AGW Observer

Observations of anthropogenic global warming

Archive for October, 2012

New research from last week 43/2012

Posted by Ari Jokimäki on October 29, 2012

Last week I was on the road for few days, which resulted in rather limited collection on papers in the main section of this week’s post as I ended up putting many of the papers to the other papers section (which takes considerably less effort than creating a main section entry and making related Twitter and Facebook posts). So I expect that in coming weeks the main section grows back to normal size. That being said, now that the other papers section has been with us for a few weeks, I would like to know if you prefer lot of papers in the main section or lot of papers in other papers section or both. While we are at it, go ahead and make all kinds of improvement suggestions if you have them. If I’m in a good mood, I might even take a look at some of them…


Climate sensitivity increases by 23% between the first and third CO2 doublings in a model study

Climate feedbacks in CCSM3 under changing CO2 forcing. Part II: Variation of climate feedbacks and sensitivity with forcing – Jonko et al. (2012)

Abstract: “Are equilibrium climate sensitivity and the associated radiative feedbacks a constant property of the climate system, or do they change with forcing magnitude and base climate? Using the radiative kernel technique, feedbacks and climate sensitivity are evaluated in a fully coupled general circulation model (GCM) for three successive doublings of carbon dioxide starting from present day concentrations. Climate sensitivity increases by 23% between the first and third CO2 doublings. Increases in the positive water vapor and cloud feedbacks are partially balanced by a decrease in the positive surface albedo feedback and an increase in the negative lapse rate feedback. Feedbacks can be decomposed into a radiative flux change and a climate variable response to temperature change. The changes in water vapor and Planck feedbacks are due largely to changes in the radiative response with climate state. Higher concentrations of greenhouse gases and higher temperatures lead to more absorption and emission of longwave radiation. Changes in cloud feedbacks are dominated by the climate response to temperature change, while the lapse rate and albedo feedbacks combine elements of both. Simulations with a slab ocean model (SOM) version of the GCM are used to verify whether a SOM-GCM accurately reproduces the behavior of the fully coupled model. Although feedbacks differ in magnitude between model configurations (with differences as large as those between CO2 doublings for some feedbacks), changes in feedbacks between CO2 doublings are consistent in sign and magnitude in the SOM-GCM and the fully coupled model.”

Citation: Alexandra K. Jonko and Karen M. Shell, Benjamin M. Sanderson and Gokhan Danabasoglu, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00479.1.


Global heatwaves have increased in frequency, intensity and duration

Increasing frequency, intensity and duration of observed global heatwaves and warm spells – Perkins et al. (2012)

Abstract: “Using the latest HadGHCND daily temperature dataset, global trends in observed summertime heatwaves and annually calculated warm spells for 1950–2011 are analysed via a multi-index, multi-aspect framework. Three indices that separately focus on maximum temperature (TX90pct), minimum temperature (TN90pct) and average temperature (EHF) were studied with respect to five characteristics of event intensity, frequency and duration. Despite which index is employed, increases in heatwave/warm spell intensity, frequency and duration are found. Furthermore, TX90pct and TN90pct trends are larger and exhibit more significance for warm spells, implying that non-summer events are driving annual trends over some regions. Larger increases in TN90pct aspects relative to EHF and TX90pct are also observed. While qualitative information on event trends is similar across the indices, quantitative values vary. This result highlights the importance of employing the most appropriate index when assessing the impact of sustained extreme temperature events.”

Citation: Perkins, S. E., L. V. Alexander, and J. R. Nairn (2012), Increasing frequency, intensity and duration of observed global heatwaves and warm spells, Geophys. Res. Lett., 39, L20714, doi:10.1029/2012GL053361.


Fossil fuel facilities are predominant methane sources in winter over western Siberia

Contributions of natural and anthropogenic sources to atmospheric methane variations over western Siberia estimated from its carbon and hydrogen isotopes – Umezawa et al. (2012)

Abstract: “Aircraft measurements of carbon and hydrogen isotopic ratios of atmospheric CH4 (δ13CH4 and δD-CH4), with the respective precisions of 0.08‰ and 2.2‰, as well as CH4 concentration were made at 1 and 2 km altitudes over western Siberia during 2006–2009. δ13CH4 and δD-CH4 were almost always lower at lower altitudes, while the CH4 concentration was higher, implying strong sources on the ground with low isotopic values. δ13CH4 showed a clear seasonal minimum in the late summer, while seasonality of CH4 and δD-CH4 was ambiguous due to the local disturbances. By inspecting the relationships between the CH4 concentration and isotopes, we found that isotopic source signatures in the winter (December–April) are −41.2 ± 1.8 and −187 ± 18‰ for δ13CH4 and δD-CH4, respectively, and the corresponding values in the summer (June–October) are −65.0 ± 2.5 and −282 ± 25‰. These values indicate predominant CH4 emissions from fossil fuel facilities in the winter and wetlands in the summer. It was also found that the shorter-term CH4 variations are more influenced by fossil CH4 than that from wetlands. The finding presumably reflects the fact that the former is released from limited areas such as leakage from fossil fuel facilities, while the latter is released from a vast expanse of wetland. By employing a CH4 emission data set used in an atmospheric chemistry transport model, we calculated seasonal isotopic changes of CH4 sources in western Siberia and compared them to the estimates obtained in this study. The results indicated that the seasonal change in the CH4 emission data set is reasonable, at least in terms of a ratio of fossil to biogenic emissions.”

Citation: Umezawa, T., T. Machida, S. Aoki, and T. Nakazawa (2012), Contributions of natural and anthropogenic sources to atmospheric methane variations over western Siberia estimated from its carbon and hydrogen isotopes, Global Biogeochem. Cycles, 26, GB4009, doi:10.1029/2011GB004232.


Clouds could help deglaciating a Snowball Earth

Clouds and Snowball Earth deglaciation – Abbot et al. (2012) [FULL TEXT]

Abstract: “Neoproterozoic, and possibly Paleoproterozoic, glaciations represent the most extreme climate events in post-Hadean Earth, and may link closely with the evolution of the atmosphere and life. According to the Snowball Earth hypothesis, the entire ocean was covered with ice during these events for a few million years, during which time volcanic CO2 increased enough to cause deglaciation. Geochemical proxy data and model calculations suggest that the maximum CO2 was 0.01–0.1 by volume, but early climate modeling suggested that deglaciation was not possible at CO2 = 0.2. We use results from six different general circulation models (GCMs) to show that clouds could warm a Snowball enough to reduce the CO2 required for deglaciation by a factor of 10–100. Although more work is required to rigorously validate cloud schemes in Snowball-like conditions, our results suggest that Snowball deglaciation is consistent with observations.”

Citation: Abbot, D. S., A. Voigt, M. Branson, R. T. Pierrehumbert, D. Pollard, G. Le Hir, and D. D. B. Koll (2012), Clouds and Snowball Earth deglaciation, Geophys. Res. Lett., 39, L20711, doi:10.1029/2012GL052861.


Abrupt shutdown of Atlantic Meridional Overturning Circulation due to global warming seems unlikely

Stability of the Atlantic meridional overturning circulation: A model intercomparison – Weaver et al. (2012)

Abstract: “The evolution of the Atlantic Meridional Overturning Circulation (MOC) in 30 models of varying complexity is examined under four distinct Representative Concentration Pathways. The models include 25 Atmosphere-Ocean General Circulation Models (AOGCMs) or Earth System Models (ESMs) that submitted simulations in support of the 5th phase of the Coupled Model Intercomparison Project (CMIP5) and 5 Earth System Models of Intermediate Complexity (EMICs). While none of the models incorporated the additional effects of ice sheet melting, they all projected very similar behaviour during the 21st century. Over this period the strength of MOC reduced by a best estimate of 22% (18%–25%; 5%–95% confidence limits) for RCP2.6, 26% (23%–30%) for RCP4.5, 29% (23%–35%) for RCP6.0 and 40% (36%–44%) for RCP8.5. Two of the models eventually realized a slow shutdown of the MOC under RCP8.5, although no model exhibited an abrupt change of the MOC. Through analysis of the freshwater flux across 30°–32°S into the Atlantic, it was found that 40% of the CMIP5 models were in a bistable regime of the MOC for the duration of their RCP integrations. The results support previous assessments that it is very unlikely that the MOC will undergo an abrupt change to an off state as a consequence of global warming.”

Citation: Weaver, A. J., et al. (2012), Stability of the Atlantic meridional overturning circulation: A model intercomparison, Geophys. Res. Lett., 39, L20709, doi:10.1029/2012GL053763.


A review on adapting agriculture to climate change

Adapting agriculture to climate change: a review – Anwar et al. (2012)

Abstract: “The agricultural sector is highly vulnerable to future climate changes and climate variability, including increases in the incidence of extreme climate events. Changes in temperature and precipitation will result in changes in land and water regimes that will subsequently affect agricultural productivity. Given the gradual change of climate in the past, historically, farmers have adapted in an autonomous manner. However, with large and discrete climate change anticipated by the end of this century, planned and transformational changes will be needed. In light of these, the focus of this review is on farm-level and farmers responses to the challenges of climate change both spatially and over time. In this review of adapting agriculture to climate change, the nature, extent, and causes of climate change are analyzed and assessed. These provide the context for adapting agriculture to climate change. The review identifies the binding constraints to adaptation at the farm level. Four major priority areas are identified to relax these constraints, where new initiatives would be required, i.e., information generation and dissemination to enhance farm-level awareness, research and development (R&D) in agricultural technology, policy formulation that facilitates appropriate adaptation at the farm level, and strengthening partnerships among the relevant stakeholders. Forging partnerships among R&D providers, policy makers, extension agencies, and farmers would be at the heart of transformational adaptation to climate change at the farm level. In effecting this transformational change, sustained efforts would be needed for the attendant requirements of climate and weather forecasting and innovation, farmer’s training, and further research to improve the quality of information, invention, and application in agriculture. The investment required for these would be highly significant. The review suggests a sequenced approach through grouping research initiatives into short-term, medium-term, and long-term initiatives, with each initiative in one stage contributing to initiatives in a subsequent stage. The learning by doing inherent in such a process-oriented approach is a requirement owing to the many uncertainties associated with climate change.”

Citation: Muhuddin Rajin Anwar, De Li Liu, Ian Macadam and Georgina Kelly, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0780-1.


Ocean warming of the last century cannot be explained by natural variability

Evidence for external forcing on 20th-century climate from combined ocean-atmosphere warming patterns – Sedláček & Knutti (2012)

Abstract: “Of the additional energy absorbed by the Earth over the past decades, by far the largest fraction is taken up by the oceans. Yet most attribution studies focus on the surface warming, and only few have used patterns of ocean warming to attribute changes to external forcing or internal variability. Here we use the combined observed evidence from warming of the atmosphere and ocean with the latest climate model simulations to demonstrate that both the depth profiles and spatial warming patterns near the surface are very heterogeneous when resulting from internal unforced variability. In the 20th-century simulations on the other hand, the observed spatial pattern is smooth, and the warming decreases almost gradually with depth in the ocean, consistent with observations and a penetration of the surface warming to intermediate depth by diffusion and advection. We argue that such physically motivated arguments combining different lines of evidence and types of observations offer insight that is complementary to optimal fingerprint attribution methods. We conclude that the simultaneous global warming of the atmosphere and mixed layer alone is uninformative for attribution, but the magnitude of ocean heat uptake, the homogeneity of the spatial pattern as well as the distribution of warming below the mixed layer strongly argue for the 20th-century warming being largely externally forced.”

Citation: Sedláček, J. and R. Knutti (2012), Evidence for external forcing on 20th-century climate from combined ocean-atmosphere warming patterns, Geophys. Res. Lett., 39, L20708, doi:10.1029/2012GL053262.


Increasing seabed temperatures make gas hydrate unstable in shallow Norwegian-Svalbard margin regions

Ocean temperature variability for the past 60 years on the Norwegian-Svalbard margin influences gas hydrate stability on human time scales – Ferré et al. (2012)

Abstract: “The potential impact of future climate change on methane release from oceanic gas hydrates is the subject of much debate. We analyzed World Ocean Database quality controlled data on the Norwegian-Svalbard continental margin from the past 60 years to evaluate the potential effect of ocean temperature variations on continental margin gas hydrate reservoirs. Bottom water temperatures in the Norwegian-Svalbard margin were subject to significant cooling until 1980 (by ∼2°C offshore NW-Svalbard and in the Barents Sea) followed by a general bottom water temperature increase until 2010 (∼0.3°C in deep-water areas offshore NW-Svalbard and mid-Norwegian margin and ∼2°C in the shallow areas of the Barents Sea and Prins Karls Forland). Bottom water warming in the shallow outer shelf areas triggered the Gas Hydrate Stability Zone (GHSZ) retreat toward upper continental slope areas, potentially increasing methane release due to gas hydrate dissociation. GHSZ responses to temperature changes on human time scales occur exclusively in shallow water and only if near-surface gas hydrates exist. The responses are associated with a short time lag of less than 1 year. Temperatures in the bottom water column seem to be partly regulated by the North Atlantic Oscillation (NAO), with positive NAO associated with warm phases. However, cooling events in the surface water offshore NW-Svalbard might be associated with El Niño events of 1976–1977, 1986–1987 and 1997–1998 in the Pacific. Such ocean cooling, if long enough, may delay ocean temperature driven gas hydrate dissociation and potential releases of methane to the ocean.”

Citation: Ferré, B., J. Mienert, and T. Feseker (2012), Ocean temperature variability for the past 60 years on the Norwegian-Svalbard margin influences gas hydrate stability on human time scales, J. Geophys. Res., 117, C10017, doi:10.1029/2012JC008300.


