Q: Are Parisian air-conditioners making things all nice and cool or warming up the place? A: Warming up the place. Q: What is it that was travestically missing but has been found now? A: Energy. Q: What is the hypothesis that is constantly debunked by numerous peer-reviewed studies and gets yet another blow this week? A: Cosmic ray-climate connection. Q: As just about anything seems to affect North-Atlantic/Europe weather, does Indian summer monsoon do it too? A: Yes. Q: What is slowly increasing tropical Pacific east-west temperature gradient? A: Global warming. Q: What Alaskan treeline trees do when climate warms? A: Anything they feel like doing. Q: What lives longer if days get warmer but doesn’t if only nights get warmer? A: Root. Q: How do you explain carbon dioxide increase during last glacial termination? A: With salt, of course. Q: What keeps AMOC running? A: Mountains.

We also have studies on orbital control of carbon cycle, positive low-level cloud feedback, different kinds of cloud feedbacks, tropical glaciers, global sea level, electromagnetic imaging of permafrost, 1988 land uptake of carbon, temperature control over tropical tropopause water vapor and clouds, and Canadian lake plankton.

Past climate recording tropical glaciers are melting away

Tropical glaciers, recorders and indicators of climate change, are disappearing globally – Thompson et al. (2012) [FULL TEXT]

Abstract: “In this paper we review the interaction of El Niño Southern Oscillation (ENSO) variability and warming trends recorded in ice-core records from high-altitude tropical glaciers, discuss the implications of the warming trends for the glaciers and consider the societal implications of glacier retreat. ENSO has strong impacts on meteorological phenomena that directly or indirectly affect most regions on the planet and their populations. Many tropical ice fields have provided continuous annually resolved proxy records of climatic and environmental variability preserved in measurable parameters, especially oxygen and hydrogen isotopic ratios (δ¹⁸O, δD) and the net mass balance (accumulation). These records present an opportunity to examine the nature of tropical climate variability in greater detail and to extract new information on linkages between rising temperatures on tropical glaciers and equatorial Pacific sea surface temperatures in critical ENSO indicator regions. The long-term climate records from a collection of high-altitude tropical ice cores provide the longer-term context essential for assessing the significance of the magnitude and rate of current climate changes that are in large measure driving glacier retreat. The well-documented ice loss on Quelccaya in the Peruvian Andes, Naimona’nyi in the Himalaya, Kilimanjaro in eastern Africa and the ice fields near Puncak Jaya in Papua, Indonesia, presents a grim future for low-latitude glaciers. The ongoing melting of these ice fields (response) is consistent with model predictions for a vertical amplification of temperature in the tropics (driver) and has serious implications for the people who live in these areas.”

Citation: Thompson, Lonnie G.; Mosley-Thompson, Ellen; Davis, Mary E.; Brecher, Henry H., Annals of Glaciology, Volume 52, Number 59, December 2011 , pp. 23-34(12).

Global sea level budget since 1850

The historical global sea-level budget – Moore et al. (2012) [FULL TEXT]

Abstract: “We analyze the global sea-level budget since 1850. Good estimates of sea-level contributions from glaciers and small ice caps, the Greenland ice sheet and thermosteric sea level are available over this period, though considerable scope for controversy remains in all. Attempting to close the sea-level budget by adding the components results in a residual displaying a likely significant trend of 0.37 mm a^-1 from 1955 to 2005, which can, however, be reasonably closed using estimated melting from unsurveyed high-latitude small glaciers and ice caps. The sea-level budget from 1850 is estimated using modeled thermosteric sea level and inferences from a small number of mountain glaciers. This longer-term budget has a residual component that displays a rising trend likely associated with the end of the Little Ice Age, with much decadal-scale variability that is probably associated with variability in the global water cycle, ENSO and long-term volcanic impacts.”

Citation: Moore, J.C.; Jevrejeva, S.; Grinsted, A., Annals of Glaciology, Volume 52, Number 59, December 2011 , pp. 8-14(7).

Explaining carbon dioxide increase during last glacial termination

Impact of oceanic processes on the carbon cycle during the last termination – Bouttes et al. (2012) [FULL TEXT]

Abstract: “During the last termination (from ~18 000 years ago to ~9000 years ago), the climate significantly warmed and the ice sheets melted. Simultaneously, atmospheric CO₂ increased from ~190 ppm to ~260 ppm. Although this CO₂ rise plays an important role in the deglacial warming, the reasons for its evolution are difficult to explain. Only box models have been used to run transient simulations of this carbon cycle transition, but by forcing the model with data constrained scenarios of the evolution of temperature, sea level, sea ice, NADW formation, Southern Ocean vertical mixing and biological carbon pump. More complex models (including GCMs) have investigated some of these mechanisms but they have only been used to try and explain LGM versus present day steady-state climates. In this study we use a coupled climate-carbon model of intermediate complexity to explore the role of three oceanic processes in transient simulations: the sinking of brines, stratification-dependent diffusion and iron fertilization. Carbonate compensation is accounted for in these simulations. We show that neither iron fertilization nor the sinking of brines alone can account for the evolution of CO₂, and that only the combination of the sinking of brines and interactive diffusion can simultaneously simulate the increase in deep Southern Ocean δ¹³C. The scenario that agrees best with the data takes into account all mechanisms and favours a rapid cessation of the sinking of brines around 18 000 years ago, when the Antarctic ice sheet extent was at its maximum. In this scenario, we make the hypothesis that sea ice formation was then shifted to the open ocean where the salty water is quickly mixed with fresher water, which prevents deep sinking of salty water and therefore breaks down the deep stratification and releases carbon from the abyss. Based on this scenario, it is possible to simulate both the amplitude and timing of the long-term CO₂increase during the last termination in agreement with ice core data. The atmospheric δ¹³C appears to be highly sensitive to changes in the terrestrial biosphere, underlining the need to better constrain the vegetation evolution during the termination.”

Citation: Bouttes, N., Paillard, D., Roche, D. M., Waelbroeck, C., Kageyama, M., Lourantou, A., Michel, E., and Bopp, L.: Impact of oceanic processes on the carbon cycle during the last termination, Clim. Past, 8, 149-170, doi:10.5194/cp-8-149-2012, 2012.

Possible link between orbital forcing and carbon cycle also under mid-Cretaceous greenhouse conditions

Orbital control on carbon cycle and oceanography in the mid-Cretaceous greenhouse – Giorgioni et al. (2012)

Abstract: “We established a new high-resolution carbonate carbon isotope record of the Albian interval of the Marne a Fucoidi Formation (Central Apennines, Italy), which was deposited on the southern margin of the western Tethys Ocean. Bulk carbonate sampled with 10–15 cm spacing was used for the construction of a continuous carbon isotope curve through the Albian stage. Spectral analyses reveal prominent 400 kyr cyclicity in the δ13C curve, which correlates with Milankovitch long eccentricity changes. Cycles occurring in our record resemble those observed in several Cenozoic δ13C records, suggesting that a link between orbital forcing and carbon cycling existed also under mid-Cretaceous greenhouse conditions. Based on comparisons with Cenozoic eccentricity-carbon cycle links we hypothesize that 400 kyr cycles in the mid-Cretaceous were related to a fluctuating monsoonal regime, coupled with an unstable oceanic structure, which made the oceanic carbon reservoir sensitive to orbital variations. In the Tethys these oceanographic conditions lasted until the Late Albian, and then were replaced by a more stable circulation mode, less sensitive to orbital forcing.”

Citation: Giorgioni, M., H. Weissert, S. M. Bernasconi, P. A. Hochuli, R. Coccioni, and C. E. Keller (2012), Orbital control on carbon cycle and oceanography in the mid-Cretaceous greenhouse, Paleoceanography, 27, PA1204, doi:10.1029/2011PA002163.

Mountain ranges have strong role in maintaining Atlantic Meridional Overturning Circulation

Mountain ranges favour vigorous Atlantic meridional overturning – Sinha et al. (2012)

Abstract: “We use a global Ocean-Atmosphere General Circulation Model (OAGCM) to show that the major mountain ranges of the world have a significant role in maintenance of the Atlantic Meridional Overturning Circulation (AMOC). A simulation with mountains has a maximum AMOC of 18 Sv (1 Sv = 10⁶ m³ s^-1) compared with ∼0 Sv for a simulation without mountains. Atlantic heat transport at 25°N is 1.1 PW with mountains compared to 0.2 PW without. The difference in AMOC is due to major changes in surface heat and freshwater (FW) fluxes over the Atlantic. In the Pacific changed surface fluxes lead to a meridional overturning circulation of 10 Sv. Our results suggest that the effects of mountains on the large-scale atmospheric circulation is to force the ocean towards a state with a vigorous AMOC and with no overturning in the Pacific.”

Citation: Sinha, B., A. T. Blaker, J. J.-M. Hirschi, S. Bonham, M. Brand, S. Josey, R. S. Smith, and J. Marotzke (2012), Mountain ranges favour vigorous Atlantic meridional overturning, Geophys. Res. Lett., 39, L02705, doi:10.1029/2011GL050485.

Why is there positive feedback from low level clouds in climate models?

Interpretation of the positive low-cloud feedback predicted by a climate model under global warming – Brient & Bony (2012) [FULL TEXT]

Abstract: “The response of low-level clouds to climate change has been identified as a major contributor to the uncertainty in climate sensitivity estimates among climate models. By analyzing the behaviour of low-level clouds in a hierarchy of models (coupled ocean-atmosphere model, atmospheric general circulation model, aqua-planet model, single-column model) using the same physical parameterizations, this study proposes an interpretation of the strong positive low-cloud feedback predicted by the IPSL-CM5A climate model under climate change. In a warmer climate, the model predicts an enhanced clear-sky radiative cooling, stronger surface turbulent fluxes, a deepening and a drying of the planetary boundary layer, and a decrease of tropical low-clouds in regimes of weak subsidence. We show that the decrease of low-level clouds critically depends on the change in the vertical advection of moist static energy from the free troposphere to the boundary-layer. This change is dominated by variations in the vertical gradient of moist static energy between the surface and the free troposphere just above the boundary-layer. In a warmer climate, the thermodynamical relationship of Clausius-Clapeyron increases this vertical gradient, and then the import by large-scale subsidence of low moist static energy and dry air into the boundary layer. This results in a decrease of the low-level cloudiness and in a weakening of the radiative cooling of the boundary layer by low-level clouds. The energetic framework proposed in this study might help to interpret inter-model differences in low-cloud feedbacks under climate change.”

Citation: Florent Brient and Sandrine Bony, Climate Dynamics, DOI: 10.1007/s00382-011-1279-7.

No link between cosmic rays/sun and MODIS cloud anomalies

A decade of the Moderate Resolution Imaging Spectroradiometer: is a solar – cloud link detectable? – Laken et al. (2012)

Abstract: “Based on the results of decadal correlation studies between International Satellite Cloud Climatology Project detected cloud anomalies and the galactic cosmic ray (GCR) flux it has been suggested that a relationship exists between solar activity and cloud cover. If valid, such a relationship could have important implications for our understanding of recent climate change. In this work, we present an analysis of the first decade of MODerate Resolution Imaging Spectroradiometer (MODIS) detected cloud anomalies, and compare the data at global and local geographical resolutions to Total Solar Irradiance (TSI), GCR variations and the Multivariate El Niño Southern Oscillation Index. We identify no statistically significant correlations between cloud anomalies and TSI/GCR variations, and conclude that solar related variability is not a primary driver of monthly to annual MODIS cloud variability. We observe a net increase in cloud detected by MODIS over the past decade of ~0.58 %, arising from a combination of a reduction in high – middle level cloud (−0.31 %) and an increase in low level cloud (of 0.89%); these long term changes may be largely attributed to ENSO induced cloud variability.”

Citation: Benjamin Laken, Enric Pallé, and Hiroko Miyahara, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00306.1.

Electromagnetic imaging of permafrost down to 100m depths

Airborne electromagnetic imaging of discontinuous permafrost – Minsley et al. (2012)

Abstract: “The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to streamflow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ∼1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ∼4 million years and the configuration of permafrost to depths of ∼100 meters in the Yukon Flats area near Fort Yukon, Alaska. The Yukon Flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south, making it an important location for examining permafrost dynamics. Our results not only provide a detailed snapshot of the present-day configuration of permafrost, but they also expose previously unseen details about potential surface – groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past ∼1,000 years. This work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic, climatic, and ecological processes, and has significant implications for the stewardship of Arctic environments.”

Citation: Minsley, B. J., et al. (2012), Airborne electromagnetic imaging of discontinuous permafrost, Geophys. Res. Lett., 39, L02503, doi:10.1029/2011GL050079.

New analysis of different kinds of cloud feedbacks

Computing and Partitioning Cloud Feedbacks using Cloud Property Histograms. Part I: Cloud Radiative Kernels – Zelinka et al. (2012) [FULL TEXT, PRESENTATION MATERIAL]

Abstract: “We propose a novel technique for computing cloud feedbacks using histograms of cloud fraction as a joint function of cloud top pressure (CTP) and optical depth (τ). These histograms were generated by the International Satellite Cloud Climatology Project (ISCCP) simulator that was incorporated into doubled CO2 simulations from eleven global climate models in the Cloud Feedback Model Intercomparison Project. We use a radiative transfer model to compute top of atmosphere flux sensitivities to cloud fraction perturbations in each bin of the histogram for each month and latitude. Multiplying these cloud radiative kernels with histograms of modeled cloud fraction changes at each grid point per unit of global warming produces an estimate of cloud feedback. Spatial structures and globally integrated cloud feedbacks computed in this manner agree remarkably well with the adjusted change in cloud radiative forcing. The global and annual mean model-simulated cloud feedback is dominated by contributions from medium thickness (3.6 ≤ τ < 23) cloud changes, but thick (τ ≥ 23) cloud changes cause the rapid transition of cloud feedback values from positive in midlatitudes to negative poleward of 50°S and 70°N. High (CTP < 440 hPa) cloud changes are the dominant contributor to LW cloud feedback, but because their LW and SW impacts are in opposition, they contribute less to the net cloud feedback than do the positive contributions from low (CTP ≥ 680 hPa) cloud changes. Mid-level (440 ≤ CTP < 680 hPa) cloud changes cause positive SW cloud feedbacks that are 80% as large as those due to low clouds. Finally, high cloud changes induce wider ranges of LW and SW cloud feedbacks across models than do low clouds.”

Part 2 of this paper was published earlier.

Citation: Mark D. Zelinka, Stephen A. Klein, Dennis L. Hartmann, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00248.1.

Missing energy was not missing after all

Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty – Loeb et al. (2012)

Abstract: “Global climate change results from a small yet persistent imbalance between the amount of sunlight absorbed by Earth and the thermal radiation emitted back to space. An apparent inconsistency has been diagnosed between interannual variations in the net radiation imbalance inferred from satellite measurements and upper-ocean heating rate from in situ measurements, and this inconsistency has been interpreted as ‘missing energy’ in the system. Here we present a revised analysis of net radiation at the top of the atmosphere from satellite data, and we estimate ocean heat content, based on three independent sources. We find that the difference between the heat balance at the top of the atmosphere and upper-ocean heat content change is not statistically significant when accounting for observational uncertainties in ocean measurements, given transitions in instrumentation and sampling. Furthermore, variability in Earth’s energy imbalance relating to El Niño-Southern Oscillation is found to be consistent within observational uncertainties among the satellite measurements, a reanalysis model simulation and one of the ocean heat content records. We combine satellite data with ocean measurements to depths of 1,800 m, and show that between January 2001 and December 2010, Earth has been steadily accumulating energy at a rate of 0.50±0.43 Wm−2 (uncertainties at the 90% confidence level). We conclude that energy storage is continuing to increase in the sub-surface ocean.”

Citation: Norman G. Loeb, John M. Lyman, Gregory C. Johnson, Richard P. Allan, David R. Doelling, Takmeng Wong, Brian J. Soden & Graeme L. Stephens, Nature Geoscience. doi:10.1038/ngeo1375.

Day warming increases root lifespan, night warming doesn’t

Day and night warming have different effect on root lifespan – Bai et al. (2012) [FULL TEXT]

Abstract: “Roots are key components of C cycling in terrestrial ecosystems and play an important role in the regulation of response of terrestrial ecosystems to global climate warming, which is predicted to occur with greater warming magnitudes at night than during daytime across different regions on the Earth. However, there has been no detailed study to investigate the effect of asymmetrical warming on root dynamics at the level of terrestrial ecosystems. To understand the effects of day and night warming on root lifespan in the semiarid temperate steppe in northern China, a field study with a full factorial design including control, day warming, night warming and continuous warming was conducted using modified rhizotron technique during three growing seasons in 2007–2009. Our results show that day, night and continuous warming had different effects on longevity of roots born in spring, summer and autumn, and that day warming significantly prolonged overall lifespan for the roots born in the three growing seasons, while night warning had no effect on overall lifespan. Day and night warming had different effects on root non-structural carbohydrate content, suggesting that allocation of photoassimilate may account for the differential responses of root lifespan to day and night warming. These results differ from other processes associated with ecosystems C cycle such as total ecosystem productivity, net ecosystem productivity and soil respiration. Our findings highlight that it is essential to incorporate the differential effects of day and night warming on root dynamics into simulating and predicting the responses and feedbacks of terrestrial ecosystems C cycling to global warming.”

Citation: Bai, W. M., Xia, J. Y., Wan, S. Q., Zhang, W. H., and Li, L. H.: Day and night warming have different effect on root lifespan, Biogeosciences, 9, 375-384, doi:10.5194/bg-9-375-2012, 2012.

Abrupt increase in the land uptake of carbon in 1988

Identification and characterization of abrupt changes in the land uptake of carbon – Beaulieu et al. (2012)

Abstract: “A recent study of the net land carbon sink estimated using the Mauna Loa, Hawaii atmospheric CO₂ record, fossil fuel estimates, and a suite of ocean models suggests that the mean of the net land carbon uptake remained approximately constant for three decades and increased after 1988/1989. Due to the large variability in the net land uptake, it is not possible to determine the exact timing and nature of the increase robustly by visual inspection. Here, we develop a general methodology to objectively determine the nature and timing of the shift in the net land uptake based on the Schwarz Information Criterion. We confirm that it is likely that an abrupt shift in the mean net land carbon uptake occurred in 1988. After taking into account the variability in the net land uptake due to the influence of volcanic aerosols and the El Niño Southern Oscillation, we find that it is most likely that there is a remaining step increase at the same time (p-values of 0.01 and 0.04 for Mauna Loa and South Pole, respectively) of about 1 Pg C/yr. Thus, we conclude that neither the effect of volcanic eruptions nor the El Niño Southern Oscillation are the causes of the sudden increase of the land carbon sink. By also applying our methodology to the atmospheric growth rate of CO₂, we demonstrate that it is likely that the atmospheric growth rate of CO₂ exhibits a step decrease between two fitted lines in 1988–1989, which is most likely due to the shift in the net land uptake of carbon.”

Citation: Beaulieu, C., J. L. Sarmiento, S. E. Mikaloff Fletcher, J. Chen, and D. Medvigy (2012), Identification and characterization of abrupt changes in the land uptake of carbon, Global Biogeochem. Cycles, 26, GB1007, doi:10.1029/2010GB004024.

Complex response of Alaskan trees to warming

Do limiting factors at Alaskan treelines shift with climatic regimes? – Ohse et al. (2012) [FULL TEXT]

Abstract: “Trees at Alaskan treelines are assumed to be limited by temperature and to expand upslope and/or to higher latitudes with global warming. However, recent studies describe negative temperature responses and drought stress of Alaskan treeline trees in recent decades. In this study, we have analyzed the responses of treeline white spruce to temperature and precipitation according to different climatic regimes in Alaska, described as negative (cool) and positive (warm) phases of the Pacific Decadal Oscillation (PDO). We found that in three consecutive phases (positive from 1925–46, negative from 1947–76, and positive again from 1977–98), the growth responses to temperature and precipitation differed markedly. Before 1947, in a phase of warm winters and with summer temperatures being close to the century mean, the trees at most sites responded positively to summer temperature, as one would expect from treeline trees at northern high latitudes. Between 1947 and 1976, a phase of cold winters and average summers, the trees showed similar responses, but a new pattern of negative responses to the summer temperature of the year prior to growth coupled with positive responses to the precipitation in the same year emerged at some sites. As the precipitation was relatively low at those sites, we assume that drought stress might have played a role. However, the climate responses were not uniform but were modified by regional gradients (trees at northern sites responded more often to temperature than trees at southern sites) and local site conditions (forest trees responded more often to precipitation than treeline trees), possibly reflecting differences in energy and water balance across regions and sites, respectively. However, since the shift in the PDO in 1976 from a negative to a positive phase, the trees’ climate–growth responses are much less pronounced and climate seems to have lost its importance as a limiting factor for the growth of treeline white spruce. If predictions of continued warming and precipitation increase at northern high latitudes hold true, the growth of Alaskan treeline trees will likely depend on the ratio of temperature and precipitation increase more than on their absolute values, as well as on the interaction of periodic regime shifts with the global warming trend. Once a climatic limitation is lifted, other factors, such as insect outbreaks or interspecific competition, might become limiting to tree growth.”

Citation: B Ohse et al 2012 Environ. Res. Lett. 7 015505 doi:10.1088/1748-9326/7/1/015505.

Indian summer monsoon might have an effect to North Atlantic-Europe climate

Indian summer monsoon influence on the climate in the North Atlantic–European region – Lin & Wu (2012)

Abstract: “Previous studies have shown that climate anomalies over the North Atlantic–Europe (NAE) can influence the Indian summer monsoon (ISM) variability. It is, however, still an outstanding question whether the latter has a significant impact on the former. In this study, observational evidences indicate that the interannual variability of ISM is closely linked to the climate anomalies over NAE. A strong ISM is often associated with significant above normal precipitation over most of western Europe. Meanwhile, positive surface air temperature (SAT) anomalies are usually observed over the Mediterranean, accompanied by below normal SAT in Western Europe during a strong ISM summer. The situation is just opposite during a weak ISM summer. A global primitive equation model is utilized to assess the mechanism of the above observed connection.”

Citation: Hai Lin and Zhiwei Wu, Climate Dynamics, DOI: 10.1007/s00382-011-1286-8.

Possible regional detection of global warming in tropical Pacific

Is a global warming signature emerging in the tropical Pacific? – Ashok et al. (2012)

Abstract: “The tropical pacific experienced a hitherto-unseen anomalous basinwide warming from May 2009 through April 2010 with the maximum warming to the east of the dateline, but for a weak anomalous cooling west of 140°E after early boreal fall. Our observed analysis and model experiments isolate the potential teleconnections from TP during the summer of 2009. Further, we show through an empirical orthogonal function analysis of the tropical Pacific SSTA that the anomalous conditions in TP during this period could have manifested as a canonical El Niño, but for a slowly intensifying background west–east gradient. This zonal SST gradient is subject to an increasing trend associated with global warming. A possible implication is that any further increase in global warming may result in more basinwide warm events in place of canonical El Niños, along with the occurrence of more intense La Niñas and El Niño Modokis.”

Citation: Ashok, K., T. P. Sabin, P. Swapna, and R. G. Murtugudde (2012), Is a global warming signature emerging in the tropical Pacific?, Geophys. Res. Lett., 39, L02701, doi:10.1029/2011GL050232.

Quantification of the effect of air-conditioning on Paris temperatures

How much can air conditioning increase air temperatures for a city like Paris, France? – de Munck et al. (2012)

Abstract: “A consequence of urban heat islands in summer is an increase in the use of air conditioning in urbanized areas, which while cooling the insides of buildings, releases waste heat to the atmosphere. A coupled model consisting of a meso-scale meteorological model (MESO-NH) and an urban energy balance model (TEB) has been used to simulate and quantify the potential impacts on street temperature of four air conditioning scenarios at the scale of Paris. The first case consists of simulating the current types of systems in the city and was based on inventories of dry and evaporative cooling towers and free cooling systems with the river Seine. The other three scenarios were chosen to test the impacts of likely trends in air conditioning equipment in the city: one for which all evaporative and free cooling systems were replaced by dry systems, and the other two designed on a future doubling of the overall air conditioning power but with different technologies. The comparison between the scenarios with heat releases in the street and the baseline case without air conditioning showed a systematic increase in the street air temperature, and this increase was greater at nighttime than day time. It is counter-intuitive because the heat releases are higher during the day. This is due to the shallower atmospheric boundary layer during the night. The increase in temperature was 0.5 °C in the situation with current heat releases, 1 °C with current releases converted to only sensible heat, and 2 °C for the future doubling of air conditioning waste heat released to air. These results demonstrated to what extent the use of air conditioning could enhance street air temperatures at the scale of a city like Paris, and the importance of a spatialized approach for a reasoned planning for future deployment of air conditioning in the city.”

