGRS.2015.2449338
UR – https://ieeexplore.ieee.org/abstract/document/7156128/
AB – This paper discusses the variabilities and trends in the global tropopause based on the gridded monthly mean Global Positioning System radio occultation data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission during July 2006-February 2014. We find that the tropopause height can reflect El Niño-Southern Oscillation (ENSO) events. The correlation coefficient between global tropopause height anomalies and the Niño 3.4 sea surface temperature index is 0.53, with a maximum correlation coefficient of 0.8 at a lag of three months. We present first the detailed investigations about the spatial distribution of trends in tropopause parameters in each 10° × 5° longitude-latitude grid cell over the globe and find that the rates of change in the tropopause parameters during this time period are high in some particular regions such as the Southern Indian Ocean, Antarctica, Western Europe, North Pacific, and the east coast of North America. An analysis of global monthly means of the tropopause parameters indicates a global tropopause height increase of 0.03 ± 2.36 m/year during 2006-2014, with a corresponding temperature increase of 0.020 ± 0.008°C/year, and a pressure increase of 0.11 ± 0.059 hPa/year. The upward trend of tropopause height is significantly weaker than that in the past years, which might be attributed to the expected stratospheric ozone recovery associated with the Montreal Protocol, the global warming slowdown, and the abnormal global climate change in recent years. The trends of the tropopause parameters are the most significant over the Southern Indian Ocean and Antarctica during September/October/November, which could be due to the stratospheric ozone recovery.
ER –