Other studies from last week

Connecting Changing Ocean Circulation with Changing Climate – Winton et al. (2012)

Surface irradiances consistent with CERES-derived top-of-atmosphere shortwave and longwave irradiances – Kato et al. (2012)

The extreme melt across the Greenland ice sheet in 2012 – Nghiem et al. (2012)

What caused the cool summer over northern Central Asia, East Asia and central North America during 2009? – Ha et al. (2012) [FULL TEXT]

Carbon dioxide emission from temperate semiarid steppe during the non-growing season – Chen et al. (2012)

A 7000 year record of paleohurricane activity from a coastal wetland in Belize – McCloskey & Liu et al. (2012)

Global Warming Shifts The Monsoon Circulation, Drying South Asia – Annamalai et al. (2012)

Were Pleistocene hippopotamuses exposed to climate-driven body size changes? – Mazza & Bertini (2012)

Climate change has indirect effects on resource use and overlap among coexisting bird species with negative consequences for their reproductive success – Auer & Martin (2012)

Sea ice inertial oscillations in the Arctic Basin – Gimbert et al. (2012) [FULL TEXT]

Can aerosol loading explain the solar dimming over the Tibetan Plateau? – Yang et al. (2012)

Identifying the causes of the poor decadal climate prediction skill over the North Pacific – Guemas et al. (2012)

Examining vegetation feedbacks on global warming in the Community Earth System Model – Pu & Dickinson (2012)

Trends in seasonal precipitation and temperature in Slovenia during 1951–2007 – de Luis et al. (2012)

Coupled CO2-climate response during the Early Eocene Climatic Optimum – Hyland & Sheldon (2012)

Atmospheric impacts on climatic variability of surface incident solar radiation – Wang et al. (2012) [FULL TEXT]

Northern peatland carbon stocks and dynamics: a review – Yu (2012) [FULL TEXT]

How may low-cloud radiative properties simulated in the current climate influence low-cloud feedbacks under global warming? – Brient & Bony (2012)

A continuous simulation of global ice volume over the past 1 million years with 3-D ice-sheet models – de Boer et al. (2012)


CLASSIC OF THE WEEK: Humphreys (1909)

Vertical Temperature-Gradients of the Atmosphere, Especially in the Region of Upper Inversion – Humphreys (1909) [FULL TEXT]

Abstract: No abstract.

Citation: Humphreys, W. J., Astrophysical Journal, vol. 29, p.14, DOI: 10.1086/141615.


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

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New research from last week 42/2012

Posted by Ari Jokimäki on October 22, 2012

This week’s papers look into rice growth, ice sheet temperature response, invasive species, Greenland temperatures, global warming trends, carbon dioxide emissions, sea level, solar forcing, ozone depletion, ski tourism, tropopause, and sea ice vs. winter climate.


Link between Arctic sea ice reduction and cold winters in Europe

Trends Arctic sea ice reduction and European cold winters in CMIP5 climate change experiments – Yang & Christensen (2012)

Abstract: “European winter climate and its possible relationship with the Arctic sea ice reduction in the recent past and future as simulated by the models of the Climate Model Intercomparison Project phase 5 (CMIP5) is investigated, with focus on the cold winters. While Europe will warm overall in the future, we find that episodes of cold months will continue to occur and there remains substantial probability for the occurrence of cold winters in Europe linked with sea ice reduction in the Barents and Kara Sea sector. A pattern of cold-European warm-Arctic anomaly is typical for the cold events in the future, which is associated with the negative phase of the Arctic Oscillation. These patterns, however, differ from the corresponding patterns in the historical period, and underline the connection between European cold winter events and Arctic sea ice reduction.”

Citation: Yang, S. and J. H. Christensen (2012), Arctic sea ice reduction and European cold winters in CMIP5 climate change experiments, Geophys. Res. Lett., 39, L20707, doi:10.1029/2012GL053338.


Tropopause is getting thicker

Trends in the global tropopause thickness revealed by radiosondes – Feng et al. (2012)

Abstract: “The first global trends in the thickness of the tropopause layer (TL) are analyzed based on radiosonde data in the Integrated Global Radiosonde Archive (IGRA) for the period of 1965–2004. It reveals that TL has been thickening for the entire globe with positive trends of 0.16 ± 0.12 km/decade during this period. Statistically significant thickening is observed in the tropics, North Hemisphere (NH) extratropics, and NH poles. Accompanied by overall cooling of −0.58 ± 0.40 K/decade in TL’s top, remarkable rising trends of 0.35 ± 0.29 km/decade are observed in the correspoding height. However, the anti-correlation of the trends in the tropopause temperature and the corresponding height is not observed in its lower boundary, namely the first lapse rate tropopause (LRT), for all the latitude bands as suggested by the previous studies. The results imply that the temperature of the TL is primarily couple with the height of its upper boundary as the thickness of the TL is more correlated with the temperature of the lower stratosphere than with the tempeature of the upper troposphere. Long-term changes in TL may in turn carry more information how tropopause change in response to climate change than in the sharp “tropopause surface” only.”

Citation: Feng, S., Y. Fu, and Q. Xiao (2012), Trends in the global tropopause thickness revealed by radiosondes, Geophys. Res. Lett., 39, L20706, doi:10.1029/2012GL053460.


How climate change affects Australian ski tourism flow to New Zealand

Climate change in a regional context: relative vulnerability in the Australasian skier market – Hopkins et al. (2012)

Abstract: “The concept of relative vulnerability allows for comparisons between analogous units in a regional context. It is utilised within tourism studies to consider how climate change might affect demand and perceived attractiveness of destinations relative to their competitors. This paper examines Australian tourists travelling to New Zealand’s ski fields, responding to the intergovernmental panel on climate change (IPCC) assertion that, “tourist flows from Australia to New Zealand might grow as a result of the relatively poorer snow conditions in Australia” (Hennessy et al. 2007: p 523). This travel flow is not a new phenomenon; however, it is forecast to increase as climate change impacts upon Australia’s natural and man-made snowmaking capacity with implications for the viability of the ski industries in both Australia and New Zealand. The Queenstown Lakes Region (South Island, New Zealand) serves as the field area for this study. The empirical research utilises a qualitative methodology for which in-depth, semi-structured interviews were conducted with New Zealand ski industry representatives and Australian tourists during the southern hemisphere winter season of 2011. Findings suggest that the social context of vulnerability creates difficulty in forecasting the outcomes and behaviours associated with relative vulnerability. While tourism representatives’ focus on snow reliability and availability to conceptualise relative vulnerability, Australian tourists are influenced by a broader range of factors including their own travel experience. This paper demonstrates a clear need to move beyond a focus on snow reliability to consider the broad range of factors that contribute to regional variations in vulnerability. In doing so, it confirms the critical importance of situating relative vulnerability within a social context.”

Citation: Debbie Hopkins, James E. S. Higham and Susanne Becken, Regional Environmental Change, 2012, DOI: 10.1007/s10113-012-0352-z.


Stratospheric ozone depletion warms Antarctic surface and ocean

Antarctic climate response to stratospheric ozone depletion in a fine resolution ocean climate model – Bitz & Polvani (2012) [FULL TEXT]

Abstract: “We investigate the impact of stratospheric ozone depletion on Antarctic climate, paying particular attention to the question of whether eddy parameterizations in the ocean fundamentally alter the results. This is accomplished by contrasting two versions of the Community Climate System Model (version 3.5), one at 0.1° ocean and sea ice resolution and the other at 1° with parameterized ocean eddies. At both resolutions, pairs of integrations are performed: one with high (1960) and one with low (2000) ozone levels. We find that the effect of ozone depletion is to warm the surface and the ocean to a depth of 1000 m and to significantly reduce the sea ice extent. While the ocean warming is somewhat weaker when the eddies are resolved, the total loss of sea ice area is roughly the same in the fine and coarse resolution cases.”

Citation: Bitz, C. M. and L. M. Polvani (2012), Antarctic climate response to stratospheric ozone depletion in a fine resolution ocean climate model, Geophys. Res. Lett., 39, L20705, doi:10.1029/2012GL053393.


Solar forcing of climate during last millennium in northern Sweden

Solar forcing of climate during the last millennium recorded in lake sediments from northern Sweden – Kokfelt & Muscheler (2012)

Abstract: “We report on a sediment record from a small lake within the subarctic wetland complex Stordalen in northernmost Sweden covering the last 1000 years. Variations in the content of minerogenic material are found to follow reconstructed variations in the activity of the Sun between the 13th and 18th centuries. Periods of low solar activity are associated with minima in minerogenic material and vice versa. A comparison between the sunspot cycle and a long instrumental series of summer precipitation further reveals a link between the 11 yr solar cycle and summer precipitation variability since around 1960. Solar minima are in this period associated with minima in summer precipitation, whereas the amount of summer precipitation increases during periods with higher solar activity. Our results suggest that the climate responds to both the 11 yr solar cycle and to long-term changes in solar activity and in particular solar minima, causing dry conditions with resulting decreased runoff.”

Citation: U Kokfelt, R Muscheler, The Holocene October 18, 2012 0959683612460781, doi: 10.1177/0959683612460781.


New study suggests 0.25 m increase to upper bound of sea level rise by 2100

Toward a physically plausible upper bound of sea-level rise projections – Sriver et al. (2012)

Abstract: “Anthropogenic sea-level rise (SLR) causes considerable risks. Designing a sound SLR risk-management strategy requires careful consideration of decision-relevant uncertainties such as the reasonable upper bound of future SLR. The recent Intergovernmental Panel on Climate Change’s (IPCC) Fourth Assessment reported a likely upper SLR bound in the year 2100 near 0.6 m (meter). More recent studies considering semi-empirical modeling approaches and kinematic constraints on glacial melting suggest a reasonable 2100 SLR upper bound of approximately 2 m. These recent studies have broken important new ground, but they largely neglect uncertainties surrounding thermal expansion (thermosteric SLR) and/or observational constraints on ocean heat uptake. Here we quantify the effects of key parametric uncertainties and observational constraints on thermosteric SLR projections using an Earth system model with a dynamic three-dimensional ocean, which provides a mechanistic representation of deep ocean processes and heat uptake. Considering these effects nearly doubles the contribution of thermosteric SLR compared to previous estimates and increases the reasonable upper bound of 2100 SLR projections by 0.25 m. As an illustrative example of the effect of overconfidence, we show how neglecting thermosteric uncertainty in projections of the SLR upper bound can considerably bias risk analysis and hence the design of adaptation strategies. For conditions close to the Port of Los Angeles, the 0.25 m increase in the reasonable upper bound can result in a flooding-risk increase by roughly three orders of magnitude. Results provide evidence that relatively minor underestimation of the upper bound of projected SLR can lead to major downward biases of future flooding risks.”

Citation: Ryan L. Sriver, Nathan M. Urban, Roman Olson and Klaus Keller, Climatic Change, 2012, DOI: 10.1007/s10584-012-0610-6.


Fraction of natural area can be used as a proxy for urban carbon dioxide emissions

Fraction of natural area as main predictor of net CO2 emissions from cities – Nordbo et al. (2012)

Abstract: “Cities account for most anthropogenic greenhouse-gas emissions, CO2 being most important. We evaluate the net urban contribution to CO2 emissions by performing a meta-analysis of all available 14 annual CO2 budget studies. The studies are based on direct flux measurements using the eddy-covariance technique which excludes all strong point sources. We show that the fraction of natural area is the strongest predictor of urban CO2 budgets, and this fraction can be used as a robust proxy for net urban CO2 emissions. Up-scaling, based on that proxy and satellite mapping of the fraction of natural area, identifies urban hotspots of CO2 emissions; and extraction of 56 individual cities corroborates their inventory-based estimates. Furthermore, cities are estimated as carbon-neutral when the natural fraction is about 80%. This fresh view on the importance of cities in climate change treats cities as urban ecosystems: incorporating natural areas like vegetation.”

Citation: Nordbo, A., L. Jarvi, S. Haapanala, C. R. Wood, and T. Vesala (2012), Fraction of natural area as main predictor of net CO2 emissions from cities, Geophys. Res. Lett., doi:10.1029/2012GL053087.


Anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years

Deducing Multi-decadal Anthropogenic Global Warming Trends Using Multiple Regression Analysis – Zhou & Tung (2012)

Abstract: “In order to unmask the anthropogenic global warming trend imbedded in the climate data, multiple linear regression analysis is often employed to filter out short-term fluctuations caused by El Nino-Southern Oscillation (ENSO), volcano aerosols and solar forcing. These fluctuations are unimportant as far as their impact on the deduced multidecadal anthropogenic trends is concerned: ENSO and volcano aerosols have very little multi-decadal trend. Solar variations do have a secular trend, but it is very small and uncertain. What is important, but is left out of all multiple regression analysis of global warming so far, is a long-perioded oscillation called the Atlantic Multi-decadal Oscillation (AMO). When the AMO Index is included as a regressor (i.e. explanatory variable), the deduced multi-decadal anthropogenic global warming trend is so impacted that previously deduced anthropogenic warming rates need to be substantially revised. The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.”

Citation: Jiansong Zhou and Ka-Kit Tung, Journal of the Atmospheric Sciences 2012.


Current warming in northern Greenland is unprecedented in the past 2400 years

Twentieth-century warming revives the world’s northernmost lake – Perren et al. (2012)

Abstract: “Although recent ecological changes are widespread in Arctic lakes, it remains unclear whether they are more strongly associated with climate warming or the deposition of reactive nitrogen (Nr) from anthropogenic sources. We developed a 3500-yr paleolimnological record from the world’s northernmost lake to explore this question. Microfossils indicate that siliceous diatoms and chrysophytes were abundant initially, but disappeared 2400 yr ago in concert with Neoglacial cooling. Microfossils reappear in 20th-century sediments and reach unprecedented concentrations in sediments deposited after ca. A.D. 1980, tracking increasing summer temperatures in the absence of evidence for atmospheric nutrient subsidies. These results indicate that current warming in northern Greenland is unprecedented in the context of the past 2400 yr, and that climate change alone is responsible for the marked biological changes observed.”

Citation: Bianca B. Perren, Alexander P. Wolfe, Colin A. Cooke, Kurt H. Kjær, David Mazzucchi and Eric J. Steig, Geology, v. 40 no. 11 p. 1003-1006, doi: 10.1130/G33621.1.


Climate change effects on invasive species versus native species

Poised to prosper? A cross-system comparison of climate change effects on native and non-native species performance – Sorte et al. (2012) [FULL TEXT]

Abstract: “Climate change and biological invasions are primary threats to global biodiversity that may interact in the future. To date, the hypothesis that climate change will favour non-native species has been examined exclusively through local comparisons of single or few species. Here, we take a meta-analytical approach to broadly evaluate whether non-native species are poised to respond more positively than native species to future climatic conditions. We compiled a database of studies in aquatic and terrestrial ecosystems that reported performance measures of non-native (157 species) and co-occurring native species (204 species) under different temperature, CO2 and precipitation conditions. Our analyses revealed that in terrestrial (primarily plant) systems, native and non-native species responded similarly to environmental changes. By contrast, in aquatic (primarily animal) systems, increases in temperature and CO2 largely inhibited native species. There was a general trend towards stronger responses among non-native species, including enhanced positive responses to more favourable conditions and stronger negative responses to less favourable conditions. As climate change proceeds, aquatic systems may be particularly vulnerable to invasion. Across systems, there could be a higher risk of invasion at sites becoming more climatically hospitable, whereas sites shifting towards harsher conditions may become more resistant to invasions.”