Citation: Cécile de Munck, Grégoire Pigeon, Valéry Masson, Francis Meunier, Pierre Bousquet, Brice Tréméac, Michèle Merchat, Pierre Poeuf, Colette Marchadier, International Journal of Climatology, DOI: 10.1002/joc.3415.

Measurements of temperature controlling water and cirrus clouds at tropical tropopause

Correlation among cirrus ice content, water vapor and temperature in the TTL as observed by CALIPSO and Aura/MLS – Flury et al. (2012) [FULL TEXT]

Abstract: “Water vapor in the tropical tropopause layer (TTL) has a local radiative cooling effect. As a source for ice in cirrus clouds, however, it can also indirectly produce infrared heating. Using NASA A-Train satellite measurements of CALIPSO and Aura/MLS we calculated the correlation of water vapor, ice water content and temperature in the TTL. We find that temperature strongly controls water vapor (correlation r=0.94) and cirrus clouds at 100 hPa (r=−0.9). Moreover we observe that the cirrus seasonal cycle is highly (r=−0.9) anticorrelated with the water vapor variation in the TTL, showing higher cloud occurrence during December-January-February. We further investigate the anticorrelation on a regional scale and find that the strong anticorrelation occurs generally in the ITCZ (Intertropical Convergence Zone). The seasonal cycle of the cirrus ice water content is also highly anticorrelated to water vapor (r=−0.91) and our results support the hypothesis that the total water at 100 hPa is roughly constant. Temperature acts as a main regulator for balancing the partition between water vapor and cirrus clouds. Thus, to a large extent, the depleting water vapor in the TTL during DJF is a manifestation of cirrus formation.”

Citation: Flury, T., Wu, D. L., and Read, W. G.: Correlation among cirrus ice content, water vapor and temperature in the TTL as observed by CALIPSO and Aura/MLS, Atmos. Chem. Phys., 12, 683-691, doi:10.5194/acp-12-683-2012, 2012.

Last century lake sediments in Canada show planktonic shift that is unique during Holocene

Using paleolimnology to track Holocene climate fluctuations and aquatic ontogeny in poorly buffered High Arctic lakes – Rouillard et al. (2012)

Abstract: “Fossil diatom assemblages, and spectrally-inferred dissolved organic carbon (DOC) and sedimentary chlorophyll-a (SedChla) were analysed on lake sediment cores from two poorly buffered lakes on Pim Island (High Arctic Canada) to assess their responses to Holocene climate changes and to document lake ontogeny. Following deglaciation, diatom assemblages were dominated by small benthic Fragilaria sensu lato taxa. During the mid-Holocene there was an abrupt shift to more circumneutral and slightly acidophilous taxa dominated by Achnanthes and Navicula taxa. The most recent sediments, we recorded an increase in the planktonic taxon Cyclotella radiosa. This shift of the last century is the most ecologically unique in the Holocene record and is indicative of longer ice-free summers consistent with modern climate warming. Inferred DOC and SedChla track some of the main Holocene climatic trends documented in the region, including the Holocene Thermal Maximum and Neoglacial period; however, changes in lakewater in DOC did not likely drive any of the recorded shifts in diatom assemblages. Compared to nearby well buffered sites, our poorly buffered lakes recorded a more dynamic diatom response to Holocene environmental change. The decreasing trend in diatom inferred pH is likely due to changes in the acid neutralizing capacity (ANC) driven by the release of alkalinizing base cations from the easily weathered glacial deposits in the early Holocene and later by climate-driven pH dynamics and within-lake dissolved inorganic carbon (DIC) dynamics. The diatom community composition in our study lakes is different and undergoes greater changes than in nearby well buffered lakes suggesting that softwater lakes in the high Arctic may respond most sensitively to climate and other environmental stressors.”

Citation: Alexandra Rouillard, Neal Michelutti, Peter Rosén, Marianne S.V. Douglas, John P. Smol, Palaeogeography, Palaeoclimatology, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2012.01.011.

CLASSIC OF THE WEEK: Chamberlin (1906)

On a Possible Reversal of Deep-Sea Circulation and Its Influence on Geologic Climates – Chamberlin (1906) [FULL TEXT AVAILABLE IN ABSTRACT PAGE]

Abstract: No abstract.

Citation: T. C. Chamberlin, The Journal of Geology, Vol. 14, No. 5, Jul. – Aug.

In this week’s papers global warming is cancelled. Couple of studies almost make it look like northern hemisphere hasn’t warmed at all. Antarctic snowmelt hasn’t increased either, and mass loss of Svalbard glaciers is at least slowing down. One study does see a GHG effect but there still might be less warming than usually is projected. On the other hand, only modest warming does some nasty things to tropical insects and arachnids, and even without warming, ocean acidification is going to cost us billions and billions of dollars (I’m glad that Euro is our currency here in Finland).

Looking at other papers this week, I bet you wouldn’t like to swim in Paleozoic tropical oceans. Scientists have done fancy tricks with Greenland ice core to reveal secrets of an old volcanic eruption. Lord Kelvin seems to be still doing science. Deforestation appears at least in some sense to be cool. We also have studies on sea level rise of southern Europe coast, North-Atlantic warming, Holocene abrupt climate changes, oceanic freshwater fluxes, and South Asia warming distribution.

Deforestation induces large increases in cold event frequency and intensity in South-America

Simulated links between deforestation and extreme cold events in South America – Medvigy et al. (2012)

Abstract: “Many modeling studies have indicated that deforestation will increase the average annual temperature in the Amazon. However, few studies have investigated the potential for deforestation to change the frequency and intensity of extreme events. This problem is addressed here using a variable-resolution GCM. The characteristic length scale (CLS) of the model’s grid mesh over South America is 25 km, comparable to that used by limited-area models. For computational efficiency, the CLS increases to 200 km over the rest of the world. It is found that deforestation induces large changes in the frequency of wintertime extreme cold events. Large increases in cold event frequency and intensity occur in the western Amazon and, surprisingly, in parts of southern South America, far from the actual deforested area. One possible mechanism for these remote effects involves changes in the position of the subtropical jet, caused by temperature changes in the Amazon. Increased understanding of these potential changes in extreme events will be important for local agriculture, natural ecosystems, and the human population.”

Citation: David Medvigy, Robert L. Walko, and Roni Avissar, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00259.1.

Oceanic freshwater flux changes tend to amplify rather than suppress the global warming

Can oceanic freshwater flux amplify global warming? – Zhang & Wu (2012)

Abstract: “The roles of freshwater flux (defined as evaporation minus precipitation) changes in global warming are studied using simulations of a climate model in which the freshwater flux changes are suppressed in the presence of a doubling of CO₂ concentration. The model simulations demonstrate that the warm climate leads to an acceleration of global water cycle which causes freshening in the high latitudes and salinification in the subtropics and midlatitudes. It is found that the freshwater flux changes tend to amplify rather than suppress the global warming. Over the global scale, this amplification is largely associated with high latitude freshening in a warm climate, which leads to a shoaling of the mixed layer depth, weakening of vertical mixing and thus a trapping of CO₂-induced warming in the surface ocean. The latitudinal distribution of SST changes due to the effects of freshwater flux changes in a warm climate is complicated, which involves anomalous advection induced by both salinity and wind stress changes. In addition, atmospheric feedbacks associated with global warming also amplify the SST warming.”

Citation: Liping Zhang and Lixin Wu, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00172.1.

Many causes of North Atlantic mid 1990′s rapid warming

Causes of the Rapid Warming of the North Atlantic ocean in the mid 1990s – Robson et al. (2012)

Abstract: “In the mid-1990s the subpolar gyre of the North Atlantic underwent a remarkable rapid warming, with sea surface temperatures increasing by around 1C in just 2 years. This rapid warming followed a prolonged positive phase of the North Atlantic Oscillation (NAO), but also coincided with an unusually negative NAO index in the winter of 1995/96. By comparing ocean analyses and carefully designed model experiments we show that this rapid warming can be understood as a delayed response to the prolonged positive phase of the NAO, and not simply an instantaneous response to the negative NAO index of 1995/96. Furthermore, we infer that the warming was partly caused by a surge, and subsequent decline, in the Meridional Overturning Circulation and northward heat transport of the Atlantic Ocean. Our results provide persuasive evidence of significant oceanic memory on multi-annual timescales, and are therefore encouraging for the prospects of developing skillful predictions.”

Citation: Jon Robson, Rowan Sutton, Katja Lohmann, Doug Smith and Matthew D. Palmer, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00443.1.

Using Lord Kelvin’s measurements to determine smoke emissions in 1859

Smoke emissions from industrial western Scotland in 1859 inferred from Lord Kelvin’s atmospheric electricity measurements – Aplin (2012)

Abstract: “Lord Kelvin (William Thomson) made careful, calibrated measurements of the atmospheric Potential Gradient (PG) at three sites on the east side of Arran in 1859. The PG was always anomalously high in easterly and north-easterly winds. Positive space charge from sea spray may have contributed to the high PG at two coastal sites, but measurements made on Goatfell, inland and 100-175 m above sea level are unlikely to have been affected by spray. Instead, pollution from the Scottish mainland seems the more likely cause of the high PG at Goatfell, which varied from 300 to 1000 Vm⁻¹ on 10^th-11^th October 1859, corresponding to smoke levels from 0.2 to 0.8 mgm⁻³. Gaussian plume calculations, based on the atmospheric conditions described by Lord Kelvin, and constrained by early Glaswegian pollution measurements, indicate a substantial source region located on the Scottish mainland, 20-40 km from Arran, emitting between 10-10⁴ kgs⁻¹.”

Citation: K.L. Aplin, Atmospheric Environment, http://dx.doi.org/10.1016/j.atmosenv.2011.12.053.

Tropical ectotherms are heading for catastrophe even with modest predicted warming

Degrees of disruption: projected temperature increase has catastrophic consequences for reproduction in a tropical ectotherm – Zeh et al. (2012)

Abstract: “Although climate change models predict relatively modest increases in temperature in the tropics by the end of the century, recent analyses identify tropical ectotherms as the organisms most at risk from climate warming. Because metabolic rate in ectotherms increases exponentially with temperature, even a small rise in temperature poses a physiological threat to tropical ectotherms inhabiting an already hot environment. If correct, the metabolic theory of climate warming has profound implications for global biodiversity, since tropical insects and arachnids constitute the vast majority of animal species. Predicting how climate change will translate into fitness consequences for tropical arthropods requires an understanding of the effects of temperature increase on the entire life history of the species. Here, in a comprehensive case study of the fitness consequences of the projected temperature increase for the tropics, we conducted a split-brood experiment on the neotropical pseudoscorpion, Cordylochernes scorpioides, in which 792 offspring from 33 females were randomly assigned at birth to control- and high-temperature treatments for rearing through the adult stage. The diurnally-varying, control-treatment temperature was determined from long-term, average daily temperature minima and maxima in the pseudoscorpion’s native habitat. In the high-temperature treatment, increasing temperature by the 3.5 °C predicted for the tropics significantly reduced survival and accelerated development at the cost of reduced adult size and a dramatic decrease in level of sexual dimorphism. The most striking effects, however, involved reproductive traits. Reared at high temperature, males produced 45% as many sperm as control males, and females failed to reproduce. Sequencing of the mitochondrial ND2 gene revealed two highly divergent haplogroups that differed substantially in developmental rate and survivorship but not in reproductive response to high temperature. Our findings suggest that reproduction may be the Achilles’ heel of tropical ectotherms, as climate warming subjects them to an increasingly adverse thermal environment.”

Citation: Jeanne A. Zeh, Melvin M. Bonilla, Eleanor J. Su, Michael V. Padua, Rachel V. Anderson, Dilpreet Kaur, Dou-Shuan Yang, David W. Zeh, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02640.x.

Global warming has increased Eurasian snow cover which cools boreal winters

Arctic warming, increasing snow cover and widespread boreal winter cooling – Cohen et al. (2012) [FULL TEXT]

Abstract: “The most up to date consensus from global climate models predicts warming in the Northern Hemisphere (NH) high latitudes to middle latitudes during boreal winter. However, recent trends in observed NH winter surface temperatures diverge from these projections. For the last two decades, large-scale cooling trends have existed instead across large stretches of eastern North America and northern Eurasia. We argue that this unforeseen trend is probably not due to internal variability alone. Instead, evidence suggests that summer and autumn warming trends are concurrent with increases in high-latitude moisture and an increase in Eurasian snow cover, which dynamically induces large-scale wintertime cooling. Understanding this counterintuitive response to radiative warming of the climate system has the potential for improving climate predictions at seasonal and longer timescales.”

Citation: Judah L Cohen et al 2012 Environ. Res. Lett. 7 014007 doi:10.1088/1748-9326/7/1/014007.

Increased cloud cover has slowed summer warming in Eurasia

Damped summer warming accompanied with cloud cover increase over Eurasia from 1982 to 2009 – Tang & Leng (2012) [FULL TEXT]

Abstract: “The relationship between summer temperature, total cloud cover and precipitation over Eurasia was investigated using observation-based products of temperature and precipitation, and satellite-derived cloud cover and radiation products. We used a partial least squares regression approach to separate the local influences of cloud cover and precipitation on temperature variations. Our results suggest that the variance of summer temperature is partly explained by changes in summer cloudiness. The summer temperature dependence on cloud cover is strong at the high latitudes and in the middle latitude semi-humid area, while the dependence on precipitation is strong in the Central Asia arid area and the southern Asia humid area. During the period 1982–2009, the damped warming in extended West Siberia was accompanied with increases in cloud cover, and the pronounced warming in Europe and Mongolia was associated with a decrease in cloud cover and precipitation. Our results suggest that cloud cover may be the important local factor influencing the summer temperature variation in Eurasia while precipitation plays an important role at the middle latitudes.”

Citation: Qiuhong Tang and Guoyong Leng 2012 Environ. Res. Lett. 7 014004 doi:10.1088/1748-9326/7/1/014004.

Study finds no statistically significant changes in Antarctic snowmelt since 1979

Insignificant change in Antarctic snowmelt volume since 1979 – Munneke et al. (2012) [FULL TEXT]

Abstract: “Surface snowmelt is widespread in coastal Antarctica. Satellite-based microwave sensors have been observing melt area and duration for over three decades. However, these observations do not reveal the total volume of meltwater produced on the ice sheet. Here we present an Antarctic melt volume climatology for the period 1979–2010, obtained using a regional climate model equipped with realistic snow physics. We find that mean continent-wide meltwater volume (1979–2010) amounts to 89 Gt y⁻¹ with large interannual variability (σ = 41 Gt y⁻¹). Of this amount, 57 Gt y⁻¹ (64%) is produced on the floating ice shelves extending from the grounded ice sheet, and 71 Gt y⁻¹ in West-Antarctica, including the Antarctic Peninsula. We find no statistically significant trend in either continent-wide or regional meltwater volume for the 31-year period 1979–2010.”

Citation: Kuipers Munneke, P., G. Picard, M. R. van den Broeke, J. T. M. Lenaerts, and E. van Meijgaard (2012), Insignificant change in Antarctic snowmelt volume since 1979, Geophys. Res. Lett., 39, L01501, doi:10.1029/2011GL050207.

Production loss of mollusks due to ocean acidification could be over 100 billion USD

Economic costs of ocean acidification: a look into the impacts on global shellfish production – Narita et al. (2012)

Abstract: “Ocean acidification is increasingly recognized as a major global problem. Yet economic assessments of its effects are currently almost absent. Unlike most other marine organisms, mollusks, which have significant commercial value worldwide, have relatively solid scientific evidence of biological impact of acidification and allow us to make such an economic evaluation. By performing a partial-equilibrium analysis, we estimate global and regional economic costs of production loss of mollusks due to ocean acidification. Our results show that the costs for the world as a whole could be over 100 billion USD with an assumption of increasing demand of mollusks with expected income growths combined with a business-as-usual emission trend towards the year 2100. The major determinants of cost levels are the impacts on the Chinese production, which is dominant in the world, and the expected demand increase of mollusks in today’s developing countries, which include China, in accordance with their future income rise. Our results have direct implications for climate policy. Because the ocean acidifies faster than the atmosphere warms, the acidification effects on mollusks would raise the social cost of carbon more strongly than the estimated damage adds to the damage costs of climate change.”

Citation: Daiju Narita, Katrin Rehdanz and Richard S. J. Tol, Climatic Change, DOI: 10.1007/s10584-011-0383-3.

Analysis of abrupt climate changes during Holocene

Patterns, processes, and impacts of abrupt climate change in a warm world: the past 11,700 years – Shuman (2012)

Abstract: “Abrupt environmental changes punctuated the warm Holocene epoch (the past ∼11,700 years), and studies of these episodes can provide insight into the dynamics that produce rapid climate changes, as well as their ecologic, hydrologic, and geomorphic impacts. This review considers the processes that generated warm world abrupt changes and their landscape and resource effects, including nonlinear climate system interactions, as well as the possibility that large climate variability can linearly produce apparent ‘state shifts.’ Representative examples of Holocene changes illustrate processes that could produce future changes, including (1) rapid changes in ice sheets, such as by ca 8200 years before AD 1950, (2) shifts in the behavior of the El Nino-Southern Oscillation (e.g., at ca 5600 years before AD 1950) and Atlantic Meridional Overturning Circulation (e.g., at ca 2700 years before AD 1950), and (3) land–atmosphere feedbacks, such as were possible in North Africa in the mid-Holocene. These case examples, drawn primarily from the Northern Hemisphere, also reveal the dynamics that generate the types of climate change impacts that would be particularly evident to individuals and societies, such as rapid tree species declines (observed to have taken place within as little time as 6–40 years) and persistent shifts in the regional availability of water. Holocene changes also demonstrate that even progressive climate change can produce important abrupt impacts; that increased rates of background climate forcing may increase the frequency of abrupt responses; and that impacts may well depend upon the particular sequence of changes.”

Citation: Bryan Shuman, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.152.

Tropical oceans were colder sometimes during Paleozoic than during last glacial maximum

Low-latitude Ordovician to Triassic brachiopod habitat temperatures (BHTs) determined from δ¹⁸O_{[brachiopod calcite]} : A cold hard look at ice-house tropical oceans – Giles (2012)

Abstract: “Some researchers have suggested that Phanerozoic land-based ice sheets extended occasionally into the tropical realm. If true, the tropical ocean at those times must have been distinctly colder than at the Last Glacial Maximum (LGM) when northern hemisphere ice sheets did not extend below 38° latitude. Low-latitude ocean temperatures derived from oxygen isotopes of brachiopod shells test this hypothesis by comparing the temperature regime for Paleozoic and early Mesozoic low-latitude settings to the tropical temperature regime of the modern interstadial ocean, and to mean temperatures estimated for the tropical ocean at LGM. A running mean of pH-adjusted brachiopod habitat temperatures (BHTs) shows that Paleozoic low-latitude oceans were, on average, cool to cold relative to the modern interstadial tropical ocean. At times during Pennsylvanian, Serpukhovian, Tournaisian and Ordovician-Silurian glaciations, these tropical seas were indeed significantly colder on average than at the LGM. Ice-sheets within tropical latitudes can be reasonably predicted at those times. Abundant and diverse Paleozoic brachiopod communities reflect these cool tropical oceans, consistent with modern brachiopod ecological preference for colder waters. Amplified Paleozoic temperature oscillations suggest recurring global warming events which episodically drove these cold tropical oceans to temperatures significantly higher than the warmest modern tropical ocean.”

Citation: Peter S. Giles, Palaeogeography, Palaeoclimatology, Palaeoecology, http://dx.doi.org/10.1016/j.palaeo.2012.01.002.

Ice free Arctic Ocean causes more precipitation which slows down glacier mass loss in Svalbard

The impact of a seasonally ice free Arctic Ocean on the temperature, precipitation and surface mass balance of Svalbard – Day et al. (2012) [FULL TEXT, CORRECTION]

Abstract: “The observed decline in summer sea ice extent since the 1970s is predicted to continue until the Arctic Ocean is seasonally ice free during the 21st Century. This will lead to a much perturbed Arctic climate with large changes in ocean surface energy flux. Svalbard, located on the present day sea ice edge, contains many low lying ice caps and glaciers and is expected to experience rapid warming over the 21st Century. The total sea level rise if all the land ice on Svalbard were to melt completely is 0.02 m. The purpose of this study is to quantify the impact of climate change on Svalbard’s surface mass balance (SMB) and to determine, in particular, what proportion of the projected changes in precipitation and SMB are a result of changes to the Arctic sea ice cover. To investigate this a regional climate model was forced with monthly mean climatologies of sea surface temperature (SST) and sea ice concentration for the periods 1961–1990 and 2061–2090 under two emission scenarios. In a novel forcing experiment, 20th Century SSTs and 21st Century sea ice were used to force one simulation to investigate the role of sea ice forcing. This experiment results in a 3.5 m water equivalent increase in Svalbard’s SMB compared to the present day. This is because over 50 % of the projected increase in winter precipitation over Svalbard under the A1B emissions scenario is due to an increase in lower atmosphere moisture content associated with evaporation from the ice free ocean. These results indicate that increases in precipitation due to sea ice decline may act to moderate mass loss from Svalbard’s glaciers due to future Arctic warming.”

Citation: Day, J. J., Bamber, J. L., Valdes, P. J., and Kohler, J.: The impact of a seasonally ice free Arctic Ocean on the temperature, precipitation and surface mass balance of Svalbard, The Cryosphere, 6, 35-50, doi:10.5194/tc-6-35-2012, 2012.

South Asia extreme temperature indices show general warming only in low altitudes and latitudes

Impact of altitude and latitude on changes in temperature extremes over South Asia during 1971–2000 – Revadekar et al. (2012)

Abstract: “South Asia covers more than 30° of latitude with weather observation stations situated from 6°N at Galle, Sri Lanka, to 36°N at Chitral in Pakistan. Moreover, the South Asian station network ranges in altitude from sea level to nearly 4000 m above sea level. This paper uses time series of 11 objectively defined indices of daily temperature extremes at 197 stations in Bangladesh, India, Nepal, Pakistan and Sri Lanka to examine the possible impacts of elevation and latitude on changes in temperature extremes over the period of 1971–2000. Trends in extreme indices are consistent with general warming only at low altitudes and latitudes. Stations at high altitudes and latitudes show both positive and negative trends in extreme temperature indices. As a notable example, the Diurnal Temperature Range (DTR), which has been known to decrease in most parts of the globe, has increasing trends over many high altitude stations in South Asia. Trends in extreme temperature indices at stations in South Asia higher than 2000 m above sea level are mostly in disagreement with those reported over the Tibetan Plateau. Observed trends at low altitude locations in South Asia suggest that these sites can generally expect future changes in temperature extremes that are consistent with broad-scale warming. High-elevation sites appear to be more influenced by local factors and, hence, future changes in temperature extremes may be less predictable for these locations.”

Citation: J. V. Revadekar, S. Hameed, D. Collins, M. Manton, M. Sheikh, H. P. Borgaonkar, D. R. Kothawale, M. Adnan, A. U. Ahmed, J. Ashraf, S. Baidya, N. Islam, D. Jayasinghearachchi, N. Manzoor, K. H. M. S. Premalal, M. L. Shreshta, International Journal of Climatology, DOI: 10.1002/joc.3418.

Greenland ice core shows that 1783 Laki volcanic plume did not reach stratosphere

Sulfur isotope evidence of little or no stratospheric impact by the 1783 Laki volcanic eruption – Lanciki et al. (2012)

Abstract: “Historic records and research have suggested that the 1783–1784 eruption of the Laki fissure volcano in Iceland impacted Northern Hemisphere climate significantly, probably as a result of the direct injection of volcanic materials into the stratosphere where the volcanic aerosols would linger for years to cause surface cooling across the Northern Hemisphere. However, recent modeling work indicates the Laki climatic impact was limited to the Northern Hemisphere and only in the second half of 1783. We measured sulfur-33 isotope excess (Δ³³S) in volcanic sulfate of historical eruptions including Laki found in Summit, Greenland ice cores. No Δ³³S excess is found in sulfate of apparently tropospheric eruptions, while sulfate of stratospheric eruptions is characterized by significant Δ³³S excess and a positive-to-negative change in Δ³³S during its gradual removal from the atmosphere. Because the same characteristics have been previously found in volcanic sulfate in Antarctica snow, the results from Greenland indicate similar global processes of stratospheric chemical conversion of SO₂ to sulfate. The isotopic composition of Laki sulfate is essentially normal and shows no characteristics of sulfate produced by stratospheric photochemical reactions. This clearly indicates that the Laki plume did not reach altitudes of the stratospheric ozone layer. Further, the short aerosol residence time (<6 months) suggests that the bulk of the Laki plume and subsequent aerosols were probably confined to the middle and upper troposphere. These conclusions support the hypothesis of D’Arrigo and colleagues that the unusually cold winter of 1783–1784 was not caused by Laki.”