Citation: Cascade J. B. Sorte, Ines Ibáñez, Dana M. Blumenthal, Nicole A. Molinari, Luke P. Miller, Edwin D. Grosholz, Jeffrey M. Diez, Carla M. D’Antonio, Julian D. Olden, Sierra J. Jones, Jeffrey S. Dukes, Ecology Letters, DOI: 10.1111/ele.12017.


Lagged ice-margin temperature response of Greenland ice sheet implies that significant retreat may be yet to come

Maximum late Holocene extent of the western Greenland Ice Sheet during the late 20th century – Kelley et al. (2012)

Abstract: “The pattern of Greenland Ice Sheet margin change during the 20th century is variable. Large-scale retreat of marine-outlet glaciers contrasts with the often-negligible retreat observed along land-terminating margins of the ice sheet. We reconstruct a chronology of ice-margin change for two land-terminating ice margins in western Greenland using radiocarbon and 10Be exposure dating. Our results indicate that two land-terminating lobes attained their maximum late Holocene position in the late 20th century. This contrasts with the nearby marine-terminating Jakobshavn Isbræ, which achieved a maximum late Holocene position during the Little Ice Age, and has since retreated ca 40 km. In addition, we survey ice-margin change across western Greenland, utilizing satellite imagery. We find that many land-terminating sectors of the ice sheet, in addition to our study area, may have attained their maximum late Holocene extent during the 20th century. This suggests a lagged ice-margin response to prior cooling, such as the Little Ice Age, which would imply significant retreat of land-terminating sections of the Greenland Ice Sheet in response to 20th and 21st century warming may be yet to come.”

Citation: Samuel E. Kelley, Jason P. Briner, Nicolás E. Young, Gregory S. Babonis, Bea Csatho, Quaternary Science Reviews, Volume 56, 21 November 2012, Pages 89–98, http://dx.doi.org/10.1016/j.quascirev.2012.09.016.


Major temperature-induced change of the rice growth duration is underway in China

Climate warming over the past three decades has shortened rice growth duration in China and cultivar shifts have further accelerated the process for late rice – Zhang et al. (2012)

Abstract: “An extensive dataset on rice phenology in China, including 202 series broadly covering the past three decades (1980s–2000s), was compiled. From these data, we estimated the responses of growth duration length to temperature using a regression model based on the data with and without de-trending. Regression coefficients derived from the de-trended data reflect only the temperature effect, whereas those derived from data without de-trending represent a combined effect of temperature and confounding cultivar shifts. Results indicate that the regression coefficients calculated from the data with and without de-trending show an average shortening of the growth duration of 4.1 to 4.4 days for each additional increase in temperature over the full growth cycle. Using the de-trended data, 95.0% of the data series exhibited a negative correlation between the growth duration length and temperature; this correlation was significant in 61.9% of all of the data series. We then compared the difference between the two regression coefficients calculated from data with and without de-trending and found a significantly greater temperature sensitivity using the data without de-trending (-2.9 days °C-1) than that derived from the de-trended data (-2.0 days °C-1) in the period of emergence to heading for the late rice, producing a negative difference in temperature sensitivity (-0.9 days °C-1). This implies that short-duration cultivars were planted with increase in temperature and exacerbated the undesired phenological change. In contrast, positive differences were detected for the single (0.6 days °C-1) and early rice (0.5 days °C-1) over the full growth cycle, which might indicate long-duration cultivars were favoured with climate warming, but these differences were insignificant. In summary, our results suggest that a major, temperature-induced change of the rice growth duration is underway in China and that using a short-duration cultivar has been accelerating the process for late rice.”

Citation: Tianyi Zhang, Yao Huang, Xiaoguang Yang, Global Change Biology, DOI: 10.1111/gcb.12057.


Other studies from last week

The Reversibility of Sea Level Rise – Bouttes et al. (2012)

The tropical precipitation response to orbital precession – Merlis et al. (2012)

Regional changes in wind energy potential over Europe using regional climate model ensemble projections – Hueging et al. (2012)

Observed Tropospheric Temperature Response to 11-Year Solar Cycle, And What It Reveals About Mechanisms – Zhou & Tung (2012)

How well do climate models simulate cloud vertical structure? A comparison between CALIPSO-GOCCP satellite observations and CMIP5 models – Cesana & Chepfer (2012)

A fifty year record of winter glacier melt events in southern Chile, 38°–42°S – Brock et al. (2012) [FULL TEXT]

Is a Transition to Semi-Permanent Drought Conditions Imminent in the U.S. Great Plains? – Hoerling et al. (2012)

Seasonal changes in solar radiation and relative humidity in Europe in response to global warming – Ruosteenoja & Räisanen (2012)

On the linear additivity of climate forcing-response relationships at global and continental scales – Shiogama et al. (2012)

Alpine snow cover in a changing climate: a regional climate model perspective – Steger et al. (2012)

The response of methane and nitrous oxide fluxes to forest change in Europe – Gundersen et al. (2012) [FULL TEXT]

Approaches for inclusion of forest carbon cycle in life cycle assessment – a review – Helin et al. (2012)

Radiative budget and cloud radiative effect over the Atlantic from ship-based observations – Kalisch & Macke (2012) [FULL TEXT]

Global runoff anomalies over 1993–2009 estimated from coupled Land–Ocean–Atmosphere water budgets and its relation with climate variability – Munier et al. (2012) [FULL TEXT]

High-resolution interpolar difference of atmospheric methane around the Last Glacial Maximum – Baumgartner et al. (2012) [FULL TEXT]

Uncertainty in the ENSO amplitude change from the past to the future – Watanabe et al. (2012)

How tillite weathering during the snowball Earth aftermath induced cap carbonate deposition – Fabre & Berger (2012)

The impact of the El Niño-Southern Oscillation on maximum temperature extremes – Arblaster & Alexander (2012)

Mitigation of 21st century Antarctic sea ice loss by stratospheric ozone recovery – Smith et al. (2012)

Mild Little Ice Age and unprecedented recent warmth in an 1800 year lake sediment record from Svalbard – D’Andrea et al. (2012)

Late glacial fluctuations of Quelccaya Ice Cap, southeastern Peru – Kelly et al. (2012)

Impacts of climate change on primary production and carbon sequestration of boreal Norway spruce forests: Finland as a model – Ge et al. (2012)

A 7000 year record of paleohurricane activity from a coastal wetland in Belize – McCloskey & Liu (2012)


CLASSIC OF THE WEEK: Setchell (1915)

The Law of Temperature Connected with the Distribution of the Marine Algae – Setchell (1915) [FULL TEXT]

Abstract: No abstract. First paragraph: “What I have to bring before you is simply a preliminary consideration of the general subject of the geographical dis- tribution of the marine algae together with some inquiry into the conditions immediately affecting such distribution and as possibly effecting a segregation into the larger units. In accordance with such an intention, I have started a tabula- tion of all the marine species and varieties, which is far from being completed as yet, but which has, however, reached a stage at which certain general statements may be made as to probable results.”

Citation: William Albert Setchell, Annals of the Missouri Botanical Garden, Vol. 2, No. 1/2, Anniversary Proceedings (Feb. – Apr., 1915) (pp. 287-305).


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 1 Comment »

Papers on Arctic amplification

Posted by Ari Jokimäki on October 17, 2012

This is a list of papers on Arctic amplification. Also general papers on polar amplification and Antarctic amplification are included (most commonly known term for the phenomenon is Arctic amplification which is why it is used in the title). The list is not complete, and will most likely be updated in future in order to make it more thorough and more representative.

Note that there is a separate list of papers on ice-albedo feedback, many of which are relevant to this subject also.

Processes and impacts of Arctic amplification: A research synthesis – Serreze & Barry (2011) “The past decade has seen substantial advances in understanding Arctic amplification — that trends and variability in surface air temperature tend to be larger in the Arctic region than for the Northern Hemisphere or globe as a whole. We provide a synthesis of research on Arctic amplification, starting with a historical context and then addressing recent insights into processes and key impacts, based on analysis of the instrumental record, modeling studies, and paleoclimate reconstructions. Arctic amplification is now recognized as an inherent characteristic of the global climate system, with multiple intertwined causes operating on a spectrum of spatial and temporal scales. These include, but are not limited to, changes in sea ice extent that impact heat fluxes between the ocean and the atmosphere, atmospheric and oceanic heat transports, cloud cover and water vapor that alter the longwave radiation flux to the surface, soot on snow and heightened black carbon aerosol concentrations. Strong warming over the Arctic Ocean during the past decade in autumn and winter, clearly associated with reduced sea ice extent, is but the most recent manifestation of the phenomenon. Indeed, periods of Arctic amplification are evident from analysis of both warm and cool periods over at least the past three million years. Arctic amplification being observed today is expected to become stronger in coming decades, invoking changes in atmospheric circulation, vegetation and the carbon cycle, with impacts both within and beyond the Arctic.” Mark C. Serreze, Roger G. Barry, Global and Planetary Change, Volume 77, Issues 1–2, May 2011, Pages 85–96, http://dx.doi.org/10.1016/j.gloplacha.2011.03.004. [FULL TEXT]

The impact of the Madden-Julian Oscillation trend on the Arctic amplification of surface air temperature during the 1979–2008 boreal winter – Yoo et al. (2011) “One of the most prominent and important features of climate change is that surface air temperature (SAT) change is greatest at high latitudes. The cause for this Arctic amplification of SAT is uncertain. Using ERA-Interim reanalysis data, we show that Arctic amplification during the past 30 years (1979 to 2008) is linked to the Madden-Julian Oscillation (MJO), the primary mode of intraseasonal variability in the tropics. Specifically, it is shown that interdecadal changes in the frequency of occurrence of individual MJO phases have had considerable influence on the Arctic warming during the boreal winter. During that time period, MJO phases 4–6 exhibited a large increase and phases 1–2 a moderate decrease in their frequency of occurrence. Time lagged composites of the SAT show that MJO phases 4–6, which correspond to enhanced localized tropical heating, are followed 1–2 weeks later by Arctic warming. Similarly, MJO phases 1–2, which are associated with more zonally uniform tropical heating, are followed by Arctic cooling. These relationships between the Arctic SAT and the spatial structure of the tropical heating are consistent with the poleward propagation mechanism of Lee et al. (2011a, 2011b). By incorporating both the trend in MJO phase and the intraseasonal SAT anomaly associated with the MJO, it was found that the MJO-induced SAT trend accounts for 10–20% of the observed Arctic amplification over the Arctic Ocean.” Yoo, C., S. Feldstein, and S. Lee (2011), The impact of the Madden-Julian Oscillation trend on the Arctic amplification of surface air temperature during the 1979–2008 boreal winter, Geophys. Res. Lett., 38, L24804, doi:10.1029/2011GL049881. [FULL TEXT]

Arctic amplification: can the past constrain the future? – Miller et al. (2010) “Arctic amplification, the observation that surface air temperature changes in the Arctic exceed those of the Northern Hemisphere as a whole, is a pervasive feature of climate models, and has recently emerged in observational data relative to the warming trend of the past century. The magnitude of Arctic amplification is an important, but poorly constrained variable necessary to estimate global average temperature change over the next century. Here we evaluate the mechanisms responsible for Arctic amplification on Quaternary timescales, and review evidence from four intervals in the past 3 Ma for which sufficient paleoclimate data and model simulations are available to estimate the magnitude of Arctic amplification under climate states both warmer and colder than present. Despite differences in forcings and feedbacks for these reconstructions compared to today, the Arctic temperature change consistently exceeds the Northern Hemisphere average by a factor of 3–4, suggesting that Arctic warming will continue to greatly exceed the global average over the coming century, with concomitant reductions in terrestrial ice masses and, consequently, an increasing rate of sea level rise.” Gifford H. Miller, Richard B. Alley, Julie Brigham-Grette, Joan J. Fitzpatrick, Leonid Polyak, Mark C. Serreze, James W.C. White, Quaternary Science Reviews, Volume 29, Issues 15–16, July 2010, Pages 1779–1790, http://dx.doi.org/10.1016/j.quascirev.2010.02.008. [FULL TEXT]

The central role of diminishing sea ice in recent Arctic temperature amplification – Screen & Simmonds (2010) “The rise in Arctic near-surface air temperatures has been almost twice as large as the global average in recent decades — a feature known as ‘Arctic amplification’. Increased concentrations of atmospheric greenhouse gases have driven Arctic and global average warming; however, the underlying causes of Arctic amplification remain uncertain. The roles of reductions in snow and sea ice cover and changes in atmospheric and oceanic circulation, cloud cover and water vapour are still matters of debate. A better understanding of the processes responsible for the recent amplified warming is essential for assessing the likelihood, and impacts, of future rapid Arctic warming and sea ice loss. Here we show that the Arctic warming is strongest at the surface during most of the year and is primarily consistent with reductions in sea ice cover. Changes in cloud cover, in contrast, have not contributed strongly to recent warming. Increases in atmospheric water vapour content, partly in response to reduced sea ice cover, may have enhanced warming in the lower part of the atmosphere during summer and early autumn. We conclude that diminishing sea ice has had a leading role in recent Arctic temperature amplification. The findings reinforce suggestions that strong positive ice–temperature feedbacks have emerged in the Arctic, increasing the chances of further rapid warming and sea ice loss, and will probably affect polar ecosystems, ice-sheet mass balance and human activities in the Arctic.” James A. Screen & Ian Simmonds, Nature, 464, 1334–1337, 29 April 2010, DOI: doi:10.1038/nature09051. [FULL TEXT]

Contribution of sea ice loss to Arctic amplification – Kumar et al. (2010) “Atmospheric climate models are subjected to the observed sea ice conditions during 2007 to estimate the regionality, seasonality, and vertical pattern of temperature responses to recent Arctic sea ice loss. It is shown that anomalous sea ice conditions accounted for virtually all of the estimated Arctic amplification in surface-based warming over the Arctic Ocean, and furthermore they accounted for a large fraction of Arctic amplification occurring over the high-latitude land between 60°N and the Arctic Ocean. Sea ice loss did not appreciably contribute to observed 2007 land temperature warmth equatorward of 60°N. Likewise, the observed warming of the free atmosphere attributable to sea ice loss is confined to Arctic latitudes, and is vertically confined to the lowest 1000 m. The results further highlight a strong seasonality of the temperature response to the 2007 sea ice loss. A weak signal of Arctic amplification in surface based warming is found during boreal summer, whereas a dramatically stronger signal is shown to develop during early autumn that persisted through December even as sea ice coverage approached its climatological values in response to the polar night.” Kumar, A., J. Perlwitz, J. Eischeid, X. Quan, T. Xu, T. Zhang, M. Hoerling, B. Jha, and W. Wang (2010), Contribution of sea ice loss to Arctic amplification, Geophys. Res. Lett., 37, L21701, doi:10.1029/2010GL045022. [FULL TEXT]

Role of Polar Amplification in Long-Term Surface Air Temperature Variations and Modern Arctic Warming – Bekryaev et al. (2009) “This study uses an extensive dataset of monthly surface air temperature (SAT) records (including previously unutilized) from high-latitude (>60°N) meteorological land stations. Most records have been updated by very recent observations (up to December 2008). Using these data, a high-latitude warming rate of 1.36°C century−1 is documented for 1875–2008—the trend is almost 2 times stronger than the Northern Hemisphere trend (0.79°C century−1), with an accelerated warming rate in the most recent decade (1.35°C decade−1). Stronger warming in high-latitude regions is a manifestation of polar amplification (PA). Changes in SAT suggest two spatial scales of PA—hemispheric and local. A new stable statistical measure of PA linking high-latitude and hemispheric temperature anomalies via a regression relationship is proposed. For 1875–2008, this measure yields PA of 1.62. Local PA related to the ice–albedo feedback mechanisms is autumnal and coastal, extending several hundred kilometers inland. Heat budget estimates suggest that a recent reduction of arctic ice and anomalously high SATs cannot be explained by ice–albedo feedback mechanisms alone, and the role of large-scale mechanisms of PA of global warming should not be overlooked.” Bekryaev, Roman V., Igor V. Polyakov, Vladimir A. Alexeev, 2010: Role of Polar Amplification in Long-Term Surface Air Temperature Variations and Modern Arctic Warming. J. Climate, 23, 3888–3906. doi: http://dx.doi.org/10.1175/2010JCLI3297.1. [FULL TEXT]

The emergence of surface-based Arctic amplification – Serreze et al. (2009) “Rises in surface and lower troposphere air temperatures through the 21st century are projected to be especially pronounced over the Arctic Ocean during the cold season. This Arctic amplification is largely driven by loss of the sea ice cover, allowing for strong heat transfers from the ocean to the atmosphere. Consistent with observed reductions in sea ice extent, fields from both the NCEP/NCAR and JRA-25 reanalyses point to emergence of surface-based Arctic amplification in the last decade.” Serreze, M. C., Barrett, A. P., Stroeve, J. C., Kindig, D. N., and Holland, M. M.: The emergence of surface-based Arctic amplification, The Cryosphere, 3, 11-19, doi:10.5194/tc-3-11-2009, 2009. [FULL TEXT]

Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation – Chylek et al. (2009) “Understanding Arctic temperature variability is essential for assessing possible future melting of the Greenland ice sheet, Arctic sea ice and Arctic permafrost. Temperature trend reversals in 1940 and 1970 separate two Arctic warming periods (1910–1940 and 1970–2008) by a significant 1940–1970 cooling period. Analyzing temperature records of the Arctic meteorological stations we find that (a) the Arctic amplification (ratio of the Arctic to global temperature trends) is not a constant but varies in time on a multi-decadal time scale, (b) the Arctic warming from 1910–1940 proceeded at a significantly faster rate than the current 1970–2008 warming, and (c) the Arctic temperature changes are highly correlated with the Atlantic Multi-decadal Oscillation (AMO) suggesting the Atlantic Ocean thermohaline circulation is linked to the Arctic temperature variability on a multi-decadal time scale.” Chylek, P., C. K. Folland, G. Lesins, M. K. Dubey, and M. Wang (2009), Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation, Geophys. Res. Lett., 36, L14801, doi:10.1029/2009GL038777. [FULL TEXT]

The Arctic Amplification Debate – Serreze & Francis (2006) “Rises in surface air temperature (SAT) in response to increasing concentrations of greenhouse gases (GHGs) are expected to be amplified in northern high latitudes, with warming most pronounced over the Arctic Ocean owing to the loss of sea ice. Observations document recent warming, but an enhanced Arctic Ocean signal is not readily evident. This disparity, combined with varying model projections of SAT change, and large variability in observed SAT over the 20th century, may lead one to question the concept of Arctic amplification. Disparity is greatly reduced, however, if one compares observed trajectories to near-future simulations (2010–2029), rather than to the doubled-CO2 or late 21st century conditions that are typically cited. These near-future simulations document a preconditioning phase of Arctic amplification, characterized by the initial retreat and thinning of sea ice, with imprints of low-frequency variability. Observations show these same basic features, but with SATs over the Arctic Ocean still largely constrained by the insulating effects of the ice cover and thermal inertia of the upper ocean. Given the general consistency with model projections, we are likely near the threshold when absorption of solar radiation during summer limits ice growth the following autumn and winter, initiating a feedback leading to a substantial increase in Arctic Ocean SATs.” Mark C. Serreze and Jennifer A. Francis, Climatic Change, Volume 76, Numbers 3-4 (2006), 241-264, DOI: 10.1007/s10584-005-9017-y. [FULL TEXT]

Amplified Arctic climate change: What does surface albedo feedback have to do with it? – Winton (2006) “A group of twelve IPCC fourth assessment report (AR4) climate models have Arctic (60N–90N) warmings that are, on average, 1.9 times greater than their global warmings at the time of CO2 doubling in 1%/year CO2 increase experiments. Forcings and feedbacks that impact the warming response are estimated for both Arctic and global regions based on standard model diagnostics. Fitting a zero-dimensional energy balance model to each region, an expression is derived that gives the Arctic amplification as a function of these forcings and feedbacks. Contributing to Arctic amplification are the Arctic-global differences in surface albedo feedback (SAF), longwave feedback and the net top-of-atmosphere flux forcing (the sum of the surface flux and the atmospheric heat transport convergence). The doubled CO2 forcing and non-SAF shortwave feedback oppose Arctic amplification. SAF is shown to be a contributing, but not a dominating, factor in the simulated Arctic amplification and its intermodel variation.” Winton, M. (2006), Amplified Arctic climate change: What does surface albedo feedback have to do with it?, Geophys. Res. Lett., 33, L03701, doi:10.1029/2005GL025244. [FULL TEXT]

Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints – Masson-Delmotte et al. (2006) “Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes and with respect to pre-industrial reference simulations. For the mid-Holocene (MH, 6,000 years ago), the models are forced by changes in the Earth’s orbital parameters. The MH PMIP1 atmosphere-only simulations conducted with sea surface temperatures fixed to modern conditions show no MH consistent response for the poles, whereas the new PMIP2 coupled atmosphere–ocean climate models systematically simulate a significant MH warming both for Greenland (but smaller than ice-core based estimates) and Antarctica (consistent with the range of ice-core based range). In both PMIP1 and PMIP2, the MH annual mean changes in global temperature are negligible, consistent with the MH orbital forcing. The simulated last glacial maximum (LGM, 21,000 years ago) to pre-industrial change in global mean temperature ranges between 3 and 7°C in PMIP1 and PMIP2 model runs, similar to the range of temperature change expected from a quadrupling of atmospheric CO2 concentrations in the CMIP simulations. Both LGM and future climate simulations are associated with a polar amplification of climate change. The range of glacial polar amplification in Greenland is strongly dependent on the ice sheet elevation changes prescribed to the climate models. All PMIP2 simulations systematically underestimate the reconstructed glacial–interglacial Greenland temperature change, while some of the simulations do capture the reconstructed glacial–interglacial Antarctic temperature change. Uncertainties in the prescribed central ice cap elevation cannot account for the temperature change underestimation by climate models. The variety of climate model sensitivities enables the exploration of the relative changes in polar temperature with respect to changes in global temperatures. Simulated changes of polar temperatures are strongly related to changes in simulated global temperatures for both future and LGM climates, confirming that ice-core-based reconstructions provide quantitative insights on global climate changes.” V. Masson-Delmotte, M. Kageyama, P. Braconnot, S. Charbit, G. Krinner, C. Ritz, E. Guilyardi, J. Jouzel, A. Abe-Ouchi and M. Crucifix, et al., Climate Dynamics, Volume 26, Number 5 (2006), 513-529, DOI: 10.1007/s00382-005-0081-9. [FULL TEXT]

Polar amplification of climate change in coupled models – Holland & Bitz (2003) “The Northern Hemisphere polar amplification of climate change is documented in models taking part in the Coupled Model Intercomparison Project and in the new version of the Community Climate System Model. In particular, the magnitude, spatial distribution, and seasonality of the surface warming in the Arctic is examined and compared among the models. The range of simulated polar warming in the Arctic is from 1.5 to 4.5 times the global mean warming. While ice-albedo feedback is likely to account for much of the polar amplification, the strength of the feedback depends on numerous physical processes and parametrizations which differ considerably among the models. Nonetheless, the mean sea-ice state in the control (or present) climate is found to influence both the magnitude and spatial distribution of the high-latitude warming in the models. In particular, the latitude of the maximum warming is correlated inversely and significantly with sea-ice extent in the control climate. Additionally, models with relatively thin Arctic ice cover in the control climate tend to have higher polar amplification. An intercomparison of model results also shows that increases in poleward ocean heat transport at high latitudes and increases in polar cloud cover are significantly correlated to amplified Arctic warming. This suggests that these changes in the climate state may modify polar amplification. No significant correlation is found between polar amplification and the control climate continental ice and snow cover.” M. M. Holland and C. M. Bitz, Climate Dynamics, Volume 21, Numbers 3-4 (2003), 221-232, DOI: 10.1007/s00382-003-0332-6. [FULL TEXT]

Observationally based assessment of polar amplification of global warming – Polyakov et al. (2002) “Arctic variability is dominated by multi-decadal fluctuations. Incomplete sampling of these fluctuations results in highly variable arctic surface-air temperature (SAT) trends. Modulated by multi-decadal variability, SAT trends are often amplified relative to northern-hemispheric trends, but over the 125-year record we identify periods when arctic SAT trends were smaller or of opposite sign than northern-hemispheric trends. Arctic and northern-hemispheric air-temperature trends during the 20th century (when multi-decadal variablity had little net effect on computed trends) are similar, and do not support the predicted polar amplification of global warming. The possible moderating role of sea ice cannot be conclusively identified with existing data. If long-term trends are accepted as a valid measure of climate change, then the SAT and ice data do not support the proposed polar amplification of global warming. Intrinsic arctic variability obscures long-term changes, limiting our ability to identify complex feedbacks in the arctic climate system.” Polyakov, I. V., G. V. Alekseev, R. V. Bekryaev, U. Bhatt, R. L. Colony, M. A. Johnson, V. P. Karklin, A. P. Makshtas, D. Walsh, and A. V. Yulin (2002), Observationally based assessment of polar amplification of global warming, Geophys. Res. Lett., 29(18), 1878, doi:10.1029/2001GL011111.

Temporal and spatial variation of surface air temperature over the period of instrumental observations in the Arctic – Przybylak (2000) “A detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperatures over the period of instrumental observations in the Arctic is presented. In addition, the role of atmospheric circulation in controlling the instrumental and decadal-scale changes of air temperature in the Arctic is investigated. Mean monthly temperature and temperature anomalies data from 37 Arctic, 7 sub-Arctic and 30 grid-boxes were used for analysis. The presented analysis shows that the observed variations in air temperature in the real Arctic (defined on the basis of climatic as opposed to other criteria, e.g. astronomical or botanical) are in many aspects not consistent with the projected climatic changes computed by climatic models for the enhanced greenhouse effect. The highest temperatures since the beginning of instrumental observation occurred clearly in the 1930s and can be attributed to changes in atmospheric circulation. The second phase of contemporary global warming (after 1975) is, at most, weakly marked in the Arctic. For example, the mean rate of warming for the period 1991–1995 was 2–3 times lower in the Arctic than the global average. Temperature levels observed in Greenland in the last 10–20 years are similar to those observed in the 19th century. Increases of temperature in the Arctic are more significant in the warm half-year than in the cold half-year. This seasonal pattern in temperature change confirms the view that positive feedback mechanisms (e.g. sea-ice–albedo–temperature) as yet play only a small role in enhancing temperature in the Arctic. Hypotheses are presented to explain the lack of warming in the Arctic after 1975. It is shown that in some parts of the Arctic atmospheric circulation changes, in particular in the cold half-year, can explain up to 10–50% of the temperature variance. For Arctic temperature, the most important factor is a change in the atmospheric circulation over the North Atlantic. The influence of atmospheric circulation change over the Pacific (both in the northern and in the tropical parts) is significantly lower.” Rajmund Przybylak, International Journal of Climatology, Volume 20, Issue 6, pages 587–614, May 2000, DOI: 10.1002/(SICI)1097-0088(200005)20:63.0.CO;2-H. [FULL TEXT]

Recent Variations of Sea Ice and Air Temperature in High Latitudes – Chapman & Walsh (1993) “Feedbacks resulting from the retreat of sea ice and snow contribute to the polar amplification of the greenhouse warming projected by global climate models. A gridded sea-ice database, for which the record length is now approaching four decades for the Arctic and two decades for the Antarctic, is summarized here. The sea-ice fluctuations derived from the dataset are characterized by 1) temporal scales of several seasons to several years and 2) spatial scales of 30°–180° of longitude. The ice data are examined in conjunction with air temperature data for evidence of recent climate change in the polar regions. The arctic sea-ice variations over the past several decades are compatible with the corresponding air temperatures, which show a distinct warming that is strongest over northern land areas during the winter and spring. The temperature trends over the subarctic seas are smaller and even negative in the southern Greenland region. Statistically significant decreases of the summer extent of arctic ice are apparent in the sea-ice data, and new summer minima have been achieved three times in the past 15 years. There is no significant trend of ice extent in the Arctic during winter or in the Antarctic during any season. The seasonal and geographical changes of sea-ice coverage are consistent with the more recent greenhouse experiments performed with coupled atmosphere—ocean models.” Chapman, William L., John E. Walsh, 1993: Recent Variations of Sea Ice and Air Temperature in High Latitudes. Bull. Amer. Meteor. Soc., 74, 33–47, doi: http://dx.doi.org/10.1175/1520-0477(1993)0742.0.CO;2. [FULL TEXT]

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New research from last week 41/2012

Posted by Ari Jokimäki on October 15, 2012

It seems that this week I felt nostalgic as there are plenty of papers on past climate in this week’s batch. Perhaps I just miss the good old days when climate was all nice.