Citation: Lanciki, A., J. Cole-Dai, M. H. Thiemens, and J. Savarino (2012), Sulfur isotope evidence of little or no stratospheric impact by the 1783 Laki volcanic eruption, Geophys. Res. Lett., 39, L01806, doi:10.1029/2011GL050075.

Improved constraints lead to relatively low projections of 21st century warming

Improved constraints on 21st-century warming derived using 160 years of temperature observations – Gillett et al. (2012)

Abstract: “Projections of 21st century warming may be derived by using regression-based methods to scale a model’s projected warming up or down according to whether it under- or over-predicts the response to anthropogenic forcings over the historical period. Here we apply such a method using near surface air temperature observations over the 1851–2010 period, historical simulations of the response to changing greenhouse gases, aerosols and natural forcings, and simulations of future climate change under the Representative Concentration Pathways from the second generation Canadian Earth System Model (CanESM2). Consistent with previous studies, we detect the influence of greenhouse gases, aerosols and natural forcings in the observed temperature record. Our estimate of greenhouse-gas-attributable warming is lower than that derived using only 1900–1999 observations. Our analysis also leads to a relatively low and tightly-constrained estimate of Transient Climate Response of 1.3–1.8°C, and relatively low projections of 21st-century warming under the Representative Concentration Pathways. Repeating our attribution analysis with a second model (CNRM-CM5) gives consistent results, albeit with somewhat larger uncertainties.”

Citation: Gillett, N. P., V. K. Arora, G. M. Flato, J. F. Scinocca, and K. von Salzen (2012), Improved constraints on 21st-century warming derived using 160 years of temperature observations, Geophys. Res. Lett., 39, L01704, doi:10.1029/2011GL050226.

Sea level rise and vertical land motion in southern Europe coast

Coastal sea level rise in southern Europe and the nonclimate contribution of vertical land motion – Wöppelmann & Marcos (2012)

Abstract: “In this study, we extend the advanced approach of combining tide gauge and satellite altimetry data with supplemental equations from adjacent tide gauge records of at least 30 years of common data to investigate the relative importance of the nonclimate contribution of vertical land movement to the observed rates of sea level change along the coasts of southern Europe. The sensitivity tests proved that the advanced approach is robust and accurate at the submillimeter per year level of around 0.4 mm yr⁻¹ in estimating rates of vertical land movements. It enabled identifying stations displaying large rates of vertical land movements that must be taken into account when predicting future sea level rise and appraising the exposure to its impacts on populations and assets. The average rate of coastal climate-related sea level rise in the Mediterranean Sea was consequently revisited to be of 1.7 mm yr⁻¹ over the past century, whereas the Atlantic northern Iberian coast revealed a significant high rate of sea level rise in excess of 3.4 mm yr⁻¹ for the past 70 years. Future work should consider applying this powerful approach to other geographic contexts as a useful source of supplementary data for geodynamic studies.”

Citation: Wöppelmann, G., and M. Marcos (2012), Coastal sea level rise in southern Europe and the nonclimate contribution of vertical land motion, J. Geophys. Res., 117, C01007, doi:10.1029/2011JC007469.

CLASSIC OF THE WEEK: Langley (1876)

Measurement of the Direct Effect of Sun-spots on Terrestrial Climates – Langley (1876) [FULL TEXT]

No abstract. In this paper, Samuel Langley (who made the measurements Arrhenius used in his legendary paper) calculates that the effect of sun-spots to the temperature of Earth is between 0.063 and 0.29 degrees Celsius.

Citation: Langley, S. P., 1876, Monthly Notices of the Royal Astronomical Society, Vol. 37, p.5.

Calibrating the End-Permian Mass Extinction – Shen et al. (2011) “The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (‰) in δ¹³C over 90,000 years, and coincided with a δ¹³C excursion of −5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.” Shu-zhong Shen, James L. Crowley, Yue Wang, Samuel A. Bowring, Douglas H. Erwin, Peter M. Sadler, Chang-qun Cao, Daniel H. Rothman, Charles M. Henderson, Jahandar Ramezani, Hua Zhang, Yanan Shen, Xiang-dong Wang, Wei Wang, Lin Mu, Wen-zhong Li, Yue-gang Tang, Xiao-lei Liu, Lu-jun Liu, Yong Zeng, Yao-fa Jiang, Yu-gan Jin, Science 9 December 2011: Vol. 334 no. 6061 pp. 1367-1372, DOI: 10.1126/science.1213454.

Carbon-isotope stratigraphy across the Permian–Triassic boundary: A review – Korte & Kozur (2010) “The Palaeozoic–Mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon-isotope excursion at the Permian–Triassic (P–T) boundary, well known from a plethora of marine and continental sediments. Potential causes for this negative δ¹³C trend (and their links to the latest Permian mass extinction) have been intensively debated in the literature. In order to draw conclusions regarding causation, a general δ¹³C curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background. The most important features of the P–T carbon-isotope trend are the following: the 4–7‰ δ¹³C decline (lasting ∼500,000 years) is gradual and began in the Changhsingian at the stratigraphic level of the C. bachmanni Zone. The decreasing trend is interrupted by a short-term positive event that starts at about the latest Permian low-latitude marine main extinction event horizon (=EH), indicating that the extinction itself cannot have caused the negative carbon-isotope excursion. After this short-term positive excursion, the δ¹³C decline continues to a first minimum at about the P–T boundary. A subsequent slight increase is followed by a second (occasionally two-peaked) minimum in the lower (and middle) I. isarcica Zone. The negative carbon-isotope excursion was most likely a consequence of a combination of different causes that may include: (1) direct and indirect effects of the Siberian Trap and contemporaneous volcanism and (2) anoxic deep waters occasionally reaching very shallow sea levels. A sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon-isotope trend is questionable at least for the time span a little below the EH and somewhat above the P–T boundary.” Christoph Korte, Heinz W. Kozur, Journal of Asian Earth Sciences, Volume 39, Issue 4, 9 September 2010, Pages 215-235, doi:10.1016/j.jseaes.2010.01.005.

Massive volcanism at the Permian–Triassic boundary and its impact on the isotopic composition of the ocean and atmosphere – Korte et al. (2010) “Bulk carbonate and conodonts from three Permian–Triassic (P–T) boundary sections at Guryul Ravine (Kashmir), Abadeh (central Iran) and Pufels/Bula/Bulla (Italy) were investigated for δ¹³C and δ¹⁸O. Carbon isotope data highlight environmental changes across the P–T boundary and show the following features: (1) a gradual decrease of ∼4‰ to more than 7‰ starting in the Late Permian (Changhsingian) C. bachmanni Zone, with two superimposed transient positive excursions in the C. meishanensis–H. praeparvus and the M. ultima–S. ? mostleri Zones; (2) two δ¹³C minima, the first at the P–T boundary and a higher, occasionally double-minimum in the lower I. isarcica Zone. It is unlikely that the short-lived phenomena, such as a breakdown in biological productivity due to catastrophic mass extinction, a sudden release of oceanic methane hydrates or meteorite impact(s), could have been the main control on the latest Permian carbon isotope curve because of its prolonged (0.5 Ma) duration, gradual decrease and the existence of a >1‰ positive shift at the main extinction horizon. The P–T boundary δ¹³C trend matches in time and magnitude the eruption of the Siberian Traps and other contemporaneous volcanism, suggesting that volcanogenic effects, such as outgassed CO2 from volcanism and, even more, thermal metamorphism of organic-rich sediments, as the likely cause of the negative trend.” Christoph Korte, Prabhas Pande, P. Kalia, Heinz W. Kozur, Michael M. Joachimski, Hedi Oberhänsli, Journal of Asian Earth Sciences, Volume 37, Issue 4, 1 March 2010, Pages 293-311, doi:10.1016/j.jseaes.2009.08.012.

Illawarra Reversal: The fingerprint of a superplume that triggered Pangean breakup and the end-Guadalupian (Permian) mass extinction – Isozaki (2009) “The Permian magnetostratigraphic record demonstrates that a remarkable change in geomagnetism occurred in the Late Guadalupian (Middle Permian; ca. 265 Ma) from the long-term stable Kiaman Reverse Superchron (throughout the Late Carboniferous and Early-Middle Permian) to the Permian–Triassic Mixed Superchron with frequent polarity changes (in the Late Permian and Triassic). This unique episode called the Illawarra Reversal probably reflects a significant change in the geodynamo in the outer core of the planet after a 50 million years of stable geomagnetism. The Illawarra Reversal was likely led by the appearance of a thermal instability at the 2900 km-deep core–mantle boundary in connection with mantle superplume activity. The Illawarra Reversal and the Guadalupian–Lopingian boundary event record the significant transition processes from the Paleozoic to Mesozoic–Modern world. One of the major global environmental changes in the Phanerozoic occurred almost simultaneously in the latest Guadalupian, as recorded in 1) mass extinction, 2) ocean redox change, 3) sharp isotopic excursions (C and Sr), 4) sea-level drop, and 5) plume-related volcanism. In addition to the claimed possible links between the above-listed environmental changes and mantle superplume activity, I propose here an extra explanation that a change in the core’s geodynamo may have played an important role in determining the course of the Earth’s surface climate and biotic extinction/evolution. When a superplume is launched from the core–mantle boundary, the resultant thermal instability makes the geodynamo’s dipole of the outer core unstable, and lowers the geomagnetic intensity. Being modulated by the geo- and heliomagnetism, the galactic cosmic ray flux into the Earth’s atmosphere changes with time. The more cosmic rays penetrate through the atmosphere, the more clouds develop to increase the albedo, thus enhancing cooling of the Earth’s surface. The Illawarra Reversal, the Kamura cooling event, and other unique geologic phenomena in the Late Guadalupian are all concordantly explained as consequences of the superplume activity that initially triggered the breakup of Pangea. The secular change in cosmic radiation may explain not only the extinction-related global climatic changes in the end-Guadalupian but also the long-term global warming/cooling trend in Earth’s history in terms of cloud coverage over the planet.” Yukio Isozaki, Gondwana Research, Volume 15, Issues 3-4, June 2009, Pages 421-432, Special Issue: Supercontinent Dynamics, doi:10.1016/j.gr.2008.12.007.

Elevated atmospheric CO₂ and the delayed biotic recovery from the end-Permian mass extinction – Fraiser & Bottjer (2007) “Excessive CO₂ in the Earth ocean–atmosphere system may have been a significant factor in causing the end-Permian mass extinction. CO₂ injected into the atmosphere by the Siberian Traps has been postulated as a major factor leading to the end-Permian mass extinction by facilitating global warming, widespread ocean stratification, and development of anoxic, euxinic and CO₂-rich deep waters. A broad incursion of this toxic deep water into the surface ocean may have caused this mass extinction. Although previous studies of the role of excessive CO₂ have focused on these “bottom-up” effects emanating from the deep ocean, “top-down” effects of increasing atmosphere CO₂ concentrations on ocean-surface waters and biota have not previously been explored. Passive diffusion of atmospheric CO₂ into ocean-surface waters decreases the pH and CaCO₃ saturation state of seawater, causing a physiological and biocalcification crisis for many marine invertebrates. While both “bottom-up” and “top-down” mechanisms may have contributed to the relatively short-term biotic devastation of the end-Permian mass extinction, such a “top-down” physiological and biocalcification crisis would have had long-term effects and might have contributed to the protracted 5- to 6-million-year-long delay in biotic recovery following this mass extinction. Earth’s Modern marine biota may experience similar “top-down” CO₂ stresses if anthropogenic input of atmosphere/ocean CO₂ continues to rise.” Margaret L. Fraiser, David J. Bottjer, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 252, Issues 1-2, 20 August 2007, Pages 164-175, The Permian-Triassic Boundary Crisis and Early Triassic Biotic Recovery, doi:10.1016/j.palaeo.2006.11.041.

Paleophysiology and end-Permian mass extinction – Knoll et al. (2007) “Physiological research aimed at understanding current global change provides a basis for evaluating selective survivorship associated with Permo-Triassic mass extinction. Comparative physiology links paleontological and paleoenvironmental observations, supporting the hypothesis that an end-Permian trigger, most likely Siberian Trap volcanism, touched off a set of physically-linked perturbations that acted synergistically to disrupt the metabolisms of latest Permian organisms. Global warming, anoxia, and toxic sulfide probably all contributed to end-Permian mass mortality, but hypercapnia (physiological effects of elevated P_CO2) best accounts for the selective survival of marine invertebrates. Paleophysiological perspectives further suggest that persistent or recurring hypercapnia/global warmth also played a principal role in delayed Triassic recovery. More generally, physiology provides an important way of paleobiological knowing in the age of Earth system science.” Andrew H. Knoll, Richard K. Bambach, Jonathan L. Payne, Sara Pruss, Woodward W. Fischer, Earth and Planetary Science Letters, Volume 256, Issues 3-4, 30 April 2007, Pages 295-313, doi:10.1016/j.epsl.2007.02.018. [Full text]

End-Permian mass extinction pattern in the northern peri-Gondwanan region – Shen et al. (2007) “The Permian-Triassic extinction pattern in the peri-Gondwanan region is documented biostratigraphically, geochemically and sedimentologically based on three marine sequences deposited in southern Tibet and comparisons with the sections in the Salt Range, Pakistan and Kashmir. Results of biostratigraphical ranges for the marine faunas reveal an end-Permian event comparable in timing with that known at the Meishan section in low palaeolatitude as well as Spitsbergen and East Greenland in northern Boreal settings although biotic patterns earlier in the Permian vary. The previously interpreted delayed extinction (Late Griesbachian) at the Selong Xishan section is not supported by our analysis. The end-Permian event exhibits an abrupt marine faunal shift slightly beneath the Permian-Triassic boundary (PTB) from benthic taxa- to nektic taxa-dominated communities. The climate along the continental margin of Neo-Tethys was cold before the extinction event. However, a rapid climatic warming event as indicated by the southward invasion of abundant warm-water conodonts, warm-water brachiopods, calcareous sponges, and gastropods was associated with the extinction event. Stable isotopic values of δ¹³Ccarb, δ¹³Corg and δ¹⁸O show a sharp negative drop slightly before and during the extinction interval. Sedimentological and microstratigraphical analysis reveals a Late Permian regression, as marked by a Caliche Bed at the Selong Xishan section and the micaceous siltstone in the topmost part of the Qubuerga Formation at the Qubu and Tulong sections. The regression was immediately followed by a rapid transgression beneath the PTB. The basal Triassic rocks fine upward, and are dominated by dolomitic packstone/wackestone containing pyritic cubes, bioturbation and numerous tiny foraminifers, suggesting that the studied sections were deposited during the initial stage of the transgression and hence may not have been deeply affected by the anoxic event that is widely believed to characterise the zenith of the transgression.” Shu Zhong Shen, Chang-Qun Cao, Charles M. Henderson, Xiang-Dong Wang, Guang R. Shi, Yue Wang, Wei Wang, Palaeoworld, Volume 15, Issue 1, January 2006, Pages 3-30, doi:10.1016/j.palwor.2006.03.005. [Full text]

Middle-Late Permian mass extinction on land – Retallack et al. (2006) “The end-Permian mass extinction has been envisaged as the nadir of biodiversity decline due to increasing volcanic gas emissions over some 9 million years. We propose a different tempo and mechanism of extinction because we recognize two separate but geologically abrupt mass extinctions on land, one terminating the Middle Permian (Guadalupian) at 260.4 Ma and a later one ending the Permian Period at 251 Ma. Our evidence comes from new paleobotanical, paleopedological, and carbon isotopic studies of Portal Mountain, Antarctica, and comparable studies in the Karoo Basin, South Africa. Extinctions have long been apparent among marine invertebrates at both the end of the Guadalupian and end of the Permian, which were also times of warm-wet greenhouse climatic transients, marked soil erosion, transition from high- to low-sinuosity and braided streams, soil stagnation in wetlands, and profound negative carbon isotope anomalies. Both mass extinctions may have resulted from catastrophic methane outbursts to the atmosphere from coal intruded by feeder dikes to flood basalts, such as the end-Guadalupian Emeishan Basalt and end-Permian Siberian Traps.” Gregory J. Retallack, Christine A. Metzger, Tara Greaver, A. Hope Jahren, Roger M.H. Smith and Nathan D. Sheldon, GSA Bulletin, v. 118 no. 11-12 p. 1398-1411, doi: 10.1130/B26011.1. [Full text]

Climate simulation of the latest Permian: Implications for mass extinction – Kiehl & Shields (2005) “Life at the Permian-Triassic boundary (ca. 251 Ma) underwent the largest disruption in Earth’s history. Paleoclimatic data indicate that Earth was significantly warmer than present and that much of the ocean was anoxic or euxinic for an extended period of time. We present results from the first fully coupled comprehensive climate model using paleogeography for this time period. The coupled climate system model simulates warm high-latitude surface air temperatures related to elevated carbon dioxide levels and a stagnate global ocean circulation in concert with paleodata indicating low oxygen levels at ocean depth. This is the first climate simulation that captures these observed features of this time period.” Jeffrey T. Kiehl and Christine A. Shields, Geology, v. 33 no. 9 p. 757-760, doi: 10.1130/G21654.1. [Full text]

How to kill (almost) all life: the end-Permian extinction event – Benton & Twitchett (2003) “The biggest mass extinction of the past 600 million years (My), the end-Permian event (251 My ago), witnessed the loss of as much as 95% of all species on Earth. Key questions for biologists concern what combination of environmental changes could possibly have had such a devastating effect, the scale and pattern of species loss, and the nature of the recovery. New studies on dating the event, contemporary volcanic activity, and the anatomy of the environmental crisis have changed our perspectives dramatically in the past five years. Evidence on causation is equivocal, with support for either an asteroid impact or mass volcanism, but the latter seems most probable. The extinction model involves global warming by 6°C and huge input of light carbon into the ocean-atmosphere system from the eruptions, but especially from gas hydrates, leading to an ever-worsening positive-feedback loop, the ‘runaway greenhouse’.” Michael J. Benton, Richard J. Twitchett, Trends in Ecology & Evolution, Volume 18, Issue 7, July 2003, Pages 358-365, doi:10.1016/S0169-5347(03)00093-4. [Full text]

Land-plant diversity and the end-Permian mass extinction – Rees (2002) “The Permian and Triassic represent a time of major global climate change from icehouse to hothouse conditions and significant (∼25°) northward motion of landmasses amalgamated in essentially one supercontinent, Pangea. The greatest of all mass extinctions occurred around the Permian-Triassic boundary (251 Ma), although there is no consensus regarding the cause(s). Recent studies have suggested a meteor impact and worldwide die-off of vegetation, on the basis of sparse local observations. However, new analyses of global Permian and Triassic plant data in a paleogeographic context show that the scale and timing of effects varied markedly between regions. The patterns are best explained by differences in geography, climate, and fossil preservation, not by catastrophic events. Caution should be exercised when extrapolating local observations to global-scale interpretations. At the other extreme, global compilations of biotic change through time can be misleading if the effects of geography, climate, and preservation bias are not considered.” P. McAllister Rees, Geology, v. 30 no. 9 p. 827-830, doi: 10.1130/0091-7613(2002)​030​2.0.CO;2. [Full text]

Ocean stagnation and end-Permian anoxia – Hotinski et al. (2001) “Ocean stagnation has been invoked to explain the widespread occurrence of organic-carbon–rich, laminated sediments interpreted to have been deposited under anoxic bottom waters at the time of the end-Permian mass extinction. However, to a first approximation, stagnation would severely reduce the upwelling supply of nutrients to the photic zone, reducing productivity. Moreover, it is not obvious that ocean stagnation can be achieved. Numerical experiments performed with a three-dimensional global ocean model linked to a biogeochemical model of phosphate and oxygen cycling indicate that a low equator to pole temperature gradient could have produced weak oceanic circulation and widespread anoxia in the Late Permian ocean. We find that polar warming and tropical cooling of sea-surface temperatures cause anoxia throughout the deep ocean as a result of both lower dissolved oxygen in bottom source waters and increased nutrient utilization. Buildup of quantities of H₂S and CO₂ in the Late Permian ocean sufficient to directly cause a mass extinction, however, would have required large increases in the oceanic nutrient inventory.” Roberta M. Hotinski, Karen L. Bice, Lee R. Kump, Raymond G. Najjar and Michael A. Arthur, Geology, v. 29 no. 1 p. 7-10, doi: 10.1130/0091-7613(2001)​029​2.0.CO;2. [Full text]

Pattern of Marine Mass Extinction Near the Permian-Triassic Boundary in South China – Jin et al. (2000) “The Meishan section across the Permian-Triassic boundary in South China is the most thoroughly investigated in the world. A statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251.4 million years ago, coincident with a dramatic depletion of δ¹³C_carbonate and an increase in microspherules.” Y. G. Jin, Y. Wang, W. Wang, Q. H. Shang, C. Q. Cao and D. H. Erwin, Science 21 July 2000: Vol. 289 no. 5478 pp. 432-436, DOI: 10.1126/science.289.5478.432. [Full text]

U/Pb Zircon Geochronology and Tempo of the End-Permian Mass Extinction – Bowring et al. (1998) “The mass extinction at the end of the Permian was the most profound in the history of life. Fundamental to understanding its cause is determining the tempo and duration of the extinction. Uranium/lead zircon data from Late Permian and Early Triassic rocks from south China place the Permian-Triassic boundary at 251.4 ± 0.3 million years ago. Biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the Changhsingian pulse of the end-Permian extinction, corresponding to the disappearance of about 85 percent of marine species, lasted less than 1 million years. At Meishan, a negative excursion in δ¹³C at the boundary had a duration of 165,000 years or less, suggesting a catastrophic addition of light carbon.” S. A. Bowring, D. H. Erwin, Y. G. Jin, M. W. Martin, K. Davidek and W. Wang, Science 15 May 1998: Vol. 280 no. 5366 pp. 1039-1045, DOI: 10.1126/science.280.5366.1039.

Oceanic Anoxia and the End Permian Mass Extinction – Wignall & Twitchett (1996) “Data on rocks from Spitsbergen and the equatorial sections of Italy and Slovenia indicate that the world’s oceans became anoxic at both low and high paleolatitudes in the Late Permian. Such conditions may have been responsible for the mass extinction at this time. This event affected a wide range of shelf depths and extended into shallow water well above the storm wave base.” Paul B. Wignall, Richard J. Twitchett, Science 24 May 1996: Vol. 272 no. 5265 pp. 1155-1158, DOI: 10.1126/science.272.5265.1155.

Comparative Earth History and Late Permian Mass Extinction – Knoll et al. (1996) “The repeated association during the late Neoproterozoic Era of large carbon-isotopic excursions, continental glaciation, and stratigraphically anomalous carbonate precipitation provides a framework for interpreting the reprise of these conditions on the Late Permian Earth. A paleoceanographic model that was developed to explain these stratigraphically linked phenomena suggests that the overturn of anoxic deep oceans during the Late Permian introduced high concentrations of carbon dioxide into surficial environments. The predicted physiological and climatic consequences for marine and terrestrial organisms are in good accord with the observed timing and selectivity of Late Permian mass extinction.” A. H. Knoll, R. K. Bambach, D. E. Canfield, J. P. Grotzinger, Science 26 July 1996: Vol. 273 no. 5274 pp. 452-457, DOI: 10.1126/science.273.5274.452.