Large contribution of Canada’s glaciers to sea level rise

Accelerated contributions of Canada’s Baffin and Bylot Island glaciers to sea level rise over the past half century – Gardner et al. (2012) [FULL TEXT]

Abstract: “Canadian Arctic glaciers have recently contributed large volumes of meltwater to the world’s oceans. To place recently observed glacier wastage into a historical perspective and to determine the region’s longer-term (~50 years) contribution to sea level, we estimate mass and volume changes for the glaciers of Baffin and Bylot Islands using digital elevation models generated from airborne and satellite stereoscopic imagery and elevation postings from repeat airborne and satellite laser altimetry. In addition, we update existing glacier mass change records from GRACE satellite gravimetry to cover the period from 2003 to 2011. Using this integrated approach, we find that the rate of mass loss from the region’s glaciers increased from 11.1 ± 3.4 Gt a−1 (271 ± 84 kg m−2 a−1) for the period 1963–2006 to 23.8 ± 6.1 Gt a−1(581 ± 149 kg m−2 a−1) for the period 2003–2011. The doubling of the rate of mass loss is attributed to higher temperatures in summer with little change in annual precipitation. Through both direct and indirect effects, changes in summer temperatures accounted for 70–98% of the variance in the rate of mass loss, to which the Barnes Ice Cap was found to be 1.7 times more sensitive than either the Penny Ice Cap or the region’s glaciers as a whole. This heightened sensitivity is the result of a glacier hypsometry that is skewed to lower elevations, which are shown to have a higher mass change sensitive to temperature compared to glacier surfaces at higher elevations. Between 2003 and 2011 the glaciers of Baffin and Bylot Islands contributed 0.07 ± 0.02 mm a−1 to sea level rise accounting for 16% of the total contribution from glaciers outside of Greenland and Antarctica, a rate much higher than the longer-term average of 0.03 ± 0.01 mm a−1 (1963 to 2006).”

Citation: Gardner, A., Moholdt, G., Arendt, A., and Wouters, B.: Accelerated contributions of Canada’s Baffin and Bylot Island glaciers to sea level rise over the past half century, The Cryosphere, 6, 1103-1125, doi:10.5194/tc-6-1103-2012, 2012.


Observed interannual variability of the Atlantic meridional overturning circulation

Observed interannual variability of the Atlantic meridional overturning circulation at 26.5°N – McCarthy et al. (2012) [FULL TEXT]

Abstract: “The Atlantic meridional overturning circulation (MOC) plays a critical role in the climate system and is responsible for much of the heat transported by the ocean. A mooring array, nominally at 26°N between the Bahamas and the Canary Islands, deployed in Apr 2004 provides continuous measurements of the strength and variability of this circulation. With seven full years of measurements, we now examine the interannual variability of the MOC. While earlier results highlighted substantial seasonal and shorter timescale variability, there had not been significant interannual variability. The mean MOC from 1 Apr 2004 to the 31 March 2009 was 18.5 Sv with the annual means having a standard deviation of only 1.0 Sv. From 1 April 2009 to 31 March 2010, the annually averaged MOC strength was just 12.8 Sv, representing a 30% decline. This downturn persisted from early 2009 to mid-2010. We show that the cause of the decline was not only an anomalous wind-driven event from Dec 2009–Mar 2010 but also a strengthening of the geostrophic flow. In particular, the southward flow in the top 1100 m intensified, while the deep southward return transport—particularly in the deepest layer from 3000–5000 m—weakened. This rebalancing of the transport from the deep overturning to the upper gyre has implications for the heat transported by the Atlantic.”

Citation: McCarthy, G., E. Frajka-Williams, W. E. Johns, M. O. Baringer, C. S. Meinen, H. L. Bryden, D. Rayner, A. Duchez, C. Roberts, and S. A. Cunningham (2012), Observed interannual variability of the Atlantic meridional overturning circulation at 26.5°N, Geophys. Res. Lett., 39, L19609, doi:10.1029/2012GL052933.


Climate change threatens Lake Tahoe’s most highly valued characteristics

The response of Lake Tahoe to climate change – Sahoo et al. (2012) [FULL TEXT]

Abstract: “Meteorology is the driving force for lake internal heating, cooling, mixing, and circulation. Thus continued global warming will affect the lake thermal properties, water level, internal nutrient loading, nutrient cycling, food-web characteristics, fish-habitat, aquatic ecosystem, and other important features of lake limnology. Using a 1-D numerical model—the Lake Clarity Model (LCM) —together with the down-scaled climatic data of the two emissions scenarios (B1 and A2) of the Geophysical Fluid Dynamics Laboratory (GFDL) Global Circulation Model, we found that Lake Tahoe will likely cease to mix to the bottom after about 2060 for A2 scenario, with an annual mixing depth of less than 200 m as the most common value. Deep mixing, which currently occurs on average every 3–4 years, will (under the GFDL B1 scenario) occur only four times during 2061 to 2098. When the lake fails to completely mix, the bottom waters are not replenished with dissolved oxygen and eventually dissolved oxygen at these depths will be depleted to zero. When this occurs, soluble reactive phosphorus (SRP) and ammonium-nitrogen (both biostimulatory) are released from the deep sediments and contribute approximately 51 % and 14 % of the total SRP and dissolved inorganic nitrogen load, respectively. The lake model suggests that climate change will drive the lake surface level down below the natural rim after 2085 for the GFDL A2 but not the GFDL B1 scenario. The results indicate that continued climate changes could pose serious threats to the characteristics of the Lake that are most highly valued. Future water quality planning must take these results into account.”

Citation: G. B. Sahoo, S. G. Schladow, J. E. Reuter, R. Coats, M. Dettinger, J. Riverson, B. Wolfe and M. Costa-Cabral, Climatic Change, 2012, DOI: 10.1007/s10584-012-0600-8.


Using old weather observations to validate past climate reconstructions

Constraining the temperature history of the past millennium using early instrumental observations – Brohan et al. (2012) [FULL TEXT]

Abstract: “The current assessment that twentieth-century global temperature change is unusual in the context of the last thousand years relies on estimates of temperature changes from natural proxies (tree-rings, ice-cores, etc.) and climate model simulations. Confidence in such estimates is limited by difficulties in calibrating the proxies and systematic differences between proxy reconstructions and model simulations. As the difference between the estimates extends into the relatively recent period of the early nineteenth century it is possible to compare them with a reliable instrumental estimate of the temperature change over that period, provided that enough early thermometer observations, covering a wide enough expanse of the world, can be collected. One organisation which systematically made observations and collected the results was the English East India Company (EEIC), and their archives have been preserved in the British Library. Inspection of those archives revealed 900 log-books of EEIC ships containing daily instrumental measurements of temperature and pressure, and subjective estimates of wind speed and direction, from voyages across the Atlantic and Indian Oceans between 1789 and 1834. Those records have been extracted and digitised, providing 273 000 new weather records offering an unprecedentedly detailed view of the weather and climate of the late eighteenth and early nineteenth centuries. The new thermometer observations demonstrate that the large-scale temperature response to the Tambora eruption and the 1809 eruption was modest (perhaps 0.5 °C). This provides an out-of-sample validation for the proxy reconstructions – supporting their use for longer-term climate reconstructions. However, some of the climate model simulations in the CMIP5 ensemble show much larger volcanic effects than this – such simulations are unlikely to be accurate in this respect.”

Citation: Brohan, P., Allan, R., Freeman, E., Wheeler, D., Wilkinson, C., and Williamson, F.: Constraining the temperature history of the past millennium using early instrumental observations, Clim. Past, 8, 1551-1563, doi:10.5194/cp-8-1551-2012, 2012.


How ice sheets and climate affect each other

Modelling large-scale ice-sheet–climate interactions following glacial inception – Gregory et al. (2012) [FULL TEXT]

Abstract: “We have coupled the FAMOUS global AOGCM (atmosphere-ocean general circulation model) to the Glimmer thermomechanical ice-sheet model in order to study the development of ice-sheets in north-east America (Laurentia) and north-west Europe (Fennoscandia) following glacial inception. This first use of a coupled AOGCM–ice-sheet model for a study of change on long palæoclimate timescales is made possible by the low computational cost of FAMOUS, despite its inclusion of physical parameterisations similar in complexity to higher-resolution AOGCMs. With the orbital forcing of 115 ka BP, FAMOUS–Glimmer produces ice caps on the Canadian Arctic islands, on the north-west coast of Hudson Bay and in southern Scandinavia, which grow to occupy the Keewatin region of the Canadian mainland and all of Fennoscandia over 50 ka. Their growth is eventually halted by increasing coastal ice discharge. The expansion of the ice-sheets influences the regional climate, which becomes cooler, reducing the ablation, and ice accumulates in places that initially do not have positive surface mass balance. The results suggest the possibility that the glaciation of north-east America could have begun on the Canadian Arctic islands, producing a regional climate change that caused or enhanced the growth of ice on the mainland. The increase in albedo (due to snow and ice cover) is the dominant feedback on the area of the ice-sheets and acts rapidly, whereas the feedback of topography on SMB does not become significant for several centuries, but eventually has a large effect on the thickening of the ice-sheets. These two positive feedbacks are mutually reinforcing. In addition, the change in topography perturbs the tropospheric circulation, producing some reduction of cloud, and mitigating the local cooling along the margin of the Laurentide ice-sheet. Our experiments demonstrate the importance and complexity of the interactions between ice-sheets and local climate.”

Citation: Gregory, J. M., Browne, O. J. H., Payne, A. J., Ridley, J. K., and Rutt, I. C.: Modelling large-scale ice-sheet–climate interactions following glacial inception, Clim. Past, 8, 1565-1580, doi:10.5194/cp-8-1565-2012, 2012.


Planetary fertility reconstruction of the past 400,000 years

Planetary fertility during the past 400 ka based on the triple isotope composition of O2 in trapped gases from the Vostok ice core – Blunier et al. (2012) [FULL TEXT]

Abstract: “The productivity of the biosphere leaves its imprint on the isotopic composition of atmospheric oxygen. Ultimately, atmospheric oxygen, through photosynthesis, originates from seawater. Fractionations during the passage from seawater to atmospheric O2 and during respiration affect δ17O approximately half as much as δ18O. An “anomalous” (also termed mass independent) fractionation process changes δ17O about 1.7 times as much as δ18O during isotope exchange between O2 and CO2 in the stratosphere. The relative rates of biological O2 production and stratospheric processing determine the relationship between δ17O and δ18O of O2 in the atmosphere. Variations of this relationship thus allow us to estimate changes in the rate of O2 production by photosynthesis versus the rate of O2–CO2 isotope exchange in the stratosphere. However, the analysis of the 17O anomaly is complicated because each hydrological and biological process fractionates δ17O and δ18O in slightly different proportions. In this study we present O2 isotope data covering the last 400 ka (thousand years) from the Vostok ice core. We reconstruct oxygen productivities from the triple isotope composition of atmospheric oxygen with a box model. Our steady state model for the oxygen cycle takes into account fractionation during photosynthesis and respiration by the land and ocean biosphere, fractionation during the hydrologic cycle, and fractionation when oxygen passes through the stratosphere. We consider changes of fractionation factors linked to climate variations, taking into account the span of estimates of the main factors affecting our calculations. We find that ocean oxygen productivity was within 20% of the modern value throughout the last 400 ka. Given the presumed reduction in terrestrial oxygen productivity, the total oxygen production during glacials was likely reduced.”

Citation: Blunier, T., Bender, M. L., Barnett, B., and von Fischer, J. C.: Planetary fertility during the past 400 ka based on the triple isotope composition of O2 in trapped gases from the Vostok ice core, Clim. Past, 8, 1509-1526, doi:10.5194/cp-8-1509-2012, 2012.


Northern Hemisphere June snow cover extent decreases faster than Arctic sea ice

Spring snow cover extent reductions in the 2008–2012 period exceeding climate model projections – Derksen & Brown (2012)

Abstract: “Analysis of Northern Hemisphere spring terrestrial snow cover extent (SCE) from the NOAA snow chart Climate Data Record (CDR) for the April to June period (when snow cover is mainly located over the Arctic) has revealed statistically significant reductions in May and June SCE. Successive records for the lowest June SCE have been set each year for Eurasia since 2008, and in 3 of the past 5 years for North America. The rate of loss of June snow cover extent between 1979 and 2011 (−17.8% decade−1) is greater than the loss of September sea ice extent (−10.6% decade−1) over the same period. Analysis of Coupled Model Intercomparison Project Phase 5 (CMIP5) model output shows the marked reductions in June SCE observed since 2005 fall below the zone of model consensus defined by +/−1 standard deviation from the multi-model ensemble mean.”

Citation: Derksen, C. and R. Brown (2012), Spring snow cover extent reductions in the 2008–2012 period exceeding climate model projections, Geophys. Res. Lett., 39, L19504, doi:10.1029/2012GL053387.


Antarctic Peninsula glacier surfaces are lowering

Multi-decadal glacier surface lowering in the Antarctic Peninsula – Kunz et al. (2012)

Abstract: “From approximately 400 glaciers of the western Antarctic Peninsula, no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained. We seek to address this shortcoming by using surface elevations from USGS and BAS airborne (1948–2005) and ASTER spaceborne (2001–2010) stereo imagery, combined by using a rigorous semi-automated registration approach, to determine multi-decadal glacier surface elevation changes in the western Antarctic Peninsula for 12 glaciers. All observed glaciers show near-frontal surface lowering and an annual mean lowering rate of 0.28 ± 0.03 m/yr at the lower portion of the glaciers during the ∼4 decades following the mid-1960s, with higher rates for the glaciers in the north-west parts of the Antarctic Peninsula. Increased lowering of up to 0.6 m/yr can be observed since the 1990s, in close correspondence to increased atmospheric positive degree days. In all cases, surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude. This lowering may have been at least partially compensated for by increased high-altitude accumulation.”

Citation: Kunz, M., M. A. King, J. P. Mills, P. E. Miller, A. J. Fox, D. G. Vaughan, and S. H. Marsh (2012), Multi-decadal glacier surface lowering in the Antarctic Peninsula, Geophys. Res. Lett., 39, L19502, doi:10.1029/2012GL052823.


Freshwater flux from Greenland increasing faster than expected

Recent large increases in freshwater fluxes from Greenland into the North Atlantic – Bamber et al. (2012)

Abstract: “Freshwater (FW) fluxes from river runoff and precipitation minus evaporation for the pan Arctic seas are relatively well documented and prescribed in ocean GCMs. Fluxes from Greenland on the other hand are generally ignored altogether, despite their potential impacts on ocean circulation and marine biology. Here, we present a reconstruction of the spatially distributed FW flux from Greenland for 1958-2010. We find a modest increase into the Arctic Ocean during this period. Fluxes into the Irminger Basin, however, have increased by fifty percent (6.3{plus minus}0.5 km3 yr-2) in less than twenty years. This greatly exceeds previous estimates. For the ice sheet as a whole the rate of increase since 1992 is 16.9{plus minus}1.8 km3 yr-2. The cumulative FW anomaly since 1995 is 3200{plus minus}358 km3, which is about a third of the magnitude of the Great Salinity Anomaly (GSA) of the 1970s. If this trend continues into the future, the anomaly will exceed that of the GSA by about 2025.”

Citation: Bamber, J. L., M. R. van den Broeke, J. Ettema, J. T. M. Lenaerts, and E. Rignot (2012), Recent large increases in freshwater fluxes from Greenland into the North Atlantic, Geophys. Res. Lett., doi:10.1029/2012GL052552.


Hadley Cell might contract rapidly when CO2 reaches 1000 ppm

New thoughts about the cretaceous climate and oceans – Hay & Floegel (2012)

Abstract: “Several new discoveries suggest that the climate of the Cretaceous may have been more different from that of today than has been previously supposed. Detailed maps of climate sensitive fossils and sediments compiled by Nicolai Chumakov and his colleagues in Russia indicate widespread aridity in the equatorial region during the Early Cretaceous. The very warm ocean temperatures postulated for the Mid-Cretaceous by some authors would likely have resulted in unacceptable heat stress for land plants at those latitudes, however, and may be flawed. Seasonal reversals of the atmospheric pressure systems in the Polar Regions are an oversimplification. However, seasonal pressure difference between 30° and 60° latitude become quite pronounced, being more than 25 hPa in winter and less than 10 hPa in summer. This results in inconstant winds, affecting the development of the gyre-limiting frontal systems that control modern ocean circulation. The idea of Hasegawa et al. (2011) who suggest a drastic reduction in the size of the Hadley cells during the warm Cretaceous greenhouse is supported by several numerical climate simulations. Rapid contraction of the Hadley cell such that its sinking dry air occurs at 15° N latitude rather than 30° N is proposed to occur at a threshold of 1,000 ppmv CO2 in the atmosphere. This change will probably be reached in the next century.”

Citation: William W. Hay, Sascha Floegel, Earth-Science Reviews, http://dx.doi.org/10.1016/j.earscirev.2012.09.008.


Other studies from last week

Vegetation and climatic changes of SW China in response to the uplift of Tibetan Plateau – Zhang et al. (2012)

Paleo-climate of the central European uplands during the last glacial maximum based on glacier mass-balance modeling – Heyman et al. (2012)

Relationship between the expansion of drylands and the intensification of Hadley circulation during the late twentieth century – Shin et al. (2012)

Urban heat island in a coastal urban area in northern Spain – Acero et al. (2012)

Mixed nonlinear regression for modelling historical temperatures in Central–Southern Italy – Diodato et al. (2012)

The global signature of the ENSO and SST-like fields – Varotsos (2012)

Phenological changes of oceanic phytoplankton in the 1980s and 2000s as revealed by remotely sensed ocean-color observations – D’Ortenzio et al. (2012)

How warming and steric sea level rise relate to cumulative carbon emissions – Williams et al. (2012)

Sensitivity to Glacial Forcing in the CCSM4 – Brady et al. (2012)

Temporal scales of tropospheric CO2, precipitation, and ecosystem responses in the central Great Plains – Cochran & Brunsell (2012)

Isotopic and lithologic variations of one precisely-dated stalagmite across the Medieval/LIA period from Heilong Cave, central China – Cui et al. (2012) [FULL TEXT]

Sea surface temperature variability in the Pacific sector of the Southern Ocean over the past 700 kyr – Ho et al. (2012)

Optimal temperature for malaria transmission is dramatically lower than previously predicted – Mordecai et al. (2012)

Improving spatial temperature estimates by resort to time autoregressive processes – Joly et al. (2012)

Extreme ozone depletion in the 2010–2011 Arctic winter stratosphere as observed by MIPAS/ENVISAT using a 2-D tomographic approach – Arnone et al. (2012) [FULL TEXT]

The recent shift in early summer Arctic atmospheric circulation – Overland et al. (2012)

How should we grow cities to minimise their biodiversity impacts? – Sushisnky et al. (2012)

A longer climate memory carried by soil freeze–thaw processes in Siberia – Matsumura & Yamazaki (2012) [FULL TEXT]

CO2 fertilization and enhanced drought resistance in Greek firs from Cephalonia Island, Greece – Koutavas (2012)

Sensitivity and response of Bhutanese glaciers to atmospheric warming – Rupper et al. (2012)


CLASSIC OF THE WEEK: Shapley (1921)

Note on a Possible Factor in Changes of Geological Climate – Shapley (1921) [FULL TEXT]

Abstract: No abstract.

Citation: Harlow Shapley, The Journal of Geology, Vol. 29, No. 6 (Sep. – Oct., 1921) (pp. 502-504).


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 1 Comment »

New research from last week 40/2012

Posted by Ari Jokimäki on October 8, 2012

Sun is the fireball in the sky that controlled Earth’s climate until mankind took the control. Sun still has some regional tricks, but in order to take back the control of global climate in near future, Sun would need to do some special tricks. Not Sun-related studies this week deal with climate scepticism, cloud height, methane emissions, ocean temperatures, Antarctic glaciers, 2011 sea level drop, ball lightning, surface specific humidity, model predictions, permafrost, past climate, European and East Asian summer temperatures, and some other things. There’s 15 studies + another 17 in other papers section, and I only include here a small fraction of all climate related papers. It was a rather busy week in climate science.


Solar forcing of Europe summer temperatures during last 1000 years

Mechanisms for European summer temperature response to solar forcing over the last millennium – Swingedouw et al. (2012) [FULL TEXT]

Abstract: “A simulation of the last millennium is compared to a recent spatio-temporal reconstruction of summer temperature over Europe. The focus is on the response to solar forcing over the pre-industrial era. Although the correlation between solar forcing and the reconstruction remains small, the spatial regression over solar forcing shows statistically significant regions. The meridional pattern of this regression is found to be similar in the model and in the reconstruction. This pattern exhibits a large warming over Northern and Mediterranean Europe and a lesser amplitude response over Central and Eastern Europe. The mechanisms explaining this pattern in the simulation are mainly related to evapotranspiration fluxes. It is shown that the evapotranspiration is larger in summer over Central and Eastern Europe when solar forcing increases, while it decreases over the Mediterranean area. The explanation for the evapotranspiration increase over Central and Eastern Europe is found in the increase of winter precipitation there, leading to a soil moisture increase in spring. As a consequence, the evapotranspiration is larger in summer, which leads to an increase in cloud cover over this region, reducing the surface shortwave flux there and leading to less warming. Over the Mediterranean area, the surface shortwave flux increases with solar forcing, the soil becomes dryer and the evapotranspiration is reduced in summer leading to a larger increase in temperature. This effect appears to be overestimated in the model as compared to the reconstruction. Finally, the warming of Northern Europe is related to the albedo feedback due to sea-ice cover retreat with increasing solar forcing.”

Citation: Swingedouw, D., Terray, L., Servonnat, J., and Guiot, J.: Mechanisms for European summer temperature response to solar forcing over the last millennium, Clim. Past, 8, 1487-1495, doi:10.5194/cp-8-1487-2012, 2012.


Solar effects on cloud cover are seen in some regions but are not visible at the global level

Persistent solar signatures in cloud cover: spatial and temporal analysis – Voiculescu & Usoskin (2012) [FULL TEXT]

Abstract: “A consensus regarding the impact of solar variability on cloud cover is far from being reached. Moreover, the impact of cloud cover on climate is among the least understood of all climate components. This motivated us to analyze the persistence of solar signals in cloud cover for the time interval 1984–2009, covering two full solar cycles. A spatial and temporal investigation of the response of low, middle and high cloud data to cosmic ray induced ionization (CRII) and UV irradiance (UVI) is performed in terms of coherence analysis of the two signals. For some key geographical regions the response of clouds to UVI and CRII is persistent over the entire time interval indicating a real link. In other regions, however, the relation is not consistent, being intermittent or out of phase, suggesting that some correlations are spurious. The constant in phase or anti-phase relationship between clouds and solar proxies over some regions, especially for low clouds with UVI and CRII, middle clouds with UVI and high clouds with CRII, definitely requires more study. Our results show that solar signatures in cloud cover persist in some key climate-defining regions for the entire time period and supports the idea that, if existing, solar effects are not visible at the global level and any analysis of solar effects on cloud cover (and, consequently, on climate) should be done at the regional level.”

Citation: M Voiculescu and I Usoskin 2012 Environ. Res. Lett. 7 044004 doi:10.1088/1748-9326/7/4/044004.


News coverage of climate scepticism is mostly limited to the USA and the UK

Cross-national comparison of the presence of climate scepticism in the print media in six countries, 2007–10 – Painter & Ashe (2012) [FULL TEXT]

Abstract: “Previous academic research on climate scepticism has tended to focus more on the way it has been organized, its tactics and its impact on policy outputs than on its prevalence in the media. Most of the literature has centred on the USA, where scepticism first appeared in an organized and politically effective form. This letter contrasts the way climate scepticism in its different forms is manifested in the print media in the USA and five other countries (Brazil, China, France, India and the UK), in order to gain insight into how far the US experience of scepticism is replicated in other countries. It finds that news coverage of scepticism is mostly limited to the USA and the UK; that there is a strong correspondence between the political leaning of a newspaper and its willingness to quote or use uncontested sceptical voices in opinion pieces; and that the type of sceptics who question whether global temperatures are warming are almost exclusively found in the US and UK newspapers. Sceptics who challenge the need for robust action to combat climate change also have a much stronger presence in the media of the same two countries.”

Citation: James Painter and Teresa Ashe 2012 Environ. Res. Lett. 7 044005 doi:10.1088/1748-9326/7/4/044005.


Positive trend in cloud height globally

On global changes in effective cloud height – Evan & Norris (2012)

Abstract: “Measurements by the Multiangle Imaging SpectroRadiometer (MISR) instrument exhibit a decreasing trend in global mean effective cloud top height (2000–2011). Here we show that this trend is likely related to an artifact in the data present during the early years of the MISR mission that caused a systematic reduction in the number of retrievals of clouds at lower elevations relative to clouds at higher elevations. After the application of a post-hoc method for removing the bias associated with missing retrievals the MISR effective cloud height anomalies exhibit a positive trend over time.”

Citation: Evan, A. T. and J. R. Norris (2012), On global changes in effective cloud height, Geophys. Res. Lett., 39, L19710, doi:10.1029/2012GL053171.


Global anthropogenic methane emissions 2005–2030

Global anthropogenic methane emissions 2005–2030: technical mitigation potentials and costs – Höglund-Isaksson (2012) [FULL TEXT]

Abstract: “This paper presents estimates of current and future global anthropogenic methane emissions, their technical mitigation potential and associated costs for the period 2005 to 2030. The analysis uses the GAINS model framework to estimate emissions, mitigation potentials and costs for all major sources of anthropogenic methane for 83 countries/regions, which are aggregated to produce global estimates. Global emissions are estimated at 323 Mt methane in 2005, with an expected increase to 414 Mt methane in 2030. The technical mitigation potential is estimated at 195 Mt methane in 2030, whereof about 80 percent is found attainable at a marginal cost less than 20 Euro t−1 CO2eq when using a social planner cost perspective. With a private investor cost perspective, the corresponding fraction is only 30 percent. Major uncertainty sources in emission estimates are identified and discussed.”

Citation: Höglund-Isaksson, L.: Global anthropogenic methane emissions 2005–2030: technical mitigation potentials and costs, Atmos. Chem. Phys., 12, 9079-9096, doi:10.5194/acp-12-9079-2012, 2012.


Two independent observing networks show that global near surface ocean has warmed since 1900

Consistent near-surface ocean warming since 1900 in two largely independent observing networks – Gouretski et al. (2012)

Abstract: “We compare historical global temperature time series, based on bias-adjusted sea-surface temperatures with independent temperature time series, for the upper 20 meter layer of the ocean based on the latest update of an historical hydrographic profile data set. Despite the two underlying data sets being different in number of data points, instrumentation and applied adjustments, both of the time series are consistent in showing an overall warming since 1900. We also extend records of temperature change in the upper 400 m back to 1900. Noting that the geographic coverage is limited prior to 1950, the temperature change in the 0–400 m layer is characterized by two periods of temperature increase between 1900 and 1940–45 and between 1970 and 2003, separated by a period of little change.”

Citation: Gouretski, V., J. Kennedy, T. Boyer, and A. Köhl (2012), Consistent near-surface ocean warming since 1900 in two largely independent observing networks, Geophys. Res. Lett., 39, L19606, doi:10.1029/2012GL052975.


Accelerated thinning of Antarctic glaciers on the coast of the Amundsen Sea

Dynamic thinning of Antarctic glaciers from along-track repeat radar altimetry – Flament & Rémy (2012)

Abstract: “Since 2002, the Envisat radar altimeter has measured the elevation of the Antarctic ice sheet with a repeat cycle of 35 days. This long and regular time series is processed using an along-track algorithm to depict in detail the spatial and temporal pattern of elevation change for the whole ice sheet. We use this dataset to examine the spatial and temporal pattern of Pine Island Glacier (PIG) thinning and compare it to the neighbouring glaciers. We also examine additional areas, especially in East Antarctica whose mass balance is poorly known. One advantage of the finer along-track spacing of measurements is that it reveals places of dynamic thinning in regions of rapid ice flow. We observe the acceleration of thinning on PIG. Over the entire basin, the volume loss increased from 7 km3 a-1 during 2002-06 to ∼48 km3 a-1 during 2006-10. We also observe accelerated thinning on the lower tens of kilometres of Thwaites Glacier, with a mean thinning of 0.18 m a-1 over its entire basin during our observation period. We confirm the dynamic thinning of Totten Glacier but we do not detect significantly accelerated thinning on any glacier elsewhere than on the coast of the Amundsen Sea.”

Citation: Flament, Thomas; Rémy, Frédérique, Journal of Glaciology, Volume 58, Number 211, September 2012 , pp. 830-840(11), DOI: http://dx.doi.org/10.3189/2012JoG11J118.