Synchrony and Causal Relations Between Permian-Triassic Boundary Crises and Siberian Flood Volcanism – Renne et al. (1995) “The Permian-Triassic boundary records the most severe mass extinctions in Earth’s history. Siberian flood volcanism, the most profuse known such subaerial event, produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less. Analysis of ⁴⁰Ar/³⁹Ar data from two tuffs in southern China yielded a date of 250.0 ± 0.2 million years ago for the Permian-Triassic boundary, which is comparable to the inception of main stage Siberian flood volcanism at 250.0 ± 0.3 million years ago. Volcanogenic sulfate aerosols and the dynamic effects of the Siberian plume likely contributed to environmental extrema that led to the mass extinctions.” Paul R. Renne, Michael T. Black, Zhang Zichao, Mark A. Richards and Asish R. Basu, Science 8 September 1995: Vol. 269 no. 5229 pp. 1413-1416, DOI: 10.1126/science.269.5229.1413. [Full text]

Synchronism of the Siberian Traps and the Permian-Triassic Boundary – Campbell et al. (1992) “Uranium-lead ages from an ion probe were taken for zircons from the ore-bearing Noril’sk I intrusion that is comagmatic with, and intrusive to, the Siberian Traps. These values match, within an experimental error of ±4 million years, the dates for zircons extracted from a tuff at the Permian-Triassic (P-Tr) boundary. The results are consistent with the hypothesis that the P-Tr extinction was caused by the Siberian basaltic flood volcanism. It is likely that the eruption of these magmas was accompanied by the injection of large amounts of sulfur dioxide into the upper atmosphere, which may have led to global cooling and to expansion of the polar ice cap. The P-Tr extinction event may have been caused by a combination of acid rain and global cooling as well as rapid and extreme changes in sea level resulting from expansion of the polar ice cap.” I. H. Campbell, G. K. Czamanske, V. A. Fedorenko, R. I. Hill and V. Stepanov, Science 11 December 1992: Vol. 258 no. 5089 pp. 1760-1763, DOI: 10.1126/science.258.5089.1760.

The End-Permian mass extinction: What really happened and did it matter? – Erwin (1989) “Marine communities of the Paleozoic differ markedly from those of the post-Paleozoic, a dichotomy long recognized as the most fundamental change between the Cambrian metazoan radiation and the present. The end-Permian mass extinction of about 54% of marine families eliminated many of the groups that dominated Paleozoic communities. Correlative changes occurred in terrestrial vertebrate and plant communities, but there is no clear evidence that these changes are related to the marine extinction. The marine extinction occurred during a period of physical change, and a variety of extinction mechanisms have been proposed, most related to a major Late Permian marine regression or to climatic changes. Unfortunately, the regression has made it difficult to gather data on the rate, timing and pattern of extinction, and the available data exclude only a few hypotheses. Thus the largest mass extinction, and the one with the greatest evolutionary importance, is also the most poorly understood.” Douglas H. Erwin, Trends in Ecology & Evolution, Volume 4, Issue 8, August 1989, Pages 225–229, http://dx.doi.org/10.1016/0169-5347(89)90165-1.

In this week’s papers El Niño does some moonlighting in Europe. In New Zealand they found some unused sea level measurement stations while in Netherlands they apparently run out of official weather stations and started using weather amateur stations. The pines from Spain are showing the decline, but are doing so selectively. In Australia, they apparently didn’t notice YD event at all. There’s yet another effort with cosmic ray and climate connection. We also learn how to tell apart climate signal and noise. But did you know that female corals don’t like climate change? Or that some Malaria species do seem to like it at least in Thar Desert? This is not all, we have studies also on Paris-London westerly index, dark aerosols, inland waters, and carbon in Siberia. However, this is just a scratch of the surface as there are hundreds of papers published every week relating to climate.

AGW Observer takes over Skeptical Science!

From now on, this “New research from last week” series will also be published in Skeptical Science. This has also prompted me to change the outlook of this post a little, as you can see above and below.

El Niño fiddles with European and North Atlantic weather

Central Pacific El Niño, the “subtropical bridge,” and Eurasian climate – Graf & Zanchettin (2012)

Abstract: “This study contributes to the discussion on possible effects of El Niño on North Atlantic/European regional climates. We use NCEP/NCAR reanalysis data to show how the two different types of El Niños (the central Pacific, or CP, and the east Pacific, or EP) result in remarkably different European winter temperature anomalies, specifically weak warming during EP and significant cooling during CP El Niños, the latter being associated with a negative phase of the winter North Atlantic Oscillation (NAO). Our results diverge from former suggestions addressing the weakened stratospheric polar vortex as the dominant factor contributing to the El Niño/NAO teleconnection. We propose a tropospheric bridge as the mechanism primarily responsible for the establishment of a negative NAO phase and of associated cold European winters. This mechanism includes the subtropical jet (STJ) waveguide being activated only during CP El Niños, when anomalous convective heating occurs near the edge of the Pacific warm pool. Under these conditions the STJ is enhanced by planetary wave flux divergence in the subtropical upper troposphere, providing favorable conditions for the propagation of a wave number 5 disturbance around the subtropical Northern Hemisphere. This wave contributes to weakening of the Azores High and, hence, to the negative NAO phase. As global warming scenarios project an increase in the frequency of CP El Niño events, the distinctive nature of this mechanism implies that the probability of cold European winters may increase as well in future decades.”

Citation: Graf, H.-F., and D. Zanchettin (2012), J. Geophys. Res., 117, D01102, doi:10.1029/2011JD016493.

Improvements to sea level trend analysis in New Zealand

Regional sea level trends in New Zealand – Hannah & Bell (2012)

Abstract: “In terms of sea level data sets able to be used for long-term sea level trend analysis, the Southern Hemisphere is a data sparse region of the world. New Zealand lies in this region, presently having four (major port) data sets used for such trend analysis. This paper describes the process followed to compute new sea level trends at another six ports, each with very discontinuous tide gauge records. In each case the tide gauge has previously only been used for precisely defining an historical local Mean Sea Level (MSL) datum. The process used involved a comparison of the old MSL datum with a newly defined datum obtained from sea level data covering the last decade. A simple linear trend was fitted between the two data points. Efforts were then made to assess possible bias in the results due to oceanographic factors such as the El Niño–Southern Oscillation (ENSO) cycle, and the Interdecadal Pacific Oscillation (IPO). This was done by taking the longer time series from the four major ports and assessing the spatially coherent variability in annual sea level using the dominant principal component from an empirical orthogonal function (EOF) analysis. The average relative sea level rise calculated from these six newly derived trends was 1.7 ± 0.1 mm yr⁻¹, a result that is completely consistent with the analysis of the long-term gauge records. Most importantly, it offers a relatively simple method of improving our knowledge of relative sea level trends in data sparse regions of the world.”

Citation: Hannah, J., and R. G. Bell (2012), J. Geophys. Res., 117, C01004, doi:10.1029/2011JC007591.

Weather stations of Dutch weather amateurs used in urban heat island study

Estimating the Urban Heat Island in residential areas in the Netherlands using observations by weather amateurs – Wolters & Brandsma (2012)

Abstract: “A better quantification of the urban heat islands in the Netherlands is urgent, due to heat stress related problems in the recent past combined with the expected temperature rise for the coming decades. However, professional temperature observations in Dutch urban areas are scarce. Therefore, in this research we have explored the use of observations from weather stations installed and maintained by weather amateurs. From a set of over 200 stations, suitable and representative data have been selected from 20 stations, using a set of objective selection criteria based on metadata. One year of data (Jan-Dec 2010) was considered. From these data we have obtained estimates of the magnitude of the UHI in Dutch low-rise residential areas. A positive relation (linear model r-squared ≈ 0.7) was derived between the summer-averaged UHI and the (neighborhood-scale) population density around the observational sites. It was found that the UHI in summer is strongest in nighttime conditions, and increases with decreasing wind speed and decreasing cloud cover, and with increasing sea level air pressure. The summer-averaged UHI was around 0.9°C. During nighttime in a relatively warm one-month subperiod of the summer the average UHI was around 1.4°C. During spring and autumn the UHI was lower than in summer, during winter no significant UHI was observed. The agreement in results between the different stations, and the accordance of the magnitude and variation of the observed UHI to literature, show that automatic observations from weather amateurs can be sufficient quality for atmospheric research, provided that detailed metadata are available.”

Citation: Dirk Wolters and Theo Brandsma, Journal of Applied Meteorology and Climatology 2012, doi: http://dx.doi.org/10.1175/JAMC-D-11-0135.1.

Spanish pines are selective in showing the decline

Selective drought-induced decline of pine species in southeastern Spain – Sánchez-Salguero et al. (2012)

Abstract: “The negative impacts of severe drought on the growth and vigor of tree species and their relationship with forest decline have not been properly evaluated taking into account the differential responses to such stress of trees, sites and species. We evaluated these responses by quantifying the changes in radial growth of plantations of four pine species (Pinus sylvestris, Pinus nigra, Pinus pinaster, Pinus halepensis) which showed distinct decline and defoliation levels in southeastern Spain. We used dendrochronological methods, defoliation records, linear mixed models of basal area increment and dynamic factor analysis to quantify the responses of trees at the species and individual scales to site conditions and drought stress. In the region a temperature rise and a decrease in spring precipitation have led to drier conditions during the late twentieth century characterized by severe droughts in the 1990s and 2000s. As expected, the defoliation levels and the reductions in basal area increment were higher in those species more vulnerable to drought-induced xylem embolism (P. sylvestris) than in those more resistant (P. halepensis). Species adapted to xeric conditions but with high growth rates, such as P. pinaster, were also vulnerable to drought-induced decline. The reduction in basal area increment and the defoliation events occurred after consecutive severe droughts. A decrease in spring precipitation, which is the main driver of radial growth, is the most plausible cause of recent forest decline. The sharp growth reduction and widespread defoliation of the most affected pine plantations of Scots pine make their future persistence in drought-prone sites unlikely under the forecasted warmer and drier conditions.”

Citation: Raúl Sánchez-Salguero, Rafael M. Navarro-Cerrillo, J. Julio Camarero and Ángel Fernández-Cancio, Climatic Change, DOI: 10.1007/s10584-011-0372-6.

Two other studies were published last week on pine tree rings:

- Common growth signal and spatial synchrony of the chronologies of tree-rings from pines in the Baltic Sea region over the last nine centuries – Läänelaid et al. (2012)

- The tree-ring chronology of Scots pine (Pinus sylvestris L.) from the Nesvizh castle XVI–XIX cc. in central Belarus – Yermokhin (2012)

Younger Dryas cooling apparently didn’t show up in Australian region

The Younger Dryas: relevant in the Australian region? – Tibby (2012)

Abstract: “An assessment of Australian climate during the Younger Dryas Chronozone (YDC) is presented. This review focuses on securely dated records from sites of continuous deposition, placing greatest emphasis on temperature reconstructions, with records of effective precipitation (i.e. the combined effect of precipitation minus evapotranspiration) also considered. While there is a paucity of Australian records covering the last glacial interglacial transition, particularly those which directly infer temperature, sufficient data exist to examine YDC climate from southern and eastern Australia. Temperature reconstructions from Tasmania, based on both chironomid and pollen data, show no evidence for Younger Dryas cooling. By contrast, there is evidence for cooling associated with the Antarctic Cold Reversal, from Tullabardine Dam pollen data and the sediment organic content from Eagle and Platypus Tarns in Tasmania. Records from a number of eastern Australian mainland sites provide no evidence of effective precipitation shifts concurrent with the Younger Dryas Chronozone. Similarly, reconstructions of discharge from the Murray-Darling Basin, which covers a large proportion (14%) of the Australian continent, and dust transport from a larger portion of the continent also show no evidence of climate shifts concomitant with the Younger Dryas. Of research published in the past decade, only one study, located in the Great Australian Bight, claims evidence of a YDC cooling (Andres et al., 2003). By contrast, this review suggests that there is no conclusive evidence for cooling, or indeed any distinctive climate patterning, during the Younger Dryas Chronozone in Australia.”

Citation: John Tibby, Quaternary International, doi:10.1016/j.quaint.2012.01.003.

When climate change emerges from the noise of natural variability?

Time of emergence of climate signals – Hawkins & Sutton (2012) [FULL TEXT]

Abstract: “The time at which the signal of climate change emerges from the noise of natural climate variability (Time of Emergence, ToE) is a key variable for climate predictions and risk assessments. Here we present a methodology for estimating ToE for individual climate models, and use it to make maps of ToE for surface air temperature (SAT) based on the CMIP3 global climate models. Consistent with previous studies we show that the median ToE occurs several decades sooner in low latitudes, particularly in boreal summer, than in mid-latitudes. We also show that the median ToE in the Arctic occurs sooner in boreal winter than in boreal summer. A key new aspect of our study is that we quantify the uncertainty in ToE that arises not only from inter-model differences in the magnitude of the climate change signal, but also from large differences in the simulation of natural climate variability. The uncertainty in ToE is at least 30 years in the regions examined, and as much as 60 years in some regions. Alternative emissions scenarios lead to changes in both the median ToE (by a decade or more) and its uncertainty. The SRES B1 scenario is associated with a very large uncertainty in ToE in some regions. Our findings have important implications for climate modelling and climate policy which we discuss.”

Citation: Hawkins, E. and R. Sutton (2012), Geophys. Res. Lett., 39, L01702, doi:10.1029/2011GL050087.

Westerlies describe North Atlantic Oscillation back to 1692

Estimates of the North Atlantic Oscillation back to 1692 using a Paris–London westerly index – Cornes et al. (2012)

Abstract: “A westerly index for Europe is developed back to 1692 using newly recovered and corrected Mean Sea-level Pressure (MSLP) data from London and Paris. The index is compared against various instrumental and proxy indices of the North Atlantic Oscillation (NAO). In the winter, the Paris-London index depicts a spatial pattern of atmospheric circulation that is bi-modal, with centres of action that are shifted eastwards compared to the NAO. Owing to asymmetry in the NAO the Paris-London index provides a good depiction of positive NAO conditions as well as extreme negative phases of the NAO that arise from reversals of the pressure centres, but less extreme negative NAO conditions are associated with westerly index values approaching zero. The merit in using the Paris-London index lies with its consistency over time as a measure of westerly wind flow, which may not be the case with other proxy-based indices. In the summer, the Paris-London index bears a close relationship to the reconstructed high-summer NAO series of Folland et al. (2009) as well as the summer Luterbacher et al. (1999) NAO reconstruction. An important finding is that the summer NAO was highly variable during the early nineteenth century but was predominately positive on the decadal time scale during that period. Since circa 1970 the summer index has mostly been negative, indicating reduced westerlies and increased blocking conditions that are exceptional in the context of the last 250 years.”

Citation: Richard C. Cornes, Philip D. Jones, Keith R. Briffa, Timothy J. Osborn, International Journal of Climatology, DOI: 10.1002/joc.3416.

New article says cosmic rays have strong effect to climate

Cosmic rays and space weather: effects on global climate change – Dorman (2012) [FULL TEXT]

Comments: This paper makes a case for strong effect of cosmic rays on climate. However, the paper seems to ignore most of the papers showing evidence against the cosmic ray hypothesis. There are plenty of such papers. Discussion section mentions couple of them in passing but otherwise they are ignored. Paper also seems to use very old data, as is evident for example in Figures 2, 3, and 4, but newer data is not touched.

Abstract: “We consider possible effects of cosmic rays and some other space factors on the Earth’s climate change. It is well known that the system of internal and external factors formatting the climate is very unstable; decreasing planetary temperature leads to an increase of snow surface, and decrease of the total solar energy input into the system decreases the planetary temperature even more, etc. From this it follows that even energetically small factors may have a big influence on climate change. In our opinion, the most important of these factors are cosmic rays and cosmic dust through their influence on clouds, and thus, on climate.”

Citation: Dorman, L. I., Ann. Geophys., 30, 9-19, doi:10.5194/angeo-30-9-2012, 2012.

Different malaria species react differently to warming in India’s Thar Desert

Influence of climate on incidences of malaria in the Thar Desert, northwest India – Jhajharia et al. (2012)

Abstract: “Climatic variability and rise in temperature are considered as the key determinants to the transmission of malaria. In the present study, the trends in the cases of malaria caused by Plasmodium falciparum and Plasmodium vivax were investigated by using the nonparametric Mann-Kendall test after removing the effect of significant lag-1 serial correlation from the time series of cases of malaria incidence by pre-whitening in annual, seasonal, and monthly time scales at Bikaner, located in the Thar Desert of Rajasthan, in northwest India. Multi-collinearity within the datasets under consideration was investigated by means of correlation matrix, the Bartlett sphericity test, and the Kaiser-Meyer-Olkin measure of sampling adequacy, subsequent to which it was removed by using principal component analysis. Finally, artificial neural network models were employed to predict cases of malaria incidence caused by P. falciparum and P. vivax at various scales. During the last 34 years from 1975 to 2008, P. falciparum malaria incidence cases have been found to increase significantly corresponding to monthly (April and September) and seasonal (monsoon) time scales over Bikaner. On the other hand, no significant trends were observed in P. vivax malaria cases at Bikaner. Concomitant increases in P. falciparum cases of malaria incidence and observed temperature increases at Bikaner hint that P. falciparum malaria may have grown significantly under the warming climate of the Thar Desert.”

Citation: Deepak Jhajharia, Surajit Chattopadhyay, Rahul R. Choudhary, Vas Dev, Vijay P. Singh, Shankar Lal, International Journal of Climatology, DOI: 10.1002/joc.3424.

Review article on East Siberian Arctic Shelf carbon transport

On carbon transport and fate in the East Siberian Arctic land–shelf–atmosphere system – Semiletov et al. (2012) [FULL TEXT]

Abstract: ”This review paper summarizes current understanding of the transport of organic carbon to, and the fate of organic carbon within, the East Siberian Arctic Shelf (ESAS), and of processes determining carbon dioxide (CO₂) and methane (CH₄) fluxes from the ESAS to the atmosphere achieved from analyzing the data sets obtained on 20 expeditions performed from 1999 to 2011. This study of the ESAS was aimed at investigating how redistribution of old carbon from degrading terrestrial and sub-sea permafrost and from coastal erosion contributes to the carbon pool of the ESAS, how changes in the hydrological cycle of the surrounding land and alteration of terrestrial carbon cycles affect the hydrological and biogeochemical parameters of shelf water masses, and which factors control CH₄ and CO₂ emissions from the ESAS. This report describes selected results achieved by a developing international scientific partnership that has been crucial at every stage of the study and will be even more important in the future.”

Citation: Igor P Semiletov et al 2012 Environ. Res. Lett. 7 015201 doi:10.1088/1748-9326/7/1/015201.

Female corals are more vulnerable to elevated carbon dioxide

An investigation of the calcification response of the scleractinian coral Astrangia poculata to elevated pCO2 and the effects of nutrients, zooxanthellae and gender – Holcomb et al. (2012) [FULL TEXT]

Abstract: “The effects of nutrients and pCO₂ on zooxanthellate and azooxanthellate colonies of the temperate scleractinian coral Astrangia poculata (Ellis and Solander, 1786) were investigated at two different temperatures (16 °C and 24 °C). Corals exposed to elevated pCO₂ tended to have lower relative calcification rates, as estimated from changes in buoyant weights. Experimental nutrient enrichments had no significant effect nor did there appear to be any interaction between pCO₂ and nutrients. Elevated pCO₂ appeared to have a similar effect on coral calcification whether zooxanthellae were present or absent at 16 °C. However, at 24 °C, the interpretation of the results is complicated by a significant interaction between gender and pCO₂ for spawning corals. At 16 °C, gamete release was not observed, and no gender differences in calcification rates were observed – female and male corals showed similar reductions in calcification rates in response to elevated CO₂ (15% and 19% respectively). Corals grown at 24 °C spawned repeatedly and male and female corals exhibited two different growth rate patterns – female corals grown at 24 °C and exposed to CO₂ had calcification rates 39% lower than females grown at ambient CO₂, while males showed a non-significant decline of 5% under elevated CO₂. The increased sensitivity of females to elevated pCO₂ may reflect a greater investment of energy in reproduction (egg production) relative to males (sperm production). These results suggest that both gender and spawning are important factors in determining the sensitivity of corals to ocean acidification, and considering these factors in future research may be critical to predicting how the population structures of marine calcifiers will change in response to ocean acidification.”

Citation: Holcomb, M., Cohen, A. L., and McCorkle, D. C., Biogeosciences, 9, 29-39, doi:10.5194/bg-9-29-2012, 2012.

Inland waters take in organic carbon and emit methane

Extreme organic carbon burial fuels intense methane bubbling in a temperate reservoir – Sobek et al. (2012)

Abstract: “Organic carbon (OC) burial and greenhouse gas emission of inland waters plays an increasingly evident role in the carbon balance of the continents, and particularly young reservoirs in the tropics emit methane (CH₄) at high rates. Here we show that an old, temperate reservoir acts simultaneously as a strong OC sink and CH₄ source, because the high sedimentation rate supplies reactive organic matter to deep, anoxic sediment strata, fuelling methanogenesis and gas bubble emission (ebullition) of CH₄ from the sediment. Damming of the river has resulted in the build-up of highly methanogenic sediments under a shallow water column, facilitating the transformation of fixed CO₂ to atmospheric CH₄. Similar high OC burial and CH₄ ebullition is expected in other reservoirs and natural river deltas.”

Citation: Sobek, S., T. DelSontro, N. Wongfun, and B. Wehrli (2012), Geophys. Res. Lett., 39, L01401, doi:10.1029/2011GL050144.

Small net positive radiative forcing of dark aerosols above bright clouds

Direct and semi-direct radiative forcing of smoke aerosols over clouds – Wilcox (2012) [FULL TEXT]

Abstract: “Observations from Earth observing satellites indicate that dark carbonaceous aerosols that absorb solar radiation are widespread in the tropics and subtropics. When these aerosols mix with clouds, there is generally a reduction of cloudiness owing to absorption of solar energy in the aerosol layer. Over the subtropical South Atlantic Ocean, where smoke from savannah burning in southern Africa resides above a persistent deck of marine stratocumulus clouds, radiative heating of the smoke layer leads to a thickening of the cloud layer. Here, satellite observations of the albedo of overcast scenes of 25 km² size or larger are combined with additional satellite observations of clouds and aerosols to estimate the top-of-atmosphere direct radiative forcing attributable to presence of dark aerosol above bright cloud, and the negative semi-direct forcing attributable to the thickening of the cloud layer. The average positive direct radiative forcing by smoke over an overcast scene is 9.2±6.6 W m⁻² for cases with an unambiguous signal of absorbing aerosol over cloud in passive ultraviolet remote sensing observations. However, cloud liquid water path is enhanced by 16.3±7.7 g m⁻² across the range of values for sea surface temperature for cases of smoke over cloud. The negative radiative forcing associated with this semi-direct effect of smoke over clouds is estimated to be −5.9±3.5 W m⁻². Therefore, the cooling associated with the semi-direct cloud thickening effect compensates for greater than 60 % of the direct radiative effect. Accounting for the frequency of occurrence of significant absorbing aerosol above overcast scenes leads to an estimate of the average direct forcing of 1.0±0.7 W m⁻² contributed by these scenes averaged over the subtropical southeast Atlantic Ocean during austral winter. The regional average of the negative semi-direct forcing is −0.7±0.4 W m⁻². Therefore, smoke aerosols overlaying the decks of overcast marine stratocumulus clouds considered here yield a small net positive radiative forcing, which results from the difference of two larger effects.”

Citation: Wilcox, E. M., Atmos. Chem. Phys., 12, 139-149, doi:10.5194/acp-12-139-2012, 2012.

CLASSIC OF THE WEEK: Schneider (1972)

Cloudiness as a Global Climatic Feedback Mechanism: The Effects on the Radiation Balance and Surface Temperature of Variations in Cloudiness – Schneider (1972) [FULL TEXT]

Abstract: “The effect of variation in cloudiness on the climate is considered in terms of 1) a relation between the radiation balance of the earth-atmosphere system and variations in the amount of cloud cover or effective cloud top height, 2) the effect on the surface temperature of variations in cloudiness, and 3) the dynamic coupling or “feedback” effects relating changes in surface temperature to the formation of clouds. The first two points are studied by numerical integration of a simple radiation flux model, and the third point is discussed qualitatively. Global-average radiation balance calculations show that an increase in the amount of low and middle level cloud cover (with cloud top height and cloud albedo fixed) decreases the surface temperature. But, this result for the global-average case does not hold near polar regions, where the albedo of the cloudy areas can he comparable to (or even smaller than) the albedo of the snow-covered cloudless areas, and where, especially in the winter season, the amount of incoming solar radiation at high latitudes is much less than the global-average value of insolation. The exact latitude at which surface cooling changes to surface warming from a given increase in cloud cover amount depends critically upon the local values of the cloud albedo and the albedo of the cloudless areas that are used in the calculation. However, an increase in effective cloud top height (with cloud cover and cloud albedo fixed) increases the surface temperature at all latitudes.”

Citation: Schneider, Stephen H., 1972, J. Atmos. Sci., 29, 1413–1422, doi: http://dx.doi.org/10.1175/1520-0469(1972)0292.0.CO;2.