Sea level drop in 2011 was mainly caused by La Nina’s effect on water exchange between ocean and land

The 2011 La Niña: So strong, the oceans fell – Boening et al. (2012)

Abstract: “Global mean sea level (GMSL) dropped by 5 mm between the beginning of 2010 and mid 2011. This drop occurred despite the background rate of rise, 3 mm per year, which dominates most of the 18-year record observed by satellite altimeters. Using a combination of satellite and in situ data, we show that the decline in ocean mass, which explains the sea level drop, coincides with an equivalent increase in terrestrial water storage, primarily over Australia, northern South America, and Southeast Asia. This temporary shift of water from the ocean to land is closely related to the transition from El Niño conditions in 2009/10 to a strong 2010/11 La Niña, which affected precipitation patterns world-wide.”

Citation: Boening, C., J. K. Willis, F. W. Landerer, R. S. Nerem, and J. Fasullo (2012), The 2011 La Niña: So strong, the oceans fell, Geophys. Res. Lett., 39, L19602, doi:10.1029/2012GL053055.


Watching the birth of ball lightning

Birth of ball lightning – Lowke et al. (2012)

Abstract: “Many observations of ball lightning report a ball of light, about 10 cm in diameter, moving at about walking speed, lasting up to 20 s and frequently existing inside of houses and even aeroplanes. The present paper reports detailed observations of the initiation or birth of ball lightning. In two cases, navigation crew of aircraft saw ball lightning form at the windscreen inside the cockpit of their planes. In the first case, the ball lightning occurred during a thunderstorm, with much lightning activity outside of the plane. In the second case, large “horns” of electrical corona were seen outside of the plane at the surface of the radome, just prior to the formation of the ball lightning. A third case reports ball lightning formed inside of a house, during a thunderstorm, at a closed glass window. It is proposed, based on two-dimensional calculations of electron and ion transport, that ball lightning in these cases is driven and formed by atmospheric ions impinging and collecting on the insulating surface of the glass or Perspex windows. This surface charge can produce electric fields inside of the cockpit or room sufficient to sustain an electric discharge. Charges of opposite sign to those outside of the window accumulate on the inside surface of the glass, leaving a ball of net charge moving inside of the cockpit or room to produce a pulsed discharge on a microsecond time scale.”

Citation: Lowke, J. J., D. Smith, K. E. Nelson, R. W. Crompton, and A. B. Murphy (2012), Birth of ball lightning, J. Geophys. Res., 117, D19107, doi:10.1029/2012JD017921.


Effect of human actions is detectable in Mediterranean surface specific humidity trends

Anthropogenic forcing is a plausible explanation for the observed surface specific humidity trends over the Mediterranean area – Barkhordarian et al. (2012)

Abstract: “We investigate whether the observed surface specific humidity (q) trends over the Mediterranean region in the period 1974–2003 are consistent with climate model (CMIP3, CMIP5) simulations of q in response to anthropogenic forcing (Greenhouse gas and sulphate aerosols). The natural (internal) variability is estimated using 6,000-year of pre-industrial control simulations. With the exception of winter, the increases in annual and seasonal q over this region are very unlikely (with less than 1%chance) due to natural (internal) variability or natural forcing alone. Using several climate models and ensemble means, we demonstrate that the large-scale component (spatial-mean trend) of the anthropogenic forcing is detectable (at 1% level) in the annual and seasonal trends of q (except winter). However, the smaller-scale component (spatial anomalies about the mean trend) of the anthropogenic signal is detectable only in warm seasons (spring and summer). We further show that the spread of projected trends based on the A1B scenario derived from 13 CMIP3 models encompasses the observed area-averaged trend in q. This may imply that the observed trends of surface humidity, which is an important factor in human thermal comfort, serves as an illustration of plausible future expected change in the region.”

Citation: Barkhordarian, A., H. von Storch, and E. Zorita (2012), Anthropogenic forcing is a plausible explanation for the observed surface specific humidity trends over the Mediterranean area, Geophys. Res. Lett., 39, L19706, doi:10.1029/2012GL053026.


Adjusting for model deficiencies in decadal predictions of global climate

Statistical adjustment of decadal predictions in a changing climate – Kharin et al. (2012)

Abstract: “A method for post-processing decadal predictions from global climate models that accounts for model deficiencies in representing climate trends is proposed and applied to decadal predictions of annual global mean temperature from the Canadian Centre for Climate Modelling and Analysis climate model. The method, which provides a time-dependent trend adjustment, reduces residual drifts that remain after applying the standard time-independent bias correction when the modelled and observed long-term trends differ. Initialized predictions and uninitialized simulations that share common specified external forcing are analyzed. Trend adjustment substantially reduces forecast errors in both cases and initialization further enhances skill, particularly for the first forecast year.”

Citation: Kharin, V. V., G. J. Boer, W. J. Merryfield, J. F. Scinocca, and W.-S. Lee (2012), Statistical adjustment of decadal predictions in a changing climate, Geophys. Res. Lett., 39, L19705, doi:10.1029/2012GL052647.


How much permafrost will be lost during 21st century?

Analysis of permafrost thermal dynamics and response to climate change in the CMIP5 Earth System Models – Koven et al. (2012)

Abstract:“We analyze global climate model predictions of soil temperature (from the Coupled Model Intercomparison Project 5 (CMIP5) database) to assess the models’ representation of current-climate soil thermal dynamics, and their predictions of permafrost thaw during the 21st century. We compare the models’ predictions to observations of active layer thickness, air temperature, and soil temperature, and to theoretically-expected relationships between active layer thickness and air temperature annual mean and seasonal cycle amplitude. Models show a wide range of current permafrost areas, active layer statistics (cumulative distributions, correlations with mean annual air temperature and amplitude of seasonal air temperature cycle), and ability to accurately model the coupling between soil and air temperatures at high latitudes. Many of the between-model differences can be traced to differences in the coupling between either near-surface air and shallow soil temperatures, or between shallow and deeper (1m) soil temperatures, which in turn reflect differences in snow physics and soil hydrology. We compare the models to observational datasets to benchmark the permafrost-relevant physics of the models. The models show a wide range of predictions for permafrost loss: 2-66% for RCP2.6, 15-87% for RCP4.5, and 30-99% for RCP8.5. Normalizing the amount of permafrost loss by the amount of high-latitude warming in the RCP4.5 scenario, the models predict an absolute loss of 1.6 ± 0.7 million km2 permafrost °C−1 high-latitude warming, or a fractional loss of 6-29% °C−1.”

Citation: Charles D. Koven, William J. Riley, and Alex Stern, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00228.1.


Climate reconstruction of past 14000 years from East Africa

Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa – Berke et al. (2012)

Abstract: “New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ∼14,000 year record of climate variability from Lake Victoria, East Africa, the world’s second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific δD of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific δ13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ∼10–9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The δ13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the interhemispheric contrast gradient minima. We interpret a shift in conditions at the Younger Dryas to indicate a limited switch in insolation-dominated control on climate of the Lake Victoria region, to remote teleconnections with the coupled Atlantic and Pacific climate system.”

Citation: Melissa A. Berke, Thomas C. Johnson, Josef P. Werne, Kliti Grice, Stefan Schouten, Jaap S. Sinninghe Damsté, Quaternary Science Reviews, Volume 55, 8 November 2012, Pages 59–74, http://dx.doi.org/10.1016/j.quascirev.2012.08.014.


European summer temperature variability might increase in the future

Changes in European summer temperature variability revisited – Fischer et al. (2012)

Abstract: “Summer temperature variability has been projected to increase in Central Europe in response to anthropogenic greenhouse gas forcing. Based on an unprecedented set of global and regional climate models from the ENSEMBLES project, we assess the robustness of these projections on interannual to daily time scales. In comparison to previous analyses using PRUDENCE simulations, we find a more diverse climate change signal for interannual summer temperature variability and a clear dependence upon present-day model performance. Models that realistically represent present-day variability, tend to consistently project increasing interannual variability at the end of the 21st century. We demonstrate that the partitioning of latent and sensible heat fluxes controlled by soil moisture is crucial to understand the projected changes across the multi-model experiment. The projected increase in daily summer temperature variability is more robust and consistently simulated by all models. Likewise, all models consistently project reduced daily temperature variability in winter. Thus, it is a robust signal across the entire ensemble that in summer and south-central Europe hot extremes warm stronger than the mean, and in winter and northern Europe cold extremes warm stronger than mean temperatures.”

Citation: Fischer, E. M., J. Rajczak, and C. Schär (2012), Changes in European summer temperature variability revisited, Geophys. Res. Lett., 39, L19702, doi:10.1029/2012GL052730.


Why is there a summer cooling trend in East Asia?

Influences of external forcing changes on the summer cooling trend over East Asia – He et al. (2012)

Abstract: “Observations indicate a surface cooling trend during the East Asian summer in recent decades, against a background of global warming. This cooling trend is re-examined using station data from 1951 to 2007, and atmospheric general circulation model (AGCM) simulations are performed to investigate the possible influence of changes in external forcing. The numerical experiments are designed to investigate the effects of four types of external forcing: greenhouse gases (GHGs), Total Solar Irradiance (TSI), ozone, and the direct effects of aerosols. Results indicate that external forcing contributes to the cooling trend over East Asia. Furthermore, GHGs, and to a lesser degree the direct effects of aerosols, are the main contributors to the cooling trend. The possible linkages between the external forcings and the cooling trend are discussed.”

Citation: Bian He, Qing Bao, Jiandong Li, Guoxiong Wu, Yimin Liu, Xiaocong Wang and Zhaobo Sun, Climatic Change, 2012, DOI: 10.1007/s10584-012-0592-4.


Other studies from last week

Modeling plant species distributions under future climates: how fine-scale do climate projections need to be? – Franklin et al. (2012)

Clay record of climate change since the mid-Pleistocene in Jiujiang, south China – Hong et al. (2012)

Modeling the climatic effects of large explosive volcanic eruptions – Timmreck (2012)

Rapid sea-level rise – Cronin (2012)

Changing controls on oceanic radiocarbon: New insights on shallow-to-deep ocean exchange and anthropogenic CO2 uptake – Graven et al. (2012)

Heliospheric modulation of galactic cosmic rays during grand solar minima: Past and future variations – Owens et al. (2012)

The vegetation cover of New Zealand at the Last Glacial Maximum – Newnham et al. (2012)

Distribution of methane in the tropical upper troposphere measured by CARIBIC and CONTRAIL aircraft – Schuck et al. (2012)

Ocean acidification and its impacts: an expert survey – Gattuso et al. (2012)

Effects of observed and experimental climate change on terrestrial ecosystems in northern Canada: results from the Canadian IPY program – Henry et al. (2012) [FULL TEXT]

Modelling the impact of climate change on Pacific skipjack tuna population and fisheries – Lehodey et al. (2012)

Antarctic temperature changes during the last millennium: evaluation of simulations and reconstructions – Goosse et al. (2012)

The unusual persistence of an ozone hole over a southern mid-latitude station during the Antarctic spring 2009: a multi-instrument study – Wolfram et al. (2012) [FULL TEXT]

Glacier changes from 1966–2009 in the Gongga Mountains, on the south-eastern margin of the Qinghai-Tibetan Plateau and their climatic forcing – Pan et al. (2012) [FULL TEXT]

Aviation-induced radiative forcing and surface temperature change in dependency of the emission altitude – Frömming et al. (2012)

Assessing the value of Microwave Sounding Unit–radiosonde comparisons in ascertaining errors in climate data records of tropospheric temperatures – Mears et al. (2012)

The Swiss Alpine glaciers’ response to the global ’2 °C air temperature target’ – Salzmann et al. (2012) [FULL TEXT]


CLASSIC OF THE WEEK: Atkins (1938)

Daylight in Relation to Climate and Health – Atkins (1938) [FULL TEXT]

Abstract: No abstract. Deals with solar radiation basics.

Citation: Atkins, W. R. G., The British Medical Journal, 1938, 2, 565.


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 3 Comments »

New research from last week 39/2012

Posted by Ari Jokimäki on October 1, 2012

Studies from Africa have so far been rather rare in these weekly batches but this week we have two papers from Nigeria. They are about farmers and forests. We also have studies on Atlantic Warm Pool corals, atmospheric carbon dioxide, coal burning, coastal heat waves, climate effect of cosmic rays, Swiss forests, NAO state, and of course we have our weekly Arctic sea ice paper. Well, ok, in the other paper section we also have couple of Arctic sea ice papers. Permafrost also gets treated with couple of papers there. And… well, for the rest, see them yourself.


Positive and negative climatic effects from afforestation in Nigeria

Potential impacts of afforestation on climate change and extreme events in Nigeria – Abiodun et al. (2012)

Abstract: “Afforestation is usually thought as a good approach to mitigate impacts of warming over a region. This study presents an argument that afforestation may have bigger impacts than originally thought by previous studies. The study investigates the impacts of afforestation on future climate and extreme events in Nigeria, using a regional climate model (RegCM3), forced with global climate model simulations. The impacts of seven afforestation options on the near future (2031–2050, under A1B scenario) climate and the extreme events are investigated. RegCM3 replicates essential features in the present-day (1981–2000) climate and the associated extreme events, and adequately simulates the seasonal variations over the ecological zones in the country. However, the model simulates the seasonal climate better over the northern ecological zones than over the southern ecological zones. The simulated spatial distribution of the extreme events agrees well with the observation, though the magnitude of the simulated events is smaller than the observed. The study shows that afforestation in Nigeria could have both positive and negative future impacts on the climate change and extreme events in the country. While afforestation reduces the projected global warming and enhances rainfall over the afforested area (and over coastal zones), it enhances the warming and reduces the rainfall over the north-eastern part of the country. In addition, the afforestation induces more frequent occurrence of extreme rainfall events (flooding) over the coastal region and more frequent occurrence of heat waves and droughts over the semi-arid region. The positive and negative impacts of the afforestation are not limited to Nigeria; they extend to the neighboring countries. While afforestation lowers the warming and enhances rainfall over Benin Republic, it increases the warming and lowers the rainfall over Niger, Chad and Cameroon. The result of the study has important implication for the ongoing climate change mitigation and adaptation efforts in Nigeria.”

Citation: Babatunde J. Abiodun, Ayobami T. Salami, Olaniran J. Matthew and Sola Odedokun, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1523-9.