Multiyear ice turning to seasonal ice in Arctic Ocean

On the Arctic Ocean ice thickness response to changes in the external forcing – Stranne & Björk (2011) “Submarine and satellite observations show that the Arctic Ocean ice cover has undergone a large thickness reduction and a decrease in the areal extent during the last decades. Here the response of the Arctic Ocean ice cover to changes in the poleward atmospheric energy transport, F wall, is investigated using coupled atmosphere-ice-ocean column models. Two models with highly different complexity are used in order to illustrate the importance of different internal processes and the results highlight the dramatic effects of the negative ice thickness—ice volume export feedback and the positive surface albedo feedback. The steady state ice thickness as a function of F wall is determined for various model setups and defines what we call ice thickness response curves. When a variable surface albedo and snow precipitation is included, a complex response curve appears with two distinct regimes: a perennial ice cover regime with a fairly linear response and a less responsive seasonal ice cover regime. The two regimes are separated by a steep transition associated with surface albedo feedback. The associated hysteresis is however small, indicating that the Arctic climate system does not have an irreversible tipping point behaviour related to the surface albedo feedback. The results are discussed in the context of the recent reduction of the Arctic sea ice cover. A new mechanism related to regional and temporal variations of the ice divergence within the Arctic Ocean is presented as an explanation for the observed regional variation of the ice thickness reduction. Our results further suggest that the recent reduction in areal ice extent and loss of multiyear ice is related to the albedo dependent transition between seasonal and perennial ice i.e. large areas of the Arctic Ocean that has previously been dominated by multiyear ice might have been pushed below a critical mean ice thickness, corresponding to the above mentioned transition, and into a state dominated by seasonal ice.” Christian Stranne and Göran Björk, Climate Dynamics, DOI: 10.1007/s00382-011-1275-y.

Cold Arctic winters might come with ozone holes

Arctic winter 2010/2011 at the brink of an ozone hole – Sinnhuber et al. (2011) “The Arctic stratospheric winter of 2010/2011 was one of the coldest on record with a large loss of stratospheric ozone. Observations of temperature, ozone, nitric acid, water vapor, nitrous oxide, chlorine nitrate and chlorine monoxide from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT are compared to calculations with a chemical transport model (CTM). There is overall excellent agreement between the model calculations and MIPAS observations, indicating that the processes of denitrification, chlorine activation and catalytic ozone depletion are sufficiently well represented. Polar vortex integrated ozone loss reaches 120 Dobson Units (DU) by early April 2011. Sensitivity calculations with the CTM give an additional ozone loss of about 25 DU at the end of the winter for a further cooling of the stratosphere by 1 K, showing locally near-complete ozone depletion (remaining ozone <200 ppbv) over a large vertical extent from 16 to 19 km altitude. In the CTM a 1 K cooling approximately counteracts a 10% reduction in stratospheric halogen loading, a halogen reduction that is expected to occur in about 13 years from now. These results indicate that severe ozone depletion like in 2010/2011 or even worse could appear for cold Arctic winters over the next decades if the observed tendency for cold Arctic winters to become colder continues into the future." Sinnhuber, B.-M., G. Stiller, R. Ruhnke, T. von Clarmann, S. Kellmann, and J. Aschmann (2011), Geophys. Res. Lett., 38, L24814, doi:10.1029/2011GL049784.

Some clouds go undetected by some cloud-detecting satellites

Cloud features detected by MODIS but not by CloudSat and CALIOP – Chan & Comiso (2011) “The ability to characterize the global cloud cover from space has been greatly enhanced by the availability of MODIS, CloudSat, and CALIOP data. The three sensors provide good complementary information about clouds. In this study, we investigated unexpected observations of certain types of clouds apparent in the MODIS data but not detected by CloudSat and CALIOP. Several examples are presented and generally these undetected clouds are geometrically thin, low-level clouds. In particular, they are located in the Arctic region and have optical thicknesses of less than 14, top height altitudes of below 2.5 km, and layer thickness of less than 1 km. CloudSat may miss such low-level clouds because of its coarse vertical resolution of about 500 m and it has limited sensitivity near the surface. Unexpectedly, CALIOP with a much higher vertical resolution of 30 m also misses these clouds and this is due to the cloud’s geometrically thin nature and surface proximity.” Chan, M. A. and J. C. Comiso (2011), Geophys. Res. Lett., 38, L24813, doi:10.1029/2011GL050063.

Global warming is projected to increase hydroclimate variability

Does global warming cause intensified interannual hydroclimate variability? – Seager et al. (2011) “The idea that global warming leads to more droughts and floods has become commonplace without clear indication of what is meant by this statement. Here we examine one aspect of this problem and assess whether interannual variability of precipitation (P) minus evaporation (E) becomes stronger in the 21st Century compared to the 20th Century, as deduced from an ensemble of models participating in Coupled Model Intercomparison Project 3. It is shown that indeed interannual variability of P-E does increase almost everywhere across the planet with a few notable exceptions such as southwestern North America and some subtropical regions. The variability increases most at the Equator and the high latitudes and least in the subtropics. While most interannual P-E variability arises from internal atmosphere variability the primary potentially predictable component is related to the El Niño-Southern Oscillation (ENSO). ENSO-driven interannual P-E variability clearly increases in amplitude in the tropical Pacific but elsewhere the changes are more complex. This is not surprising in that ENSO-driven P-E anomalies are primarily caused by circulation anomalies combining with the climatological humidity field. As climate warms and the specific humidity increases this term leads to an intensification of ENSO-driven P-E variability. However, ENSO-driven circulation anomalies also change, in some regions amplifying, but in others opposing and even overwhelming, the impact of rising specific humidity. Consequently there is sound scientific basis for anticipating a general increase in interannual P-E variability but the predictable component will depend in a more complex way on both thermodynamic responses to global warming and on how tropically-forced circulation anomalies alter.” Richard Seager, Naomi Naik, Laura Vogel, Journal of Climate, doi: http://dx.doi.org/10.1175/JCLI-D-11-00363.1. [Full text]

No evidence for robust link between cloud cover and solar activity/cosmic rays

Solar irradiance, cosmic rays and cloudiness over daily timescales – Laken & Čalogović (2011) “Although over centennial and greater timescales solar variability may be one of the most influential climate forcing agents, the extent to which solar activity influences climate over shorter time periods is poorly understood. If a link exists between solar activity and climate, it is likely via a mechanism connected to one (or a combination) of the following parameters: total solar irradiance (TSI), ultraviolet (UV) spectral irradiance, or the galactic cosmic ray (GCR) flux. We present an analysis based around a superposed epoch (composite) approach focusing on the largest TSI increases and decreases (the latter occurring in both the presence and absence of appreciable GCR reductions) over daily timescales. Using these composites we test for the presence of a robust link between solar activity and cloud cover over large areas of the globe using rigorous statistical techniques. We find no evidence that widespread variations in cloud cover at any tropospheric level are significantly associated with changes in the TSI, GCR or UV flux, and further conclude that TSI or UV changes occurring during reductions in the GCR flux are not masking a solar-cloud response. However, we note the detectability of any potential links is strongly constrained by cloud variability.” Laken, B. A. and J. Čalogović(2011), Geophys. Res. Lett., 38, L24811, doi:10.1029/2011GL049764.

Hypoxic and anoxic areas will very likely increase in Baltic Sea with warming climate

Hypoxia in future climates: A model ensemble study for the Baltic Sea – Meier et al. (2011) “Using an ensemble of coupled physical-biogeochemical models driven with regionalized data from global climate simulations we are able to quantify the influence of changing climate upon oxygen conditions in one of the numerous coastal seas (the Baltic Sea) that suffers worldwide from eutrophication and from expanding hypoxic zones. Applying various nutrient load scenarios we show that under the impact of warming climate hypoxic and anoxic areas will very likely increase or at best only slightly decrease (in case of optimistic nutrient load reductions) compared to present conditions, regardless of the used global model and climate scenario. The projected decreased oxygen concentrations are caused by (1) enlarged nutrient loads due to increased runoff, (2) reduced oxygen flux from the atmosphere to the ocean due to increased temperature, and (3) intensified internal nutrient cycling. In future climate a similar expansion of hypoxia as projected for the Baltic Sea can be expected also for other coastal oceans worldwide.” Meier, H. E. M., H. C. Andersson, K. Eilola, B. G. Gustafsson, I. Kuznetsov, B. Müller-Karulis, T. Neumann, and O. P. Savchuk (2011), Geophys. Res. Lett., 38, L24608, doi:10.1029/2011GL049929.

Global monsoon precipitation has intensified

Recent change of the global monsoon precipitation (1979–2008) – Wang et al. (2011) “The global monsoon (GM) is a defining feature of the annual variation of Earth’s climate system. Quantifying and understanding the present-day monsoon precipitation change are crucial for prediction of its future and reflection of its past. Here we show that regional monsoons are coordinated not only by external solar forcing but also by internal feedback processes such as El Niño-Southern Oscillation (ENSO). From one monsoon year (May to the next April) to the next, most continental monsoon regions, separated by vast areas of arid trade winds and deserts, vary in a cohesive manner driven by ENSO. The ENSO has tighter regulation on the northern hemisphere summer monsoon (NHSM) than on the southern hemisphere summer monsoon (SHSM). More notably, the GM precipitation (GMP) has intensified over the past three decades mainly due to the significant upward trend in NHSM. The intensification of the GMP originates primarily from an enhanced east–west thermal contrast in the Pacific Ocean, which is coupled with a rising pressure in the subtropical eastern Pacific and decreasing pressure over the Indo-Pacific warm pool. While this mechanism tends to amplify both the NHSM and SHSM, the stronger (weaker) warming trend in the NH (SH) creates a hemispheric thermal contrast, which favors intensification of the NHSM but weakens the SHSM. The enhanced Pacific zonal thermal contrast is largely a result of natural variability, whilst the enhanced hemispherical thermal contrast is likely due to anthropogenic forcing. We found that the enhanced global summer monsoon not only amplifies the annual cycle of tropical climate but also promotes directly a “wet-gets-wetter” trend pattern and indirectly a “dry-gets-drier” trend pattern through coupling with deserts and trade winds. The mechanisms recognized in this study suggest a way forward for understanding past and future changes of the GM in terms of its driven mechanisms.” Bin Wang, Jian Liu, Hyung-Jin Kim, Peter J. Webster and So-Young Yim, Climate Dynamics, DOI: 10.1007/s00382-011-1266-z. [Full text]

Greenland glacier has 3 positive melt feedbacks active

Three positive feedback mechanisms for ice-sheet melting in a warming climate – Ren & Leslie (2011) “Three positive feedback mechanisms that accelerate ice-sheet melting are assessed in a warming climate, using a numerical ice model driven by atmospheric climate models. The Greenland ice sheet (GrIS) is the modeling test-bed under accelerated melting conditions. The first feedback is the interaction of sea water with ice. It is positive because fresh water melts ice faster than salty water, owing primarily to the reduction in water heat capacity by solutes. It is shown to be limited for the GrIS, which has only a small ocean interface, and the grounding line of some fast glaciers becomes land-terminating during the 21st century. The second positive feedback, strain heating, is positive because it produces further ice heating inside the ice sheet. The third positive feedback, granular basal sliding, applies to all ice sheets and becomes the dominant feedback during the 21st century. A numerical simulation of Jakobshavn Isbrae over the 21st century reveals that all three feedback processes are active for this glacier. Compared with the year 2000 level, annual ice discharge into the ocean could increase by ∼1.4 km³ a^-1 (∼5% of the present annual rate) by 2100. Granular basal sliding contributes ∼40% of this increase.” Ren, Diandong; Leslie, Lance M., Journal of Glaciology, Volume 57, Number 206, December 2011 , pp. 1057-1066(10), DOI: http://dx.doi.org/10.3189/002214311798843250.

Tree ring based winter temperature reconstruction from China

Tree ring-based winter temperature reconstruction for Changting, Fujian, subtropical region of Southeast China, since 1850: linkages to the Pacific Ocean – Chen et al. (2011) “Until recently, there have been very few tree-ring studies in southeast China due largely to the scarcity of old trees and the complexity of relationships between tree growth and climate in subtropical regions of China. Recent studies on the conifers in southeast China revealed that tree ring-based climate reconstructions are feasible. Here, we describe a reconstruction (AD 1850–2009) of November–February maximum temperatures for Changting, Fujian, southeast China based on tree ring width data of Pinus massiniana which considerably extends the available climatic information. Calibration and verification statistics for the period 1956–2009 show a high level of skill and account for a significant portion of the observed variance (32.9%) irrespective of which period is used to develop or verify the regression model. Split sample validation supports our use of a reconstruction model based on the full period of reliable observational data (1956–2009). Warm periods occurred during 1854–1859, 1868–1880, 1885–1899, 1906–1914, 1920–1943, 1964–1975 and 1994–present; while the periods of AD 1850–1853, 1860–1867, 1881–1884, 1900–1907, 1915–1919, 1944–1963 and 1976–1993 were relatively cold. The climate correlation analyses with gridded temperature dataset and SST revealed that our season temperature reconstruction contains the strong large-scale climate signals. Our results suggest that some warm winters of Changting are coincident with El Niño events over the past 150 years. In addition, several severely cold winters coincide with major volcanic eruptions.” Feng Chen, Yu-jiang Yuan, Wen-shou Wei, Shu-long Yu and Tong-wen Zhang, Theoretical and Applied Climatology, DOI: 10.1007/s00704-011-0563-0.

Reduced vertical mixing might cause Arctic amplification

Boundary layer stability and Arctic climate change: a feedback study using EC-Earth – Bintanja et al. (2011)“Amplified Arctic warming is one of the key features of climate change. It is evident in observations as well as in climate model simulations. Usually referred to as Arctic amplification, it is generally recognized that the surface albedo feedback governs the response. However, a number of feedback mechanisms play a role in AA, of which those related to the prevalent near-surface inversion have received relatively little attention. Here we investigate the role of the near-surface thermal inversion, which is caused by radiative surface cooling in autumn and winter, on Arctic warming. We employ idealized climate change experiments using the climate model EC-Earth together with ERA-Interim reanalysis data to show that boundary-layer mixing governs the efficiency by which the surface warming signal is ‘diluted’ to higher levels. Reduced vertical mixing, as in the stably stratified inversion layer in Arctic winter, thus amplifies surface warming. Modelling results suggest that both shortwave—through the (seasonal) interaction with the sea ice feedback—and longwave feedbacks are affected by boundary-layer mixing, both in the Arctic and globally, with the effect on the shortwave feedback dominating. The amplifying effect will decrease, however, with climate warming because the surface inversion becomes progressively weaker. We estimate that the reduced Arctic inversion has slowed down global warming by about 5% over the past 2 decades, and we anticipate that it will continue to do so with ongoing Arctic warming.” R. Bintanja, E. C. van der Linden and W. Hazeleger, Climate Dynamics, DOI: 10.1007/s00382-011-1272-1.

Physical characterization of aerosol particles during the Chinese New Year’s firework events – Zhang et al. (2010) “Measurements for particles 10 nm to 10 μm were taken using a Wide-range Particle Spectrometer during the Chinese New Year (CNY) celebrations in 2009 in Shanghai, China. These celebrations provided an opportunity to study the number concentration and size distribution of particles in an especial atmospheric pollution situation due to firework displays. The firework activities had a clear contribution to the number concentration of small accumulation mode particles (100–500 nm) and PM₁ mass concentration, with a maximum total number concentration of 3.8 × 10⁴ cm⁻³. A clear shift of particles from nucleation and Aitken mode to small accumulation mode was observed at the peak of the CNY firework event, which can be explained by reduced atmospheric lifetimes of smaller particles via the concept of the coagulation sink. High particle density (2.7 g cm⁻³) was identified as being particularly characteristic of the firework aerosols. Recalculated fine particles PM₁ exhibited on average above 150 μg m⁻³ for more than 12 hours, which was a health risk to susceptible individuals. Integral physical parameters of firework aerosols were calculated for understanding their physical properties and further model simulation.” Min Zhang, Xuemei Wang, Jianmin Chen, Tiantao Cheng, Tao Wang, Xin Yang, Youguo Gong, Fuhai Geng, Changhong Chen, Atmospheric Environment, Volume 44, Issue 39, December 2010, Pages 5191-5198, doi:10.1016/j.atmosenv.2010.08.048. [Full text]

Effect of fireworks events on urban background trace metal aerosol concentrations: Is the cocktail worth the show? – Moreno et al. (2010) “We report on the effect of a major firework event on urban background atmospheric PM_2.5 chemistry, using 24-h data collected over 8 weeks at two sites in Girona, Spain. The firework pollution episode (Sant Joan fiesta on 23rd June 2008) measured in city centre parkland increased local background PM_2.5 concentrations as follows: Sr (x86), K (x26), Ba (x11), Co (x9), Pb (x7), Cu (x5), Zn (x4), Bi (x4), Mg (x4), Rb (x4), Sb (x3), P (x3), Ga (x2), Mn (x2), As (x2), Ti (x2) and SO₄²⁻ (x2). Marked increases in these elements were also measured outside the park as the pollution cloud drifted over the city centre, and levels of some metals remained elevated above background for days after the event as a reservoir of metalliferous dust persisted within the urban area. Transient high-PM pollution episodes are a proven health hazard, made worse in the case of firework combustion because many of the elements released are both toxic and finely respirable, and because displays commonly take place in an already polluted urban atmosphere.” Teresa Moreno, Xavier Querol, Andrés Alastuey, Fulvio Amato, Jorge Pey, Marco Pandolfi, Nino Kuenzli, Laura Bouso, Marcela Rivera, Wes Gibbons, Journal of Hazardous Materials, Volume 183, Issues 1-3, 15 November 2010, Pages 945-949, doi:10.1016/j.jhazmat.2010.07.082.

Effect of fireworks display on perchlorate in air aerosols during the Spring Festival – Shi et al. (2010) “Perchlorate is regarded as a new emerging persistent inorganic environmental contaminant. It can result in important neurodevelopmental deficits and goiter in infants and children because of its inhibition of iodine uptake into the thyroid tissue. Furthermore, its presence in the human body can cause improper regulation of metabolism for adults. It is often used as ingredient in the production of fireworks. So fireworks display may influence the perchlorate levels in atmospheric particulate matter (PM). In this paper perchlorate was determined in air aerosol samples (Inhalable particulate matter (PM10) and larger particulate matter (PM10-100)) collected from two locations (Lanzhou City and Yuzhong County) in Gansu province over a month period (February 1rst to March 4th) during the Spring Festival (February 18th) in 2007 in order to study the effect of fireworks display on perchlorate in air aerosol. The results showed that different concentrations of perchlorate were detected in almost all samples, ranging from <detection limit value to 39.16 ng m⁻³. And the detection frequencies of perchlorate were 91% (100%) and 50% (59%) for PM10-100 (PM10) in Lanzhou City and Yuzhong County, respectively. The highest concentrations were all found in the samples from two sites on New Year’s Eve, which was 39.16 ng m⁻³ (PM10-100) and 9.89 ng m⁻³ (PM10) for Lanzhou city, 3.43 ng m⁻³ (PM10-100) and 4.97 ng m⁻³ (PM10) for Yuzhong County, 6.8-26.2 times as the mean concentrations during the period of no or limited fireworks display. This indicated that the fireworks display during the Spring Festival can result in the levels of perchlorate increase.” Yali Shi, Ning Zhang, Jianmin Gao, Xin Li, Yaqi Cai, Atmospheric Environment, Volume 45, Issue 6, February 2011, Pages 1323-1327, doi:10.1016/j.atmosenv.2010.11.056.

Heavy metals from pyrotechnics in New Years Eve snow – Steinhauser et al. (2008) “Pyrotechnics and fireworks cause pollution with barium aerosols, which is a result of the utilization of barium nitrate as a combined pyrotechnic oxidizer and coloring agent. In this study, the washing-out of barium-rich aerosols by snowflakes during the New Years Eve celebrations in an Austrian village in the Alps has been investigated. It could be shown that the fireworks caused an increase in the barium concentration in snow of up to a factor of 580 compared to the blank value. An increase of the concentrations of strontium and occasionally arsenic in snow was also observed. The geographic distribution of the pyrotechnic combustion products on this snowy evening was restricted to a relatively small area and even in a very local scale, the variations in the concentrations were remarkable. Post-firework snow from the summits of nearby located mountains was found to be as clean as pre-firework snow. However, snow that was visibly contaminated with smoke residues contained exorbitant concentrations of Ba, K, Sr, and Fe.” Georg Steinhauser, Johannes H. Sterba, Michaela Foster, Friedrich Grass, Max Bichler, Atmospheric Environment, Volume 42, Issue 37, December 2008, Pages 8616-8622, doi:10.1016/j.atmosenv.2008.08.023.

The impact of fireworks on airborne particles – Vecchi et al. (2008) ”Fireworks are one of the most unusual sources of pollution in atmosphere; although transient, these pollution episodes are responsible for high concentrations of particles (especially metals and organic compounds) and gases. In this paper, results of a study on chemical–physical properties of airborne particles (elements, ions, organic and elemental carbon and particles size distributions) collected during a fireworks episode in Milan (Italy) are reported. Elements typically emitted during pyrotechnic displays increased in 1 h as follows: Sr (120 times), Mg (22 times), Ba (12 times), K (11 times), and Cu (6 times). In our case study, Sr was recognised as the best fireworks tracer because its concentration was very high during the event and lower than, or comparable with, minimum detection limits during other time intervals, suggesting that it was mainly due to pyrotechnic displays. In addition, particles number concentrations increased significantly during the episode (up to 6.7 times in 1 h for the 0.5<d<1 μm size bin). Contributions (e.g. Cu, elemental carbon and nitrogen oxides) to air pollution due to the large traffic volume registered during the same night were also singled out. The original application of Positive Matrix Factorisation and Multiple Linear Regression allowed, as far as we know, here for the first time, the quantification of the fireworks contribution to atmospheric particulate matter (PM) and the resolution of their chemical profile. The contribution of fireworks to the local environment in terms of PM₁₀ mass, elements and chemical components was assessed with 4-h time resolution. PM₁₀ mass apportioned by fireworks was up to 33.6 μg m⁻³ (about 50% of the total PM₁₀ mass). Major contributors were elemental and organic carbon (2.8 and 8.1 μg m⁻³, respectively) as well as metals like Mg, K, Sr, Ba, and Cu (0.4, 0.7, 0.07, 0.1, and 0.1 μg m⁻³, respectively).” Roberta Vecchi, Vera Bernardoni, Diana Cricchio, Alessandra D’Alessandro, Paola Fermo, Franco Lucarelli, Silvia Nava, Andrea Piazzalunga, Gianluigi Valli, Atmospheric Environment, Volume 42, Issue 6, February 2008, Pages 1121-1132, doi:10.1016/j.atmosenv.2007.10.047.

Ambient air quality of Lucknow City (India) during use of fireworks on Diwali Festival – Barman et al. (2008) “The present study deals with the effect of fireworks on ambient air quality during Diwali Festival in Lucknow City. In this study, PM₁₀, SO₂, NO _x and 10 trace metals associated with PM₁₀ were estimated at four representative locations, during day and night times for Pre Diwali (day before Diwali) and Diwali day. On Diwali day 24 h average concentration of PM₁₀, SO₂, and NO _x was found to be 753.3, 139.1, and 107.3 μg m⁻³, respectively, and these concentrations were found to be higher at 2.49 and 5.67 times for PM₁₀, 1.95 and 6.59 times for SO₂ and 1.79 and 2.69 for NO _x , when compared with the respective concentration of Pre Diwali and normal day, respectively. On Diwali day, 24 h values for PM₁₀, SO₂, and NO _x were found to be higher than prescribed limit of National Ambient Air Quality Standard (NAAQS), and exceptionally high (7.53 times) for PM₁₀. On Diwali night (12 h) mean level of PM₁₀, SO₂ and NO _x was 1,206.2, 205.4 and 149.0 μg m⁻³, respectively, which was 4.02, 2.82 and 2.27 times higher than their respective daytime concentrations and showed strong correlations (p<0.01) with each other. The 24 h mean concentration of metals associated with PM₁₀ was found to be in the order of Ca (3,169.44)>Fe (747.23)>Zn (542.62)>Cu (454.03),>Pb (307.54)>Mn (83.90)>Co (78.69)>Cr (42.10)>Ni (41.47)>Cd (34.69) in ng m⁻³ and all these values were found to be higher than the Pre Diwali (except Fe) and normal day. The metal concentrations on Diwali day were found to be significantly different than normal day (except Fe & Cu). The concentrations of Co, Ni, Cr and Cd on Diwali night were found to be significantly higher than daytime concentrations for Pre Diwali (control). The inter correlation of metals between Ca with Pb, Zn with Ni and Cr, Cu with Co, Co with Mn, Ni with Cd, Mn with Cd, Ni with Cd and Cr, and Cr with Cd showed significant relation either at p<0.05 or P<0.01 levels, which indicated that their sources were the same. The metals Cu, Co, Ni, Cr and Cd showed significant (p<0.01) association with PM₁₀. These results indicate that fireworks during Diwali festival affected the ambient air quality adversely due to emission and accumulation of PM₁₀, SO₂, NO _x and trace metals.” S. C. Barman, Ramesh Singh, M. P. S. Negi and S. K. Bhargava, Environmental Monitoring and Assessment, Volume 137, Numbers 1-3, 495-504, DOI: 10.1007/s10661-007-9784-1.