Atlantic Warm Pool corals as recorders of sea surface temperature

Corals record persistent multidecadal SST variability in the Atlantic Warm Pool since 1775AD – Vásquez-Bedoya et al. (2012)

Abstract: “Accurate low-latitude sea surface temperature (SST) records that predate the instrumental era are needed to put recent warming in the context of natural climate variability, and to evaluate the persistence of lower frequency climate variability prior to the instrumental era and the possible influence of anthropogenic climate change on this variability. Here we present a 235-year long SST reconstruction based on annual growth rates (linear extension) of three colonies of the Atlantic coral Siderastrea siderea sampled at two sites on the northeastern Yucatan Peninsula, Mexico, located within the Atlantic Warm Pool (AWP). AWP SSTs vary in concert the Atlantic Multidecadal Oscillation (AMO), a basin-wide, quasi-periodic (~60-80 years) oscillation of North Atlantic SSTs. We demonstrate that the annual linear growth rates of all three coral colonies are significantly inversely correlated with SST. We calibrate annual linear growth rates to SST between 1900 and 1960 AD. The linear correlation coefficient over the calibration period is r = -0.77, and -0.66 over the instrumental record (1860-2008 AD). We apply our calibration to annual linear growth rates to extend the SST record to 1775AD and show that multi-decadal SST variability has been a persistent feature of the AWP, and likely, of the North Atlantic over this time period. Our results imply that tropical Atlantic SSTs remained within 1 {degree sign}C of modern values during the past 225 years, consistent with a previous reconstruction based on coral growth rates and with most estimates based on the Mg/Ca of planktonic foraminifera from marine sediments.”

Citation: Vásquez-Bedoya, L. F., A. L. Cohen, D. W. Oppo, and P. Blanchon (2012), Corals record persistent multidecadal SST variability in the Atlantic Warm Pool since 1775AD, Paleoceanography, doi:10.1029/2012PA002313.


Abrupt change in atmospheric carbon dioxide during the last ice age

Abrupt change in atmospheric CO2 during the last ice age – Ahn et al. (2012)

Abstract: “During the last glacial period atmospheric carbon dioxide and temperature in Antarctica varied in a similar fashion on millennial time scales, but previous work indicates that these changes were gradual. In a detailed analysis of one event we now find that approximately half of the CO2 increase that occurred during the 1500-year cold period between Dansgaard-Oeschger (DO) events 8 and 9 happened rapidly, over less than two centuries. This rise in CO2 was synchronous with, or slightly later than, a rapid increase of Antarctic temperature inferred from stable isotopes.”

Citation: Ahn, J., E. Brook, A. Schmittner, and K. J. Kreutz (2012), Abrupt change in atmospheric CO2 during the last ice age, Geophys. Res. Lett., doi:10.1029/2012GL053018.


Reduction of coal burning might lead to rapid near-term warming due to decrease in aerosol cooling

Aerosol contribution to the rapid warming of near-term climate under RCP 2.6 – Chalmers et al. (2012) [FULL TEXT]

Abstract: “The importance of aerosol emissions for near term climate projections is investigated by analysing simulations with the HadGEM2-ES model under two different emissions scenarios: RCP2.6 and RCP4.5. It is shown that the near term warming projected under RCP2.6 is greater than under RCP4.5, even though the greenhouse gas forcing is lower. Rapid and substantial reductions in sulphate aerosol emissions due to a reduction of coal burning in RCP2.6 lead to a reduction in the negative shortwave forcing due to aerosol direct and indirect effects. Indirect effects play an important role over the northern hemisphere oceans, especially the subtropical northeastern Pacific where an anomaly of 5-10\,Wm$^{-2}$ develops. The pattern of surface temperature change is consistent with the expected response to this surface radiation anomaly, whilst also exhibiting features that reflect redistribution of energy, and feedbacks, within the climate system. These results demonstrate the importance of aerosol emissions as a key source of uncertainty in near term projections of global and regional climate.”

Citation: Chalmers, N., E. J. Highwood, E. Hawkins, R. T. Sutton, and L. J. Wilcox (2012), Aerosol contribution to the rapid warming of near-term climate under RCP 2.6, Geophys. Res. Lett., doi:10.1029/2012GL052848.


Coastal heat waves are projected to intensify relative to background warming in California

California heat waves in the present and future – Gershunov & Guirguis (2012)

Abstract: “Current and projected heat waves are examined over California and its sub-regions in observations and downscaled global climate model (GCM) simulations. California heat wave activity falls into two distinct types: (1) typically dry daytime heat waves and (2) humid nighttime-accentuated events (Type I and Type II, respectively). The four GCMs considered project Type II heat waves to intensify more with climate change than the historically characteristic Type I events, although both types are projected to increase. This trend is already clearly observed and simulated to various degrees over all sub-regions of California. Part of the intensification in heat wave activity is due directly to mean warming. However, when one considers non-stationarity in daily temperature variance, desert heat waves are expected to become progressively and relatively less intense while coastal heat waves are projected to intensify even relative to the background warming. This result generally holds for both types of heat waves across models. Given the high coastal population density and low acclimatization to heat, especially humid heat, this trend bodes ill for coastal communities, jeopardizing public health and stressing energy resources.”

Citation: Gershunov, A. and K. Guirguis (2012), California heat waves in the present and future, Geophys. Res. Lett., doi:10.1029/2012GL052979.


Melt ponds on Arctic sea ice are important to include to model simulations

Impact of melt ponds on Arctic sea ice simulations from 1990 to 2007 – Flocco et al. (2012)

Abstract: “The extent and thickness of the Arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in September 2007 and 2011 and climate models did not predict this decline. One of the processes poorly represented in sea ice models is the formation and evolution of melt ponds. Melt ponds form on Arctic sea ice during the melting season and their presence affects the heat and mass balances of the ice cover, mainly by decreasing the value of the surface albedo by up to 20%. We have developed a melt pond model suitable for forecasting the presence of melt ponds based on sea ice conditions. This model has been incorporated into the Los Alamos CICE sea ice model, the sea ice component of several IPCC climate models. Simulations for the period 1990 to 2007 are in good agreement with observed ice concentration. In comparison to simulations without ponds, the September ice volume is nearly 40 % lower. Sensitivity studies within the range of uncertainty reveal that, of the parameters pertinent to the present melt pond parameterization and for our prescribed atmospheric and oceanic forcing, variations of optical properties and the amount of snowfall have the strongest impact on sea ice extent and volume. We conclude that melt ponds will play an increasingly important role in the melting of the Arctic ice cover and their incorporation in the sea ice component of Global Circulation Models is essential for accurate future sea ice forecasts.”

Citation: Flocco, D., D. Schroeder, D. L. Feltham, and E. C. Hunke (2012), Impact of melt ponds on Arctic sea ice simulations from 1990 to 2007, J. Geophys. Res., doi:10.1029/2012JC008195.


Also diurnal temperature range angle of cosmic rays is irrelevant for climate, try again

Examining a solar-climate link in diurnal temperature ranges – Laken et al. (2012) [FULL TEXT]

Abstract: “A recent study has suggested a link between the surface level diurnal temperature range (DTR) and variations in the cosmic ray (CR) flux. As the DTR is an effective proxy for cloud cover, this result supports the notion that widespread cloud changes may be induced by the CR flux. If confirmed, this would have significant implications for our understanding of natural climate forcings. Here, we perform a detailed investigation of the relationships between DTR and solar activity (total solar irradiance and the CR flux) from more than 60 years of NCEP/NCAR reanalysis data and observations from meteorological station data. We find no statistically significant evidence to suggest that the DTR is connected to either long-term solar periodicities (11 or 1.68-year) or short-term (daily timescale) fluctuations in solar activity, and we attribute previous reports on the contrary to an incorrect estimation of the statistical significance of the data. If a CR–DTR relationship exists, based on the estimated noise in DTR composites during Forbush decrease (FD) events, the DTR response would need to be larger than 0.03°C per 1% increase in the CR flux to be reliably detected. Compared with a much smaller rough estimate of −0.005°C per 1% increase in the CR flux expected if previous claims that FD events cause reductions in the cloud cover are valid, we conclude it is not possible to detect a solar related responses in station-based or reanalysis-based DTR data sets related to a hypothesized CR–cloud link, as potential signals would be drowned in noise.”

Citation: Laken, B., J. Čalogović, T. Shahbaz, and E. Pallé (2012), Examining a solar-climate link in diurnal temperature ranges, J. Geophys. Res., 117, D18112, doi:10.1029/2012JD017683.


Scots pine forest is turning into oak forest in Swiss Rhone valley

Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests – Rigling et al. (2012)

Abstract: “An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low-elevation forests is changing: The sub-boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub-Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analyzed data from the Swiss National Forest Inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, while oak regeneration was comparably abundant. While both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occuring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services.”

Citation: A. Rigling, C. Bigler, B. Eilmann, E. Feldmeyer-Christe, U. Gimmi, C. Ginzler, U. Graf, P. Mayer, G. Vacchiano, P. Weber, T. Wohlgemuth, R. Zweifel, M. Dobbertin, Global Change Biology, DOI: 10.1111/gcb.12038.


NAO state generally coincides with Northern Hemisphere climate but during MWP there were no notable changes in NAO

Variability of the North Atlantic Oscillation over the past 5,200 years – Olsen et al. (2012)

Abstract: “Climate in the Arctic region and northwestern Europe is strongly affected by the North Atlantic Oscillation (NAO), the dominant mode of atmospheric variability at mid-latitudes in the North Atlantic region. The NAO index is an indicator of atmospheric circulation and weather patterns: when the index is positive, Europe and the eastern US are mild and wet, whereas Greenland and northern Canada are cold and dry. A negative index is associated with the reverse pattern. Reconstructions of the NAO have so far been limited to the past 900 years3. Here we analyse a 5,200-year-long, high-resolution lake sediment record from southwestern Greenland to reconstruct lake hypolimnic anoxia, and link the results to an existing reconstruction of the NAO index from tree rings and speleothems3. Using the relationship between the two records, we find that around 4,500 and 650 years ago—around the end of the Holocene Thermal Maximum and the beginning of the Little Ice Age, respectively—the NAO changed from generally positive to variable, intermittently negative conditions. We suggest that variability in the dominant state of the NAO tend to coincide with large-scale changes in Northern Hemisphere climate. However, the onset of the Medieval Climate Anomaly was not associated with any notable changes in the NAO.”

Citation: Jesper Olsen, N. John Anderson, & Mads F. Knudsen, Nature Geoscience(2012), doi:10.1038/ngeo1589.


Nigerian farmers have noticed changes in climate and adjusted their farming practices to adapt

Smallholder farmers’ perceptions of and adaptations to climate change in the Nigerian savanna – Tambo & Abdoulaye (2012)

Abstract: “The savanna region of Africa is a potential breadbasket of the continent but is severely affected by climate change. Understanding farmers’ perceptions of climate change and the types of adjustments they have made in their farming practices in response to these changes will offer some insights into necessary interventions to ensure a successful adaptation in the region. This paper explores how smallholder farmers in the Nigerian savanna perceive and adapt to climate change. It is based on a field survey carried out among 200 smallholder farm households selected from two agro-ecological zones. The results show that most of the farmers have noticed changes in climate and have consequently adjusted their farming practices to adapt. There are no large differences in the adaptation practices across the region, but farmers in Sudan savanna agro-ecological zone are more likely to adapt to changes in temperature than those in northern Guinea savanna. The main adaptation methods include varying planting dates, use of drought tolerant and early maturing varieties and tree planting. Some of the farmers are facing limitations in adapting because of lack of information on climate change and the suitable adaptation measures and lack of credit. The study then concludes that to ensure successful adaptation to climate change in the region, concerted efforts are needed to design and promote planned adaptation measures that fit into the local context and also to educate farmers on climate change and appropriate adaptation measures.”

Citation: Justice Akpene Tambo and Tahirou Abdoulaye, Regional Environmental Change, 2012, DOI: 10.1007/s10113-012-0351-0.


Other papers from last week

Did the Arctic ice recover? Demographics of true and false climate facts – Hamilton (2012)

Visibility trends in Tehran during 1958–2008 – Sabetghadam et al. (2012)

Soil carbon in the Arctic and the permafrost carbon feedback – van Huissteden & Dolman (2012)

Uncertainties in the global temperature change caused by carbon release from permafrost thawing – Burke et al. (2012) [FULL TEXT]

An integrated flask sample collection system for greenhouse gas measurements – Turnbull et al. (2012) [FULL TEXT]

Decadal changes in surface air temperature variability and cold surge characteristics over Northeast Asia and their relation with the Arctic Oscillation for the past three decades (1979-2011) – Woo et al. (2012)

A re-examination of evidence for the North Atlantic “1500-year cycle” at Site 609 – Obrochta et al. (2012)

Decadal variations in estimated surface solar radiation over Switzerland since the late 19th century – Sanchez-Lorenzo & Wild (2012)

Evaluating global trends (1988–2010) in harmonized multi-satellite surface soil moisture – Dorigo et al. (2012)

Ocean heat uptake and its consequences for the magnitude of sea level rise and climate change – Kuhlbrodt & Gregory (2012)

A sea ice free summer Arctic within 30 years: An update from CMIP5 models – Wang & Overland (2012)

Can we predict the duration of an interglacial? – Txedakis et al. (2012) [FULL TEXT]

Past millennial solar forcing magnitude – A statistical hemispheric-scale climate model versus proxy data comparison – Hind & Moberg (2012) [FULL TEXT]

Potential impacts of northeastern Eurasian snow cover on generation of dust storms in northwestern China during spring – Lee et al. (2012)

Climate-diameter growth relationships of black spruce and jack pine trees in boreal Ontario, Canada – Subedi & Sharma (2012)

Methane Emissions from rice paddies, natural wetlands, and lakes in China: Synthesis and New Estimate – Chen et al. (2012)


CLASSIC OF THE WEEK: Malmfors (1949)

Recordinds of Cosmic Radiation – Malmfors (2012) [FULL TEXT]

Abstract: “The main purpose of the registrations reported here has been to study the diurnal variations of C. R. and especially to investigate how the amplitude and the phase of the variation depend on the direction of incidence. Since statistical fluctuations will dominate over the significant ones unless a sufficiently large number of coincidences is counted, it has been necessary to use an apparatus with a high counting speed. C. R. has been recorded continuously in Stockholm (magn. lat. 58°) since 1. 10. 1947 by means of large counters in coincidence circuit. Recordings have been made in three different directions simultaneously, and the total number of particles counted amounts to 109. The material has been analyzed with respect to diurnal variation. This analysis definitely proves that the variation is not the same in different directions. A term called C. R. activity has been introduced for the purpose of classifying the registrations according to the magnitude of the variation for each day. An analysis shows that large activity is very often observed during consecutive days.”

Citation: K. G. Malmfors, Tellus, Volume 1, Issue 2, pages 55–61, May 1949, DOI: 10.1111/j.2153-3490.1949.tb01259.x.


When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Posted in Climate science | 1 Comment »

 
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