Recreational atmospheric pollution episodes: Inhalable metalliferous particles from firework displays – Moreno et al. (2007) ”The use of fireworks creates an unusual and distinctive anthropogenic atmospheric pollution event. We report on aerosol samples collected during Las Fallas in Valencia, a 6-day celebration famous for its firework displays, and add comparative data on firework- and bonfire-contaminated atmospheric aerosol samples collected from elsewhere in Spain (Barcelona, L’Alcora, and Borriana) and during the Guy Fawkes celebrations in London. Specific high-profile official firework events during Las Fallas included the afternoon Mascletà and the nightly aerial displays (especially in the climactic final 2 days of the fiesta) and were accompanied by pollution spikes in suspended particles, NO, SO2, and the creation and dispersal of an aerosol cloud enriched in a range of metallic elements. Notable metal aerosol concentration increases recorded during Las Fallas were potassium (from 500 to 5900 ng m−3), aluminium (as Al2O3 from around 600 to 2200 ng m−3), titanium (from 200 to 700 ng m−3), magnesium (from 100 to 500 ng m−3), lead (from 17 to 379 ng m−3), barium (from 39 to 322 ng m−3), strontium (from 3 to 112 ng m−3), copper (from 12 to 71 ng m−3), and antimony (from 1 to 52 ng m−3). Firework-contaminated aerosols of similarly metalliferous composition were also identified at the other monitoring sites, although different sites show variations attributable to other sources such as bonfires and local industry. Unusual levels of the trace elements Ba, Sr and (to a lesser extent) Cu, always in proportions with Ba dominant, along with strongly enhanced K, Pb, and Sb, are identified as being particularly characteristic of firework aerosols. Although firework-related recreational pollution episodes are transient in nature, they are highly concentrated, contribute significantly to total annual metal emissions, and are on average fine enough to be easily inhaled and a health risk to susceptible individuals.” Teresa Moreno, Xavier Querol, Andrés Alastuey, Mari Cruz Minguillón, b, Jorge Pey, Sergio Rodriguez, José Vicente Miró, Carles Felis, Wes Gibbons, Atmospheric Environment, Volume 41, Issue 5, February 2007, Pages 913-922, doi:10.1016/j.atmosenv.2006.09.019.

The air pollution caused by the burning of fireworks during the lantern festival in Beijing – Wang et al. (2007) “The effects of the burning of fireworks on air quality in Beijing was firstly assessed from the ambient concentrations of various air pollutants (SO₂, NO₂, PM_2.5, PM₁₀ and chemical components in the particles) during the lantern festival in 2006. Eighteen ions, 20 elements, and black carbon were measured in PM_2.5 and PM₁₀, and the levels of organic carbon could be well estimated from the concentrations of dicarboxylic acids. Primary components of Ba, K, Sr, Cl⁻, Pb, Mg and secondary components of C₅H₆O₄²⁻, C₃H₂O₄²⁻, C₂O₄²⁻, C₄H₄O₄²⁻, SO₄²⁻, NO₃⁻ were over five times higher in the lantern days than in the normal days. The firework particles were acidic and of inorganic matter mostly with less amounts of secondary components. Primary aerosols from the burning of fireworks were mainly in the fine mode, while secondary formation of acidic anions mainly took place on the coarse particles. Nitrate was mainly formed through homogeneous gas-phase reactions of NO₂, while sulfate was largely from heterogeneous catalytic transformations of SO₂. Fe could catalyze the formation of nitrate through the reaction of α-Fe₂O₃ with HNO₃, while in the formation of sulfate, Fe is not only the catalyst, but also the oxidant. A simple method using the concentration of potassium and a modified method using the ratio of Mg/Al have been developed to quantify the source contribution of fireworks. It was found that over 90% of the total mineral aerosol and 98% of Pb, 43% of total carbon, 28% of Zn, 8% of NO₃⁻, and 3% of SO₄²⁻ in PM_2.5 were from the emissions of fireworks on the lantern night.” Ying Wang, Guoshun Zhuang, Chang Xu, Zhisheng An, Atmospheric Environment, Volume 41, Issue 2, January 2007, Pages 417-431, doi:10.1016/j.atmosenv.2006.07.043.

Measurement of fine particulate and gas-phase species during the New Year’s fireworks 2005 in Mainz, Germany – Drewnick et al. (2006) “The chemical composition and chemically resolved size distributions of fine aerosol particles were measured at high time resolution (5 min) with a time-of-flight aerosol mass spectrometer (TOF-AMS) during the New Year’s 2005 fireworks in Mainz, central Germany. In addition, particle number concentrations and trace gas concentrations were measured using a condensation particle counter (CPC) and a proton transfer reaction mass spectrometer (PTR-MS). The main non-refractory components of the firework aerosol were potassium, sulfate, total organics and chloride. Increased trace gas mixing ratios of methanol, acetonitrile, acetone and acetaldehyde were observed. Aerosol nitrate and ammonium concentrations were not significantly affected by the fireworks as well as the measured aromatic trace gases. The sub-micron aerosol concentrations peaked about 20 min after midnight with total mass concentrations larger than 600 μg m⁻³. The trace gas concentrations peaked about 30 min later. Using the sulfur-to-potassium concentration ratio measured in another fireworks aerosol, it was for the first time possible to estimate the relative ionization efficiency of aerosol potassium, measured with the TOF-AMS. Here we found a value of RIE_K=2.9.” Frank Drewnick, Silke S. Hings, Joachim Curtius, Gunter Eerdekens, Jonathan Williams, Atmospheric Environment, Volume 40, Issue 23, July 2006, Pages 4316-4327, doi:10.1016/j.atmosenv.2006.03.040. [Full text]

Short-term variation in air quality associated with firework events: A case study – Ravindra et al. (2003) “The effect of fireworks on air quality was assessed from the ambient concentrations of various air pollutants (SO₂, NO₂, PM₁₀ and TSP) during Diwali festival in Hisar city (India), in November 1999. The extensive use of fireworks was found to be related to short-term variation in air quality. During the festival the concentration of SO₂ was observed to be increased 10-fold at few sites, whereas the concentrations of NO₂, PM₁₀ and TSP increased 2–3 times, compared to the data collected on a typical winter day in December 1999. The maximum NO₂ concentration was observed a day after the festival. The diurnal pattern of the above pollutants showed a slight increase in the night. The levels of these pollutants observed during Diwali were found to be moderately high, which can be associated with serious health impacts.” Khaiwal Ravindra, Suman Mor and C. P. Kaushik, J. Environ. Monit., 2003, 5, 260-264, DOI: 10.1039/B211943A. [Full text]

Changes in forced expiratory flow due to air pollution from fireworks: Preliminary report – Smith & Dinh (1975) “Spirometry in humans and air sampling have been performed during a brief but intense bout of air pollution due to exploding fireworks on New Year’s Eve in Honolulu, Hawaii. An integrating nephelometer recorded a peak concentration of respirable particles in excess of 3.8 mg/m³. X-ray dispersive analysis, combined with scanning electron microscopy of particles collected with an Anderson cascade impactor, indicated that most of the small particles were probably crystals of KCl. Conditions were ideal for a possible SO₂KCl aerosol synergism which may have led to the measured changes in maximal midexpiratory flow (FEV_25–75%). Two male subjects with a history of chronic respiratory disease experienced an average decrease of 26% in FEV_25–75% when compared to that measured the previous night. Three normal males experienced a 4.7% decrease approaching statistical significance (0.1 > P > 0.05), but the overall difference in FEV_25–75% in healthy male and female subjects combined was not statistically significant. Thus, while susceptible people may be measurably affected, the general population of Honolulu probably experienced little, if any, change in FEV_25–75% with the air pollution levels reported here.” Richard Merrill Smith, Vu-Dinh Dinh, Environmental Research, Volume 9, Issue 3, June 1975, Pages 321-331, doi:10.1016/0013-9351(75)90012-2.

Observed decrease in Atlantic meridional overturning circulation is probably natural fluctuation

Observation of decadal change in the Atlantic meridional overturning circulation using 10 years of continuous transport data – Send et al. (2011)“The meridional overturning circulation (MOC) represents the main mechanism for the oceanic northward heat transport in the Atlantic, and fluctuations of this circulation are believed to have major impacts on northern hemisphere climate. While numerical ocean and climate models and paleo-records show large variability in this circulation, the use of direct observations of the MOC for detecting climate-timescale changes has proven difficult so far. This report presents the first observational record of MOC measurements that is continuous and sufficiently long to exhibit decadal-scale changes, here a decrease by 20% over the observational period (Jan. 2000–June 2009) and large interannual changes in the flow and its vertical structure. Data are from a mooring array at 16°N (Meridional Overturning Variability Experiment, MOVE). The observed change agrees with the amplitude of multi-decadal natural fluctuations seen in numerical ocean and climate models. Knowledge of the existence and phasing of such internal cycles provides multi-decadal climate predictability. Recently, some numerical model simulations have produced results that show a weakening of the MOC since the 1990′s and observational confirmation of this now is a high priority.” Send, U., M. Lankhorst, and T. Kanzow (2011), Geophys. Res. Lett., 38, L24606, doi:10.1029/2011GL049801.

Measurements and successful modelling of atmospheric carbon dioxide in 4-D

Three-dimensional variations of atmospheric CO2: aircraft measurements and multi-transport model simulations – Niwa et al. (2011)“Numerical simulation and validation of three-dimensional structure of atmospheric carbon dioxide (CO₂) is necessary for quantification of transport model uncertainty and its role on surface flux estimation by inverse modeling. Simulations of atmospheric CO₂ were performed using four transport models and two sets of surface fluxes compared with an aircraft measurement dataset of Comprehensive Observation Network for Trace gases by AIrLiner (CONTRAIL), covering various latitudes, longitudes, and heights. Under this transport model intercomparison project, spatiotemporal variations of CO₂ concentration for 2006–2007 were analyzed with a three-dimensional perspective. Results show that the models reasonably simulated vertical profiles and seasonal variations not only over northern latitude areas but also over the tropics and southern latitudes. From CONTRAIL measurements and model simulations, intrusion of northern CO₂ in to the Southern Hemisphere, through the upper troposphere, was confirmed. Furthermore, models well simulated the vertical propagation of seasonal variation in the northern free troposphere. However, significant model-observation discrepancies were found in Asian regions, which are attributable to uncertainty of the surface CO₂ flux data. In summer season, differences in latitudinal gradients by the fluxes are comparable to or greater than model-model differences even in the free troposphere. This result suggests that active summer vertical transport sufficiently ventilates flux signals up to the free troposphere and the models could use those for inferring surface CO₂ fluxes.” Niwa, Y., Patra, P. K., Sawa, Y., Machida, T., Matsueda, H., Belikov, D., Maki, T., Ikegami, M., Imasu, R., Maksyutov, S., Oda, T., Satoh, M., and Takigawa, M., Atmos. Chem. Phys., 11, 13359-13375, doi:10.5194/acp-11-13359-2011, 2011. [Full text]

Hansen et al. new paper on Earth’s energy imbalance

Earth’s energy imbalance and implications – Hansen et al. (2011)“Improving observations of ocean heat content show that Earth is absorbing more energy from the Sun than it is radiating to space as heat, even during the recent solar minimum. The inferred planetary energy imbalance, 0.58 ± 0.15 W m⁻² during the 6-yr period 2005–2010, confirms the dominant role of the human-made greenhouse effect in driving global climate change. Observed surface temperature change and ocean heat gain together constrain the net climate forcing and ocean mixing rates. We conclude that most climate models mix heat too efficiently into the deep ocean and as a result underestimate the negative forcing by human-made aerosols. Aerosol climate forcing today is inferred to be −1.6 ± 0.3 W m⁻², implying substantial aerosol indirect climate forcing via cloud changes. Continued failure to quantify the specific origins of this large forcing is untenable, as knowledge of changing aerosol effects is needed to understand future climate change. We conclude that recent slowdown of ocean heat uptake was caused by a delayed rebound effect from Mount Pinatubo aerosols and a deep prolonged solar minimum. Observed sea level rise during the Argo float era is readily accounted for by ice melt and ocean thermal expansion, but the ascendency of ice melt leads us to anticipate acceleration of the rate of sea level rise this decade.” Hansen, J., Sato, M., Kharecha, P., and von Schuckmann, K., Atmos. Chem. Phys., 11, 13421-13449, doi:10.5194/acp-11-13421-2011, 2011. [Full text]

Vegetation growth trend has decreased in China due to reduced precipitation

Recent change of vegetation growth trend in China – Peng et al. (2011)“Using satellite-derived normalized difference vegetation index (NDVI) data, several previous studies have indicated that vegetation growth significantly increased in most areas of China during the period 1982–99. In this letter, we extended the study period to 2010. We found that at the national scale the growing season (April–October) NDVI significantly increased by 0.0007 yr⁻¹ from 1982 to 2010, but the increasing trend in NDVI over the last decade decreased in comparison to that of the 1982–99 period. The trends in NDVI show significant seasonal and spatial variances. The increasing trend in April and May (AM) NDVI (0.0013 yr⁻¹) is larger than those in June, July and August (JJA) (0.0003 yr⁻¹) and September and October (SO) (0.0008 yr⁻¹). This relatively small increasing trend of JJA NDVI during 1982–2010 compared with that during 1982–99 (0.0012 yr⁻¹) (Piao et al 2003 J. Geophys. Res.—Atmos. 108 4401) implies a change in the JJA vegetation growth trend, which significantly turned from increasing (0.0039 yr⁻¹) to slightly decreasing ( − 0.0002 yr⁻¹) in 1988. Regarding the spatial pattern of changes in NDVI, the growing season NDVI increased (over 0.0020 yr⁻¹) from 1982 to 2010 in southern China, while its change was close to zero in northern China, as a result of a significant changing trend reversal that occurred in the 1990s and early 2000s. In northern China, the growing season NDVI significantly increased before the 1990s as a result of warming and enhanced precipitation, but decreased after the 1990s due to drought stress strengthened by warming and reduced precipitation. Our results also show that the responses of vegetation growth to climate change vary across different seasons and ecosystems.” Shushi Peng et al 2011 Environ. Res. Lett. 6 044027 doi:10.1088/1748-9326/6/4/044027. [Full text]

How coral communities survived past rapid warming events?

The evolution of mid Paleocene – early Eocene coral communities: How to survive during rapid global warming – Zamagni et al. (2011)“Today, diverse communities of zooxanthellate corals thrive, but do not build reef, under a wide range of environmental conditions. In these settings they inhabit natural bottom communities, sometimes forming patch-reefs, coral carpets and knobs. Episodes in the fossil record, characterized by limited coral-reef development but widespread occurrence of coral-bearing carbonates, may represent the fossil analogues of these non-reef building, zooxanthellate coral communities. If so, the study of these corals could have valuable implications for paleoenvironmental reconstructions. Here we focus on the evolution of early Paleogene corals as a fossil example of coral communities mainly composed by zooxanthellate corals (or likely zooxanthellate), commonly occurring within carbonate biofacies and with relatively high diversity but with a limited bioconstructional potential as testified by the reduced record of coral reefs. We correlate changes of bioconstructional potential and community compositions of these fossil corals with the main ecological/environmental conditions at that time. The early Paleogene greenhouse climate was characterized by relatively short pulses of warming with the most prominent occurring at the Paleocene-Eocene boundary (PETM event), associated with high weathering rates, nutrient fluxes, and pCO₂ levels. A synthesis of coral occurrences integrated with our data from the Adriatic Carbonate Platform (SW Slovenia) and the Minervois region (SW France), provide evidence for temporal changes in the reef-building capacity of corals associated with a shift in community composition towards forms adapted to tolerate deteriorating sea-water conditions. During the middle Paleocene coral-algal patch reefs and barrier reefs occurred from shallow-water settings, locally with reef-crest structures. A first shift can be traced from middle Paleocene to late Paleocene, with small coral-algal patch reefs and coral-bearing mounds development in shallow to intermediate water depths. In these mounds corals were highly subordinated as bioconstructors to other groups tolerant to higher levels of trophic resources (calcareous red algae, encrusting foraminifera, microbes, and sponges). A second shift occurred at the onset of the early Eocene with a further reduction of coral framework-building capacity. These coral communities mainly formed knobs in shallow-water, turbid settings associated with abundant foraminiferal deposits. We suggest that environmental conditions other than high temperature determined a combination of interrelated stressors that limited the coral-reef construction. A continuous enhancement of sediment load/nutrients combined with geochemical changes of ocean waters likely displaced corals as the main bioconstructors during the late Paleocene-early Eocene times. Nonetheless, these conditions did not affect the capacity of some corals to colonize the substrate, maintain biodiversity, and act as locally important carbonate-sediment producers, suggesting broad environmental tolerance limits of various species of corals. The implications of this study include clues as to how both ancient and modern zooxanthellate corals could respond to changing climate.” J. Zamagni, M. Mutti, A. Košir, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2011.12.010.

Increase in the global population living under water-stressed conditions

Modelling global water stress of the recent past: on the relative importance of trends in water demand and climate variability – Wada et al. (2011) “During the past decades, human water use has more than doubled, yet available freshwater resources are finite. As a result, water scarcity has been prevalent in various regions of the world. Here, we present the first global assessment of past development of water stress considering not only climate variability but also growing water demand, desalinated water use and non-renewable groundwater abstraction over the period 1960–2001 at a spatial resolution of 0.5°. Agricultural water demand is estimated based on past extents of irrigated areas and livestock densities. We approximate past economic development based on GDP, energy and household consumption and electricity production, which are subsequently used together with population numbers to estimate industrial and domestic water demand. Climate variability is expressed by simulated blue water availability defined by freshwater in rivers, lakes, wetlands and reservoirs by means of the global hydrological model PCR-GLOBWB. We thus define blue water stress by comparing blue water availability with corresponding net total blue water demand by means of the commonly used, Water Scarcity Index. The results show a drastic increase in the global population living under water-stressed conditions (i.e. moderate to high water stress) due to growing water demand, primarily for irrigation, which has more than doubled from 1708/818 to 3708/1832 km³ yr⁻¹ (gross/net) over the period 1960–2000. We estimate that 800 million people or 27% of the global population were living under water-stressed conditions for 1960. This number is eventually increased to 2.6 billion or 43% for 2000. Our results indicate that increased water demand is a decisive factor for heightened water stress in various regions such as India and North China, enhancing the intensity of water stress up to 200%, while climate variability is often a main determinant of extreme events. However, our results also suggest that in several emerging and developing economies (e.g. India, Turkey, Romania and Cuba) some of past extreme events were anthropogenically driven due to increased water demand rather than being climate-induced.” Wada, Y., van Beek, L. P. H., and Bierkens, M. F. P., Hydrol. Earth Syst. Sci., 15, 3785-3808, doi:10.5194/hess-15-3785-2011, 2011. [Full text]

Many surface albedo geoengineering schemes are useless for global climate change reversal

Climatic effects of surface albedo geoengineering – Irvine et al. (2011) “Various surface albedo modification geoengineering schemes such as those involving desert, urban, or agricultural areas have been proposed as potential strategies for helping counteract the warming caused by greenhouse gas emissions. However, such schemes tend to be inherently limited in their potential and would create a much more heterogeneous radiative forcing than propositions for space-based “reflectors” and enhanced stratospheric aerosol concentrations. Here we present results of a series of atmosphere–ocean general circulation model (GCM) simulations to compare three surface albedo geoengineering proposals: urban, cropland, and desert albedo enhancement. We find that the cooling effect of surface albedo modification is strongly seasonal and mostly confined to the areas of application. For urban and cropland geoengineering, the global effects are minor but, because of being colocated with areas of human activity, they may provide some regional benefits. Global desert geoengineering, which is associated with significant global-scale changes in circulation and the hydrological cycle, causes a smaller reduction in global precipitation per degree of cooling than sunshade geoengineering, 1.1% K⁻¹ and 2.0% K⁻¹ respectively, but a far greater reduction in the precipitation over land, 3.9% K⁻¹ compared with 1.0% K⁻¹. Desert geoengineering also causes large regional-scale changes in precipitation with a large reduction in the intensity of the Indian and African monsoons in particular. None of the schemes studied reverse the climate changes associated with a doubling of CO₂, with desert geoengineering profoundly altering the climate and with urban and cropland geoengineering providing only some regional amelioration at most.” Irvine, P. J., A. Ridgwell, and D. J. Lunt (2011), J. Geophys. Res., 116, D24112, doi:10.1029/2011JD016281.

Summer warming expected to permanently show up by 2020 over most areas of the continental United States

Transient regional climate change: Analysis of the summer climate response in a high-resolution, century-scale ensemble experiment over the continental United States – Diffenbaugh et al. (2011) “Integrating the potential for climate change impacts on policy and planning decisions requires quantification of the emergence of subregional climate changes that could occur in response to transient changes in global radiative forcing. Here we report results from a high-resolution, century-scale ensemble simulation of climate in the United States, forced by atmospheric constituent concentrations from the Special Report on Emissions Scenarios A1B scenario. We find that 21st century summer warming permanently emerges beyond the baseline decadal-scale variability prior to 2020 over most areas of the continental United States. Permanent emergence beyond the baseline annual-scale variability shows much greater spatial heterogeneity, with emergence occurring prior to 2030 over areas of the southwestern United States but not prior to the end of the 21st century over much of the south central and southeastern United States. The pattern of emergence of robust summer warming contrasts with the pattern of summer warming magnitude, which is greatest over the central United States and smallest over the western United States. In addition to stronger warming, the central United States also exhibits stronger coupling of changes in surface air temperature, precipitation, and moisture and energy fluxes, along with changes in atmospheric circulation toward increased anticylonic anomalies in the midtroposphere and a poleward shift in the midlatitude jet aloft. However, as a fraction of the baseline variability, the transient warming over the central United States is smaller than the warming over the southwestern or northeastern United States, delaying the emergence of the warming signal over the central United States. Our comparisons with observations and the Coupled Model Intercomparison Project Phase 3 ensemble of global climate model experiments suggest that near-term global warming is likely to cause robust subregional-scale warming over areas that exhibit relatively little baseline variability. In contrast, where there is greater variability in the baseline climate dynamics there can be greater variability in the response to elevated greenhouse forcing, decreasing the robustness of the transient warming signal.” Diffenbaugh, N. S., M. Ashfaq, and M. Scherer (2011), J. Geophys. Res., 116, D24111, doi:10.1029/2011JD016458.

New accurate 20 million year reconstruction of atmospheric CO2

Reconstruction of a continuous high-resolution CO2 record over the past 20 million years – van de Wal et al. (2011) “The gradual cooling of the climate during the Cenozoic has generally been attributed to a decrease in CO₂ concentration in the atmosphere. The lack of transient climate models and, in particular, the lack of high-resolution proxy records of CO₂, beyond the ice-core record prohibit, however, a full understanding of, for example, the inception of the Northern Hemisphere glaciation and mid-Pleistocene transition. Here we elaborate on an inverse modelling technique to reconstruct a continuous CO₂ series over the past 20 million year (Myr), by decomposing the global deep-sea benthic δ¹⁸O record into a mutually consistent temperature and sea level record, using a set of 1-D models of the major Northern and Southern Hemisphere ice sheets. We subsequently compared the modelled temperature record with ice core and proxy-derived CO₂ data to create a continuous CO₂ reconstruction over the past 20 Myr. Results show a gradual decline from 450 ppmv around 15 Myr ago to 225 ppmv for mean conditions of the glacial-interglacial cycles of the last 1 Myr, coinciding with a gradual cooling of the global surface temperature of 10 K. Between 13 to 3 Myr ago there is no long-term sea level variation caused by ice-volume changes. We find no evidence of change in the long-term relation between temperature change and CO₂, other than the effect following the saturation of the absorption bands for CO₂. The reconstructed CO₂ record shows that the Northern Hemisphere glaciation starts once the long-term average CO₂ concentration drops below 265 ppmv after a period of strong decrease in CO₂. Finally, only a small long-term decline of 23 ppmv is found during the mid-Pleistocene transition, constraining theories on this major transition in the climate system. The approach is not accurate enough to revise current ideas about climate sensitivity.” van de Wal, R. S. W., de Boer, B., Lourens, L. J., Köhler, P., and Bintanja, R., Clim. Past, 7, 1459-1469, doi:10.5194/cp-7-1459-2011, 2011. [Full text]

Shrubs are invading Arctic tundra

Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities – Myers-Smith et al. (2011) “Recent research using repeat photography, long-term ecological monitoring and dendrochronology has documented shrub expansion in arctic, high-latitude and alpine tundra ecosystems. Here, we (1) synthesize these findings, (2) present a conceptual framework that identifies mechanisms and constraints on shrub increase, (3) explore causes, feedbacks and implications of the increased shrub cover in tundra ecosystems, and (4) address potential lines of investigation for future research. Satellite observations from around the circumpolar Arctic, showing increased productivity, measured as changes in ‘greenness’, have coincided with a general rise in high-latitude air temperatures and have been partly attributed to increases in shrub cover. Studies indicate that warming temperatures, changes in snow cover, altered disturbance regimes as a result of permafrost thaw, tundra fires, and anthropogenic activities or changes in herbivory intensity are all contributing to observed changes in shrub abundance. A large-scale increase in shrub cover will change the structure of tundra ecosystems and alter energy fluxes, regional climate, soil–atmosphere exchange of water, carbon and nutrients, and ecological interactions between species. In order to project future rates of shrub expansion and understand the feedbacks to ecosystem and climate processes, future research should investigate the species or trait-specific responses of shrubs to climate change including: (1) the temperature sensitivity of shrub growth, (2) factors controlling the recruitment of new individuals, and (3) the relative influence of the positive and negative feedbacks involved in shrub expansion.” Isla H Myers-Smith et al 2011 Environ. Res. Lett. 6 045509 doi:10.1088/1748-9326/6/4/045509. [Full text]

Growing season has gotten longer for nothern vegetation

Recent changes in phenology over the northern high latitudes detected from multi-satellite data – Zeng et al. (2011) “Phenology of vegetation is a sensitive and valuable indicator of the dynamic responses of terrestrial ecosystems to climate change. Therefore, to better understand and predict ecosystems dynamics, it is important to reduce uncertainties in detecting phenological changes. Here, changes in phenology over the past several decades across the northern high-latitude region (≥60°N) were examined by calibrating and analyzing time series of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Very High Resolution Radiometer (AVHRR). Over the past decade (2000–10), an expanded length of the growing season (LOS) was detected by MODIS, largely due to an earlier start of the growing season (SOS) by 4.7 days per decade and a delayed end of the growing season (EOS) by 1.6 days per decade over the northern high latitudes. There were significant differences between North America and Eurasia in phenology from 2000 to 2010 based on MODIS data (SOS: df = 21, F = 49.02, p < 0.0001; EOS: df = 21, F = 49.25, p < 0.0001; LOS: df = 21, F = 79.40, p < 0.0001). In northern America, SOS advanced by 11.5 days per decade, and EOS was delayed by 2.2 days per decade. In Eurasia, SOS advanced by 2.7 days per decade, and EOS was delayed by 3.5 days per decade. SOS has likely advanced due to the warming Arctic during April and May. Our results suggest that in recent decades the longer vegetation growing seasons can be attributed to more advanced SOS rather than delayed EOS. AVHRR detected longer LOS over the past three decades, largely related to delayed EOS rather than advanced SOS. These two datasets are significantly different in key phenological parameters (SOS: df = 17, F = 14.63, p = 0.0015; EOS: df = 17, F = 38.69, p < 0.0001; LOS: df = 17, F = 16.47, p = 0.0009) from 2000 to 2008 over the northern high latitudes. Thus, further inter-calibration between the sensors is needed to resolve the inconsistency and to better understand long-term trends of vegetation growth in the Arctic.” Heqing Zeng et al 2011 Environ. Res. Lett. 6 045508 doi:10.1088/1748-9326/6/4/045508. [Full text]

Study on cloud changes with global warming

Computing and Partitioning Cloud Feedbacks using Cloud Property Histograms. Part II: Attribution to Changes in Cloud Amount, Altitude, and Optical Depth – Zelinka et al. (2011) “Cloud radiative kernels and histograms of cloud fraction, both as functions of cloud top pressure and optical depth, are used to quantify cloud amount, altitude, and optical depth feedbacks. The analysis is applied to doubled CO2 simulations from eleven global climate models in the Cloud Feedback Model Intercomparison Project. Global, annual, and ensemble mean longwave (LW) and shortwave (SW) cloud feedbacks are positive, with the latter nearly twice as as large as the former. The robust increase in cloud top altitude is the dominant contributor to the positive LW cloud feedback. The negative impact of reductions in cloud amount offsets more than half of the positive impact of rising clouds on LW cloud feedback, but the magnitude of compensation varies considerably across models. In contrast, robust reductions in cloud amount make a large and virtually unopposed positive contribution to SW cloud feedback, though the inter-model spread is greater than for any other individual feedback component. Overall reductions in cloud amount have twice as large an impact on SW fluxes as on LW fluxes such that the net cloud amount feedback is moderately positive, with no models exhibiting a negative value. As a consequence of large but partially offsetting effects of cloud amount reductions on LW and SW feedbacks, both the mean and inter-model spread in net cloud amount feedback are smaller than those of the net cloud altitude feedback. Finally, we find that the large negative cloud feedback at high latitudes results from robust increases in cloud optical depth, not from increases in total cloud amount as is commonly assumed.” Mark D. Zelinka, Stephen A. Klein, Dennis L. Hartmann, Journal of Climate 2011, doi: http://dx.doi.org/10.1175/JCLI-D-11-00249.1. [Full text]

Clean coal power comes with side-effects

The climate penalty for clean fossil fuel combustion – Junkermann et al. (2011) “To cope with the world’s growing demand for energy, a large number of coal-fired power plants are currently in operation or under construction. To prevent environmental damage from acidic sulphur and particulate emissions, many such installations are equipped with flue gas cleaning technology that reduces the emitted amounts of sulphur dioxide (SO2) and nitrogen dioxide (NO2). However, the consequences of this technology for aerosol emissions, and in particular the regional scale impact on cloud microphysics, have not been studied until now. We performed airborne investigations to measure aerosol size distributions in the air masses downwind of coal-fired power installations. We show how the current generation of clean technology reduces the emission of sulphur and fine particulate matter, but leads to an unanticipated increase in the direct emission of ultrafine particles (1–10 nm median diameter) which are highly effective precursors of cloud condensation nuclei (CCN). Our analysis shows how these additional ultrafine particles probably modify cloud microphysics, as well as precipitation intensity and distribution on a regional scale downwind of emission sources. Effectively, the number of small water droplets might be increased, thus reducing the water available for large droplets and rain formation. The possible corresponding changes in the precipitation budget with a shift from more frequent steady rain to occasionally more vigorous rain events, or even a significant regional reduction of annual precipitation, introduce an unanticipated risk for regional climate and agricultural production, especially in semi-arid climate zones.” Junkermann, W., Vogel, B., and Sutton, M. A., Atmos. Chem. Phys., 11, 12917-12924, doi:10.5194/acp-11-12917-2011, 2011. [Full text]

Madden-Julian Oscillation contributes to Arctic amplification

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), Geophys. Res. Lett., 38, L24804, doi:10.1029/2011GL049881.

Millennial-scale climate cycles might have been active throughout geologic time

Millennial-scale climate cycles in Permian–Carboniferous rhythmites: Permanent feature throughout geologic time? – Franco et al. (2011) “Two late Paleozoic glacial rhythmite successions from the Itararé Group (Paraná Basin, Brazil) were examined for paleoclimate variations. Paleomagnetic (characteristic remanent magnetization, ChRM) and magnetic susceptibility (K_z) measurements taken from the rhythmites are interpreted as paleoclimatic proxies. Ratios of low-frequency components in the K_z variations suggest Milankovitch periodicities; this leads to recognition of other, millennial-scale variations reminiscent of abrupt climate changes during late Quaternary time, and are suggestive of Bond cycles and the 2.4 k.y. solar cycle. We infer from these patterns that millennial-scale climate change is not restricted to the Quaternary Period, and that millennial forcing mechanisms may have been prevalent throughout geologic time.” Daniel R. Franco, Linda A. Hinnov and Marcia Ernesto, Geology, v. 40 no. 1 p. 19-22, doi: 10.1130/G32338.1.

El Niño might not have been permanent during Late Cretaceous

El Niño–Southern Oscillation variability from the Late Cretaceous Marca Shale of California – Davies et al. (2011) “Changes in the possible behavior of El Niño–Southern Oscillation (ENSO) with global warming have provoked interest in records of ENSO from past “greenhouse” climate states. The latest Cretaceous laminated Marca Shale of California permits a seasonal-scale reconstruction of water column flux events and hence interannual paleoclimate variability. The annual flux cycle resembles that of the modern Gulf of California with diatoms characteristic of spring upwelling blooms followed by silt and clay, and is consistent with the existence of a paleo–North American Monsoon that brought input of terrigenous sediment during summer storms and precipitation runoff. Variation is also indicated in the extent of water column oxygenation by differences in lamina preservation. Time series analysis of interannual variability in terrigenous sediment and diatom flux and in the degree of bioturbation indicates strong periodicities in the quasi-biennial (2.1–2.8 yr) and low-frequency (4.1–6.3 yr) bands both characteristic of ENSO forcing, as well as decadal frequencies. This evidence for robust Late Cretaceous ENSO variability does not support the theory of a “permanent El Niño,” in the sense of a continual El Niño–like state, in periods of warmer climate.” Andrew Davies, Alan E.S. Kemp, Graham P. Weedon and John A. Barron, Geology, v. 40 no. 1 p. 15-18, doi: 10.1130/G32329.1.

Developing methods for model performance comparison with observations

On the observational assessment of climate model performance – Annan et al. (2011) “Comparison of model outputs with observations of the climate system forms an essential component of model assessment and is crucial for building our confidence in model predictions. Methods for undertaking this comparison are not always clearly justified and understood. Here we show that the popular approach of comparing the ensemble spread to a so-called “observationally-constrained pdf” can be highly misleading. Such a comparison will almost certainly result in disagreement, but in reality tells us little about the performance of the ensemble. We present an alternative approach, and show how it may lead to very different, and rather more encouraging, conclusions. We additionally present some necessary conditions for an ensemble (or more generally, a probabilistic prediction) to be challenged by an observation.” Annan, J. D., J. C. Hargreaves, and K. Tachiiri (2011), Geophys. Res. Lett., 38, L24702, doi:10.1029/2011GL049812.

Revealing annual ice core layers from Eemian interglacial

Annual layering in the NGRIP ice core during the Eemian – Svensson et al. (2011) “The Greenland NGRIP ice core continuously covers the period from present day back to 123 ka before present, which includes several thousand years of ice from the previous interglacial period, MIS 5e or the Eemian. In the glacial part of the core, annual layers can be identified from impurity records and visual stratigraphy, and stratigraphic layer counting has been performed back to 60 ka. In the deepest part of the core, however, the ice is close to the pressure melting point, the visual stratigraphy is dominated by crystal boundaries, and annual layering is not visible to the naked eye. In this study, we apply a newly developed setup for high-resolution ice core impurity analysis to produce continuous records of dust, sodium and ammonium concentrations as well as conductivity of melt water. We analyzed three 2.2 m sections of ice from the Eemian and the glacial inception. In all of the analyzed ice, annual layers can clearly be recognized, most prominently in the dust and conductivity profiles. Part of the samples is, however, contaminated in dust, most likely from drill liquid. It is interesting that the annual layering is preserved despite a very active crystal growth and grain boundary migration in the deep and warm NGRIP ice. Based on annual layer counting of the new records, we determine a mean annual layer thickness close to 11 mm for all three sections, which, to first order, confirms the modeled NGRIP time scale (ss09sea). The counting does, however, suggest a longer duration of the climatically warmest part of the NGRIP record (MIS5e) of up to 1 ka as compared to the model estimate. Our results suggest that stratigraphic layer counting is possible basically throughout the entire NGRIP ice core, provided sufficiently highly-resolved profiles become available.” Svensson, A., Bigler, M., Kettner, E., Dahl-Jensen, D., Johnsen, S., Kipfstuhl, S., Nielsen, M., and Steffensen, J. P., Clim. Past, 7, 1427-1437, doi:10.5194/cp-7-1427-2011, 2011. [Full text]

Assessment of Southern Hemisphere paleoclimate records

Southern Hemisphere high-resolution palaeoclimate records of the last 2000 years – Neukom & Gergis (2011) “This study presents a comprehensive assessment of high-resolution Southern Hemisphere (SH) paleoarchives covering the last 2000 years. We identified 174 monthly to annually resolved climate proxy (tree ring, coral, ice core, documentary, speleothem and sedimentary) records from the Hemisphere. We assess the interannual and decadal sensitivity of each proxy record to large-scale circulation indices from the Pacific, Indian and Southern Ocean regions over the twentieth century. We then analyse the potential of this newly expanded palaeoclimate network to collectively represent predictands (sea surface temperature, sea level pressure, surface air temperature and precipitation) commonly used in climate reconstructions. The key dynamical centres-of-action of the equatorial Indo-Pacific are well captured by the palaeoclimate network, indicating that there is considerable reconstruction potential in this region, particularly in the post AD 1600 period when a number of long coral records are available. Current spatiotemporal gaps in data coverage and regions where significant potential for future proxy collection exists are discussed. We then highlight the need for new and extended records from key dynamical regions of the Southern Hemisphere. Although large-scale climate field reconstructions for the SH are in their infancy, we report that excellent progress in the development of regional proxies now makes plausible estimates of continental- to hemispheric-scale climate variations possible.” Raphael Neukom, Joëlle Gergis, The Holocene December 16, 2011 0959683611427335, doi: 10.1177/0959683611427335.

Warmer climate makes heavy rain heavier and more frequent and weak rain weaker and less frequent

Mechanisms for global warming impacts on rainfall frequency and intensity – Chou et al. (2011) “Global warming mechanisms that cause changes in frequency and intensity of precipitation in the tropics are examined in climate model simulations. Under global warming, tropical precipitation tends to be more frequent and intense for heavy precipitation, but becomes less frequent and weaker for light precipitation. Changes in precipitation frequency and intensity are both controlled by thermodynamic and dynamic components. The thermodynamic component is induced by changes in atmospheric water vapor, while the dynamic component is associated with changes in vertical motion. A set of equations is derived to estimate both thermodynamic and dynamic contributions to changes in frequency and intensity of precipitation, especially for heavy precipitation. In the thermodynamic contribution, increased water vapor reduces the magnitude of the required vertical motion to generate the same strength of precipitation, so precipitation frequency increases. Increased water vapor also intensifies precipitation due to the enhancement of water vapor availability in the atmosphere. In the dynamic contribution, the more stable atmosphere tends to reduce the frequency and intensity of precipitation, except for the heaviest precipitation. The dynamic component strengthens the heaviest precipitation in most climate model simulations, possibly due to a positive convective feedback.” Chia Chou, Chao-An Chen, Pei-Hua Tan, Kuan Ting Chen, Journal of Climate 2011, doi: http://dx.doi.org/10.1175/JCLI-D-11-00239.1.

We know how Greenland outlet glaciers respond to warming but how they respond to cooling?

Response of a marine-terminating Greenland outlet glacier to abrupt cooling 8200 and 9300 years ago – Young et al. (2011) “Long-term records of Greenland outlet-glacier change extending beyond the satellite era can inform future predictions of Greenland Ice Sheet behavior. Of particular relevance is elucidating the Greenland Ice Sheet’s response to decadal- and centennial-scale climate change. Here, we reconstruct the early Holocene history of Jakobshavn Isbræ, Greenland’s largest outlet glacier, using ¹⁰Be surface exposure ages and ¹⁴C-dated lake sediments. Our chronology of ice-margin change demonstrates that Jakobshavn Isbræ advanced to deposit moraines in response to abrupt cooling recorded in central Greenland ice cores ca. 8,200 and 9,300 years ago. While the rapid, dynamically aided retreat of many Greenland outlet glaciers in response to warming is well documented, these results indicate that marine-terminating outlet glaciers are also able to respond quickly to cooling. We suggest that short lag times of high ice flux margins enable a greater magnitude response of marine-terminating outlets to abrupt climate change compared to their land-terminating counterparts.” Young, N. E., J. P. Briner, Y. Axford, B. Csatho, G. S. Babonis, D. H. Rood, and R. C. Finkel (2011), Geophys. Res. Lett., 38, L24701, doi:10.1029/2011GL049639.

The rise but not fall of Taku Glacier late summer transient snowline

Utility of late summer transient snowline migration rate on Taku Glacier, Alaska – Pelto (2011) “On Taku Glacier, Alaska a combination of field observations of snow water equivalent (SWE) from snowpits and probing in the vicinity of the transient snowline (TSL) are used to quantify the mass balance gradient. The balance gradient derived from the TSL and SWE measured in snowpits at 1000 m from 1998–2010 ranges from 2.6–3.8 mm m⁻¹. Probing transects from 950 m–1100 m directly measure SWE and yield a slightly higher balance gradient of 3.3–3.8 mm m⁻¹. The TSL on Taku Glacier is identified in MODIS and Landsat 4 and 7 Thematic Mapper images for 31 dates during the 2004–2010 period to assess the consistency of its rate of rise and reliability in assessing ablation for mass balance assessment. For example, in 2010, the TSL was 750 m on 28 July, 800 m on 5 August, 875 m on 14 August, 925 m on 30 August, and 975 m on 20 September. The mean observed probing balance gradient was 3.3 mm m⁻¹, combined with the TSL rise of 3.7 m day⁻¹ yields an ablation rate of 12.2 mm day⁻¹ from mid-July to mid-Sept, 2010. The TSL rise in the region from 750–1100 m on Taku Glacier during eleven periods each covering more than 14 days during the ablation season indicates a mean TSL rise of 3.7 m day⁻¹, the rate of rise is relatively consistent ranging from 3.1 to 4.4 m day⁻¹. This rate is useful for ascertaining the final ELA if images or observations are not available near the end of the ablation season. The mean ablation from 750–1100 m during the July–September period determined from the TSL rise and the observed balance gradient is 11–13 mm day⁻¹ on Taku Glacier during the 2004–2010 period. The potential for providing an estimate of b_n from TSL observations late in the melt season from satellite images combined with the frequent availability of such images provides a means for efficient mass balance assessment in many years and on many glaciers.” Pelto, M., The Cryosphere, 5, 1127-1133, doi:10.5194/tc-5-1127-2011, 2011. [Full text]

Review article on North Atlantic Oscillation

Past and recent changes in the North Atlantic oscillation – Pinto & Raible (2011) “The North Atlantic oscillation (NAO) is under current climate conditions the leading mode of atmospheric circulation variability over the North Atlantic region. While the pattern is present during the entire year, it is most important during winter, explaining a large part of the variability of the large-scale pressure field, being thus largely determinant for the weather conditions over the North Atlantic basin and over Western Europe. In this study, a review of recent literature on the basic understanding of the NAO, its variability on different time scales and driving physical mechanisms is presented. In particular, the observed NAO variations and long-term trends are put into a long term perspective by considering paleo-proxy evidence. A representative number of recently released NAO reconstructions are discussed. While the reconstructions agree reasonably well with observations during the instrumental overlapping period, there is a rather high uncertainty between the different reconstructions for the pre-instrumental period, which leads to partially incoherent results, that is, periods where the NAO reconstructions do not agree even in sign. Finally, we highlight the future need of a broader definition of the NAO, the assessment of the stability of the teleconnection centers over time, the analysis of the relations to other relevant variables like temperature and precipitation, as well as on the relevant processes involved.” Joaquim G. Pinto, Christoph C. Raible, Wiley Interdisciplinary Reviews: Climate Change, DOI: 10.1002/wcc.150.

New review article looks at geological fakes and frauds

Geological Fakes and Frauds – Ruffell et al. (2011) “Some geological fakes and frauds are carried out solely for financial gain (mining fraud), whereas others maybe have increasing aesthetic appeal (faked fossils) or academic advancement (fabricated data) as their motive. All types of geological fake or fraud can be ingenious and sophisticated, as demonstrated in this article. Fake gems, faked fossils and mining fraud are common examples where monetary profit is to blame: nonetheless these may impact both scientific theory and the reputation of geologists and Earth scientists. The substitution or fabrication of both physical and intellectual data also occurs for no direct financial gain, such as career advancement or establishment of belief (e.g. evolution vs. creationism). Knowledge of such fakes and frauds may assist in spotting undetected geological crimes: application of geoforensic techniques helps the scientific community to detect such activity, which ultimately undermines scientific integrity.” Alastair Ruffell, Niall Majury, William E. Brooks, Earth-Science Reviews, doi:10.1016/j.earscirev.2011.12.001.

Moon affects the weather

Monthly lunar declination extremes’ influence on tropospheric circulation patterns – Krahenbuhl et al. (2011) “Short-term tidal variations occurring every 27.3 days from southern (negative) to northern (positive) maximum lunar declinations (MLDs), and back to southern declination of the moon have been overlooked in weather studies. These short-term MLD variations’ significance is that when lunar declination is greatest, tidal forces operating on the high latitudes of both hemispheres are maximized. We find that such tidal forces deform the high latitude Rossby longwaves. Using the NCEP/NCAR reanalysis data set, we identify that the 27.3 day MLD cycle’s influence on circulation is greatest in the upper troposphere of both hemispheres’ high latitudes. The effect is distinctly regional with high impact over central North America and the British Isles. Through this lunar variation, midlatitude weather forecasting for two-week forecast periods may be significantly improved.” Krahenbuhl, D. S., M. B. Pace, R. S. Cerveny, and R. C. Balling Jr. (2011), J. Geophys. Res., 116, D23121, doi:10.1029/2011JD016598.

Climate change makes some interacting species drift apart

Increasing range mismatching of interacting species under global change is related to their ecological characteristics – Schweiger et al. (2011) “Aim: We investigate the importance of interacting species for current and potential future species distributions, the influence of their ecological characteristics on projected range shifts when considering or ignoring interacting species, and the consistency of observed relationships across different global change scenarios. Location: Europe. Methods: We developed ecological niche models (generalized linear models) for 36 European butterfly species and their larval host plants based on climate and land-use data. We projected future distributional changes using three integrated global change scenarios for 2080. Observed and projected mismatches in potential butterfly niche space and the niche space of their hosts were first used to assess changing range limitations due to interacting species and then to investigate the importance of different ecological characteristics. Results: Most butterfly species were primarily limited by climate. Species dwelling in warm areas of Europe and tolerant to large variations in moisture conditions were projected to suffer less from global change. However, a gradient from climate to host plant control was apparent, reflecting the range size of the hosts. Future projections indicated increased mismatching of already host-plant-limited butterflies and their hosts. Butterflies that utilize plants with restricted ranges were projected to suffer most from global change. The directions of these relationships were consistent across the scenarios but the level of spatial mismatching of butterflies and their host plants increased with the severity of the scenario. Main conclusions: Future changes in the co-occurrence of interacting species will depend on political and socio-economic development, suggesting that the composition of novel communities due to global change will depend on the way we create our future. A better knowledge of ecological species characteristics can be utilized to project the future fate and potential risk of extinction of interacting species leading to a better understanding of the consequences of changing biotic interactions. This will further enhance our abilities to assess and mitigate potential negative effects on ecosystem functions and services.” Oliver Schweiger, Risto K. Heikkinen, Alexander Harpke, Thomas Hickler, Stefan Klotz, Otakar Kudrna, Ingolf Kühn, Juha Pöyry, Josef Settele, Global Ecology and Biogeography, Special Issue: QUO VADIS, ECOSYSTEM? SCENARIOS AS A TOOL FOR LARGE-SCALE ECOLOGICAL RESEARCH, Volume 21, Issue 1, pages 88–99, January 2012, DOI: 10.1111/j.1466-8238.2010.00607.x. [Full text]

When climate warms California valley oaks gather around water bodies

Predicting species responses to climate change: demography and climate microrefugia in California valley oak (Quercus lobata) – Mclaughlin & Zavaleta (2011) “Anticipating species movement under climate change is a major focus in conservation. Bioclimate models are one of the few predictive tools for adaptation planning, but are limited in accounting for (1) climatic tolerances in pre-adult life stages that are potentially more vulnerable to warming; and (2) local-scale movement and use of climatic refugia as an alternative or complement to large-scale changes in distribution. To assess whether these shortfalls can be addressed with field demographic data, we used California valley oak (Quercus lobata Nee), a long-lived species with juvenile life stages known to be sensitive to climate. We hypothesized that the valley oak bioclimate model, based on adults, would overpredict the species’ ability to remain in the projected persisting area, due to higher climate vulnerability of young life stages; and underpredict the potential for the species to remain in the projected contracting area in local-scale refugia. We assessed the bioclimate model projections against actual demographic patterns in natural populations. We found that saplings were more constricted around surface water than adults in the projected contracting area. We also found that the climate envelope for saplings is narrower than that for adults. Saplings disappeared at a summer maximum temperature 3 degrees C below that associated with adults. Our findings indicate that rather than a complete shift northward and upward, as predicted by the species bioclimate model, valley oaks are more likely to experience constriction around water bodies, and eventual disappearance from areas exceeding a threshold of maximum temperature. Ours is the first study we know of to examine the importance of discrete life stage climate sensitivities in determining bioclimate modeling inputs, and to identify current climate change-related constriction of a species around microrefugia. Our findings illustrate that targeted biological fieldwork can be central to understanding climate change-related movement for long-lived, sessile species.” B.C. Mclaughlin, E.S. Zavaleta, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02630.x.

There’s a general warming trend over western North America

Climatic changes in western North America, 1950–2005 – Booth et al. (2011) “The rate of climatic change over western North America (WNA) is quantified for 485 climate stations for the period 1950–2005. Additionally, six stations with quality long-term records were selected and analysed for the period 1906–2005. The indicators used were developed by the World Meteorological Organization (WMO) and the World Climate Research Program’s Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI). From the 27 core indices, 4 temperature-based and 4 precipitation-based indicators were selected for in-depth analysis. The 8 million km2 study area is comprised of the 22 contiguous US states and 4 Canadian provinces west of the Mississippi River and Great Lakes. The results were divided into six general regions for interpretation and presentation. GIS interpolation of station-specific statistical output was completed to further aid in the identification of spatially coherent trends across WNA. Mean slopes were calculated over the whole study area, and by region, for each index, and then tested to determine if they were significantly different from zero. Results of the study show statistically significant historical climate trends across the study area. As expected in a region as geographically diverse as WNA, results differed between, and within, regions. Overall, temperature-based indicators showed a general warming trend over the entire study area, with the greatest increases along the North American Cordillera. The trends in precipitation-based indicators were more varied. General trends indicate moderately increasing precipitation volume and intensity over much of WNA. The strongest precipitation trends were found in areas with climate largely controlled by air masses originating over the Gulf of Mexico.” Evan L. J. Booth, James M. Byrne, Dan L. Johnson, International Journal of Climatology, DOI: 10.1002/joc.3401.

Climate warms but hot spell mortality declines in Czech Republic

Declining impacts of hot spells on mortality in the Czech Republic, 1986–2009: adaptation to climate change? – Kyselý & Plavcová (2011) “The study examines temporal changes in mortality associated with spells of large positive temperature anomalies (hot spells) in extended summer season in the population of the Czech Republic (Central Europe) during 1986–2009. Declining trends in the mortality impacts are found in spite of rising temperature trends. The finding remains unchanged if possible confounding effects of within-season acclimatization to heat and the mortality displacement effect are taken into account. Recent positive socioeconomic development, following the collapse of communism in Central and Eastern Europe in 1989, and better public awareness of heat-related risks are likely the primary causes of the declining vulnerability. The results suggest that climate change may have relatively little influence on heat-related deaths, since changes in other factors that affect vulnerability of the population are dominant instead of temperature trends. It is essential to better understand the observed nonstationarity of the temperature-mortality relationship and the role of adaptation and its limits, both physiological and technological, and to address associated uncertainties in studies dealing with climate change projections of temperature-related mortality.” Jan Kyselý and Eva Plavcová, Climatic Change, DOI: 10.1007/s10584-011-0358-4.

Frequency of extremely high temperatures has increased 10-fold since early 20th century

Climate change: a new metric to measure changes in the frequency of extreme temperatures using record data – Munasinghe et al. (2011) “Consensus on global warming is the result of multiple and varying lines of evidence, and one key ramification is the increase in frequency of extreme climate events including record high temperatures. Here we develop a metric—called “record equivalent draws” (RED)—based on record high (low) temperature observations, and show that changes in RED approximate changes in the likelihood of extreme high (low) temperatures. Since we also show that this metric is independent of the specifics of the underlying temperature distributions, RED estimates can be aggregated across different climates to provide a genuinely global assessment of climate change. Using data on monthly average temperatures across the global landmass we find that the frequency of extreme high temperatures increased 10-fold between the first three decades of the last century (1900–1929) and the most recent decade (1999–2008). A more disaggregated analysis shows that the increase in frequency of extreme high temperatures is greater in the tropics than in higher latitudes, a pattern that is not indicated by changes in mean temperature. Our RED estimates also suggest concurrent increases in the frequency of both extreme high and extreme low temperatures during 2002–2008, a period when we observe a plateauing of global mean temperature. Using daily extreme temperature observations, we find that the frequency of extreme high temperatures is greater in the daily minimum temperature time-series compared to the daily maximum temperature time-series. There is no such observable difference in the frequency of extreme low temperatures between the daily minimum and daily maximum.” Lalith Munasinghe, Tackseung Jun and David H. Rind, Climatic Change, DOI: 10.1007/s10584-011-0370-8.

Pacific Decadal Oscillation might contribute to tropical belt widening

Effects of the PDO phase on the tropical belt width – Grassi et al. (2011) “Recent studies have shown that the Tropical Belt (TB) has progressively expanded since at least the late 1970′s. This trend has been largely attributed to the radiative forcing due to GHG increase and stratospheric ozone depletion, even if an influence of Sea Surface Temperature (SST) anomalies has been also suggested. In this work we investigate the impact of the Pacific Decadal Oscillation (PDO) on the TB width. The study is performed by using both AMIP (Atmospheric Model Intercomparison Project) and idealized simulations, produced by NCAR/CAM3 GCM, and reanalysis data (ERA-Interim, ERA-40 and MERRA). Reanalysis show that a switch of the PDO from a positive to a negative phase can lead to a significant TB expansion during the equinoxes. This effect, indicating a possible PDO contribution to the widening that characterized the TB width during the last decades, is not correctly reproduced by model simulations. Deficiencies in the sensitivity of model simulated convective processes to SST anomalies are suggested as a possible cause of the TB widening underestimation.” Barbara Grassi, Gianluca Redaelli, Pablo Osvaldo Canziani, and Guido Visconti, Journal of Climate 2011, doi: http://dx.doi.org/10.1175/JCLI-D-11-00244.1.

Evaluating anthropogenic carbon and its effect to pH in South Pacific Ocean

Changes in South Pacific anthropogenic carbon – Waters et al. (2011) “The changes in anthropogenic CO₂ are evaluated in the South Pacific, along the meridional line P18 (110°W) and the zonal line P06 (32°S), using the extended multiple linear regression (eMLR) method. The structure of the column inventory of anthropogenic CO₂ on P18 is similar to the southern section of P16 in the central South Pacific (150°W), but the overall increase is greater by approximately 5–10 μmol kg⁻¹. The value of the anthropogenic CO₂ inventory on P18 is in agreement at the crossover point of an earlier evaluation of P06. Subsequent changes in pH due to the increase in anthropogenic CO₂ are also evaluated. The change in pH is determined from the changes in anthropogenic CO₂ and do not reflect variability in other decadal signals. For both cruise tracks, the average annual change in pH is −0.0016 mol kg⁻¹ yr⁻¹. This value is in good agreement with the average decrease in pH in the North Pacific, at the Hawaii Times Series and the subtropical North Atlantic. The uptake rates of anthropogenic CO₂ are within reasonable agreement with similar studies in the South Pacific. There is evidence for greater uptake of anthropogenic CO₂ in the western South Pacific and is attributed to the formation of subtropical Mode Water in the region.” Waters, J. F., F. J. Millero, and C. L. Sabine (2011), Global Biogeochem. Cycles, 25, GB4011, doi:10.1029/2010GB003988.

Nuclear power industry affects atmospheric radiocarbon concentration

Continental-scale enrichment of atmospheric ¹⁴CO₂ from the nuclear power industry: potential impact on the estimation of fossil fuel-derived CO₂ - Graven & Gruber (2011) “The ¹⁴C-free fossil carbon added to atmospheric CO₂ by combustion dilutes the atmospheric ¹⁴C/C ratio (Δ¹⁴C), potentially providing a means to verify fossil CO₂ emissions calculated using economic inventories. However, sources of ¹⁴C from nuclear power generation and spent fuel reprocessing can counteract this dilution and may bias ¹⁴C/C-based estimates of fossil fuel-derived CO₂ if these nuclear influences are not correctly accounted for. Previous studies have examined nuclear influences on local scales, but the potential for continental-scale influences on Δ¹⁴C has not yet been explored. We estimate annual ¹⁴C emissions from each nuclear site in the world and conduct an Eulerian transport modeling study to investigate the continental-scale, steady-state gradients of Δ¹⁴C caused by nuclear activities and fossil fuel combustion. Over large regions of Europe, North America and East Asia, nuclear enrichment may offset at least 20% of the fossil fuel dilution in Δ¹⁴C, corresponding to potential biases of more than −0.25 ppm in the CO₂ attributed to fossil fuel emissions, larger than the bias from plant and soil respiration in some areas. Model grid cells including high ¹⁴C-release reactors or fuel reprocessing sites showed much larger nuclear enrichment, despite the coarse model resolution of 1.8°×1.8°. The recent growth of nuclear ¹⁴C emissions increased the potential nuclear bias over 1985–2005, suggesting that changing nuclear activities may complicate the use of Δ¹⁴C observations to identify trends in fossil fuel emissions. The magnitude of the potential nuclear bias is largely independent of the choice of reference station in the context of continental-scale Eulerian transport and inversion studies, but could potentially be reduced by an appropriate choice of reference station in the context of local-scale assessments.” Graven, H. D. and Gruber, N., Atmos. Chem. Phys., 11, 12339-12349, doi:10.5194/acp-11-12339-2011, 2011. [Full text]

Human actions are seen in borehole temperatures in Czechia and Slovenia

Detection and quantification of local anthropogenic and regional climatic transient signals in temperature logs from Czechia and Slovenia – Dědeček et al. (2011) “The paper reports on detection and quantification of the impact of local anthropogenic structures and regional climatic changes on subsurface temperature field. The analyzed temperature records were obtained by temperature monitoring in a borehole in Prague-Spořilov (Czechia) and by repeated logging of a borehole in Šempeter (Slovenia). The observed data were compared with temperatures yielded by mathematical 3D time-variable geothermal models of the boreholes’ sites with the aim to decompose the observed transient component of the subsurface temperature into the part affected by construction of new buildings and other anthropogenic structures in surroundings of the boreholes and into the part affected by the ground surface temperature warming due to the surface air temperature rise. A direct human impact on the subsurface temperature warming was proved and contributions of individual anthropogenic structures to this change were evaluated. In the case of Spořilov, where the mean annual warming rate reached 0.034°C per year at the depth of 38.3 m during the period 1993–2008, it turned out that about half of the observed warming can be attributed to the air (ground) surface temperature change and half to the human activity on the surface in the immediate vicinity of the borehole. The situation is similar in Šempeter, where the effect of the recently built surface anthropogenic structures is detectable down to the depth of 80 m and the share of the anthropogenic signal on the non-stationary component of the observed subsurface temperature amounts to 30% at the depth of 50 m.” Petr Dědeček, Jan Šafanda and Dušan Rajver, Climatic Change, DOI: 10.1007/s10584-011-0373-5.

CO2 emissions matter to German car buyers

German car buyers’ willingness to pay to reduce CO2 emissions – Achtnicht (2011) “Motorized individual transport strongly contributes to global CO2 emissions, due to its intensive usage of fossil fuels. Current political efforts addressing this issue (i.e. emission performance standards in the EU) are directed towards car manufacturers. This paper focuses on the demand side. It examines whether CO2 emissions per kilometer is a relevant attribute in car choices. Based on a choice experiment among potential car buyers from Germany, a mixed logit specification is estimated. In addition, distributions of willingness-to-pay measures for an abatement of CO2 emissions are obtained. The results suggest that the emissions performance of a car matters substantially, but its consideration varies heavily across the sampled population. In particular, some evidence on gender, age and education effects on climate concerns is provided.” Martin Achtnicht, Climatic Change, DOI: 10.1007/s10584-011-0362-8.

Arctic Oscillation shows up in Swiss aquifers

Regime shift in groundwater temperature triggered by the Arctic Oscillation – Figura et al. (2011) “Groundwater is the world’s most important source of raw drinking water. However, the potential impact of climate change on this vital resource is unclear because of a lack of relevant long-term data. Here we statistically analyze over 20 years of groundwater temperature data from five Swiss aquifers fed predominantly by river-bank infiltration. The results reveal an abrupt increase in annual mean groundwater temperature centered on 1987–1988 that can also be observed in air and river temperatures. We associate this temperature increase with the Northern Hemisphere late 1980s climate regime shift (CRS), which itself is related to an abrupt change in the behavior of the Arctic Oscillation. Because temperature affects redox conditions in groundwater, groundwater biogeochemistry in aquifers fed by river-bank infiltration is likely to depend on large-scale climatic forcing and will be affected by climate change.” Figura, S., D. M. Livingstone, E. Hoehn, and R. Kipfer (2011), Geophys. Res. Lett., 38, L23401, doi:10.1029/2011GL049749.

Carbon dioxide emissions from global wind power deployment

Environmental implications of large-scale adoption of wind power: a scenario-based life cycle assessment – Arvesen & Hertwich (2011) “We investigate the potential environmental impacts of a large-scale adoption of wind power to meet up to 22% of the world’s growing electricity demand. The analysis builds on life cycle assessments of generic onshore and offshore wind farms, meant to represent average conditions for global deployment of wind power. We scale unit-based findings to estimate aggregated emissions of building, operating and decommissioning wind farms toward 2050, taking into account changes in the electricity mix in manufacturing. The energy scenarios investigated are the International Energy Agency’s BLUE scenarios. We estimate 1.7–2.6 Gt CO₂-eq climate change, 2.1–3.2 Mt N-eq marine eutrophication, 9.2–14 Mt NMVOC photochemical oxidant formation, and 9.5–15 Mt SO₂-eq terrestrial acidification impact category indicators due to global wind power in 2007–50. Assuming lifetimes 5 yr longer than reference, the total climate change indicator values are reduced by 8%. In the BLUE Map scenario, construction of new capacity contributes 64%, and repowering of existing capacity 38%, to total cumulative greenhouse gas emissions. The total emissions of wind electricity range between 4% and 14% of the direct emissions of the replaced fossil-fueled power plants. For all impact categories, the indirect emissions of displaced fossil power are larger than the total emissions caused by wind power.” Anders Arvesen and Edgar G Hertwich 2011 Environ. Res. Lett. 6 045102 doi:10.1088/1748-9326/6/4/045102. [Full text]

In low crop yield years biofuel production might emit more GHGs than fossil fuel burning

The significance of nitrous oxide emission due to cropping of grain for biofuel production: a Swedish perspective – Klemedtsson & Smith (2011) “The current regulations governing production of biofuels in the European Union require that they have to mitigate climate change, by producing >35% less greenhouse gases (GHG) than fossil fuels. There is a risk that this may not be achievable, since land use for crop production inevitably emits the potent GHG nitrous oxide (N₂O), due to nitrogen fertilisation and cycling in the environment. We analyse first-generation biofuel production on agricultural land and conclude that efficient agricultural crop production resulting in a good harvest and low N₂O emission can fulfil the EU standard, and is possible under certain conditions for the Swedish agricultural and bioethanol production systems. However, in years having low crop yields, and where cropping is on organic soils, total GHG emissions per unit of fuel produced can be even higher than those released by burning of fossil fuels. In general, the N₂O emission size in Sweden and elsewhere in northern Europe is such that there is a >50% chance that the 35% saving requirement will not be met. Thus ecosystem N₂O emissions have to be convincingly assessed. Here we compare Swedish emission data with values estimated by means of statistical models and by a global, top-down, approach; the measurements and the predictions often show higher values that would fail to meet the EU standard and thus prevent biofuel production development.” Kasimir Klemedtsson, Å. and Smith, K. A., Biogeosciences, 8, 3581-3591, doi:10.5194/bg-8-3581-2011, 2011. [Full text]

Attribution of climate change is not limited to model simulations

Patterns of change: whose fingerprint is seen in global warming? – Hegerl et al. (2011) “Attributing observed climate change to causes is challenging. This letter communicates the physical arguments used in attribution, and the statistical methods applied to explore to what extent different possible causes can be used to explain the recent climate records. The methods use fingerprints of climate change that are identified on the basis of the physics governing our climate system, and through the use of climate model experiments. These fingerprints characterize the geographical and vertical pattern of the expected changes caused by external influences, for example, greenhouse gas increases and changes in solar radiation, taking also into account how these forcings and their effects vary over time. These time–space fingerprints can be used to discriminate between observed climate changes caused by different external factors. Attribution assessments necessarily take the natural variability of the climate system into account as well, evaluating whether an observed change can be explained in terms of this internal variability alone, and estimating the contribution of this source of variability to the observed change. Hence the assessment that a large part of the observed recent warming is anthropogenic is based on a rigorous quantitative analysis of these joint drivers and their effects, and proceeds through a much more comprehensive and layered analysis than a comparison at face value of model simulations with observations.” Gabriele Hegerl et al 2011 Environ. Res. Lett. 6 044025 doi:10.1088/1748-9326/6/4/044025. [Full text]

Soil maximum freeze depth has decreased in Eurasian high latitudes

An observational 71-year history of seasonally frozen ground changes in the Eurasian high latitudes – Frauenfeld & Zhang (2011) “In recent decades, significant changes have occurred in high-latitude areas, particularly to the cryosphere. Sea ice extent and thickness have declined. In land areas, glaciers and ice sheets are experiencing negative mass balance changes, and there is substantial regional snow cover variability. Subsurface changes are also occurring in northern soils. This study focuses on these changes in the soil thermal regime, specifically the seasonally frozen ground region of Eurasia. We use a database of soil temperatures at 423 stations and estimate the maximum annual soil freezing depth at the 387 sites located on seasonally frozen ground. Evaluating seasonal freeze depth at these sites for 1930–2000 reveals a statistically significant trend of −4.5 cm/decade and a net change of −31.9 cm. Interdecadal variability is also evident such that there was no trend until the late 1960s, after which seasonal freeze depths decreased significantly until the early 1990s. From that point forward, likely through at least 2008, no change is evident. These changes in the soil thermal regime are most closely linked with the freezing index, but also mean annual air temperatures and snow depth. Antecedent conditions from the previous warm season do not appear to play a large role in affecting the subsequent cold season’s seasonal freeze depths. The strong decrease in seasonal freeze depths during the 1970s to 1990s was likely the result of strong atmospheric forcing from the North Atlantic Oscillation during that time period.” Oliver W Frauenfeld and Tingjun Zhang 2011 Environ. Res. Lett. 6 044024 doi:10.1088/1748-9326/6/4/044024. [Full text]

Analysis of tree-ring divergence problem

Who is the new sheriff in town regulating boreal forest growth? – Williams et al. (2011) Without abstract – here’s the first paragraph: “Climate change appears to be altering boreal forests. One recently observed symptom of these changes has been an apparent weakening of the positive relationship between high-latitude boreal tree growth and temperature at some sites (D’Arrigo et al 2008). This phenomenon is referred to as the ‘divergence problem’ or ‘divergence effect’ and is thought to reflect a non-linear relationship between temperature and tree growth, where recent warming has allowed other factors besides growing-season temperature to emerge as dominant regulators of annual growth rates.” A Park Williams et al 2011 Environ. Res. Lett. 6 041004 doi:10.1088/1748-9326/6/4/041004. [Full text available in the abstract page]

Climate change threatens turtle species

On the brink of extinction? How climate change may affect global Chelonian species richness and distribution – Ihlow et al. (2011) “Anthropogenic global climate change has already led to alterations in biodiversity patterns by directly and indirectly affecting species distributions. It has been suggested that poikilothermic animals, including reptiles, will be particularly affected by global change and large-scale reptile declines have already been observed. Currently, half of the world′s freshwater turtles and tortoises are considered threatened with extinction and climate change may exacerbate these declines. In this study, we assess how global chelonian species richness will change in the near future. We use species distribution models developed under current climate conditions for 78% of all extant species and project them onto different Intergovernmental Panel on Climate Change (IPCC) climate change scenarios for 2080. We detect a strong dependence of temperature shaping most species ranges, which coincide with their general temperature related physiological traits (i.e. temperature dependent sex determination). Furthermore, the extent and distribution of the current bioclimatic niches of most chelonians may change remarkably in the near future, likely leading to a substantial decrease of local species abundance and ultimately a reduction in species richness. Future climatic changes may cause the ranges of 86% of the species to contract and of these ranges nearly 12% are predicted to be situated completely outside their currently realized niches. Hence, the interplay of increasing habitat fragmentation and loss due to climatic stress may result in a serious threat for several chelonian species.” Flora Ihlow, Johannes Dambach, Jan O. Engler, Morris Flecks, Timo Hartmann, Sven Nekum, Hossein Rajaei, Dennis Rödder, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02623.x.

Study estimates 0.7% of global methane emissions comes from West Siberia mires

Regional methane emission from West Siberia mire landscapes – Glagolev et al. (2011) “Methane emissions from mires in all climate–vegetation zones of West Siberia (forest steppe, subtaiga, south taiga, middle taiga, north taiga, forest tundra and tundra) were measured using a static chamber method. The observed fluxes varied considerably from small negative values in forested bogs and palsa to hundreds of mgC m ^{− 2} h ^{− 1} in ponds and wet hollows. Observed data were consolidated in the form of the empirical model of methane emissions designated as the ‘standard model’. The model is based on medians of CH₄ flux distributions of eight different micro-landscape types depending on their location and estimated duration of methane emission period within the climate–vegetation zone. The current version (Bc8) of the ‘standard model’ estimates methane flux from West Siberia mires at 2.93 ± 0.97 TgC CH₄ yr ^{− 1} that accounts for about 2.4% of the total methane emission from all mires or 0.7% of global methane emission from all sources.” M Glagolev et al 2011 Environ. Res. Lett. 6 045214 doi:10.1088/1748-9326/6/4/045214. [Full text]

Removing short term variability from global temperature analysis makes years 2009 and 2010 warmest

Global temperature evolution 1979–2010 – Foster & Rahmstorf (2011) “We analyze five prominent time series of global temperature (over land and ocean) for their common time interval since 1979: three surface temperature records (from NASA/GISS, NOAA/NCDC and HadCRU) and two lower-troposphere (LT) temperature records based on satellite microwave sensors (from RSS and UAH). All five series show consistent global warming trends ranging from 0.014 to 0.018 K yr⁻¹. When the data are adjusted to remove the estimated impact of known factors on short-term temperature variations (El Niño/southern oscillation, volcanic aerosols and solar variability), the global warming signal becomes even more evident as noise is reduced. Lower-troposphere temperature responds more strongly to El Niño/southern oscillation and to volcanic forcing than surface temperature data. The adjusted data show warming at very similar rates to the unadjusted data, with smaller probable errors, and the warming rate is steady over the whole time interval. In all adjusted series, the two hottest years are 2009 and 2010.” Grant Foster and Stefan Rahmstorf 2011 Environ. Res. Lett. 6 044022 doi:10.1088/1748-9326/6/4/044022. [Full text]

Health costs of climate change in Europe are expected to be billions of euros

Projection of economic impacts of climate change in sectors of Europe based on bottom up analysis: human health – Watkiss & Hunt (2011) “This paper scopes a number of the health impacts of climate change in Europe (EU-27) quantitatively, using physical and monetary metrics. Temperature-related mortality effects, salmonellosis and coastal flooding-induced mental health impacts resulting from climate change are isolated from the effects of socio-economic change for the 2011–2040 and 2071–2100 time periods. The temperature-induced mortality effects of climate change include both positive and negative effects, for winter (cold) and summer (heat) effects, respectively, and have welfare costs (and benefits) of up to 100 billion Euro annually by the later time-period, though these are unevenly distributed across countries. The role of uncertainty in quantifying these effects is explored through sensitivity analysis on key parameters. This investigates climate model output, climate scenario, impact function, the existence and extent of acclimatisation, and the choice of physical and monetary metrics. While all of these lead to major differences in reported results, acclimatisation is particularly important in determining the size of the health impacts, and could influence the scale and form of public adaptation at the EU and national level. The welfare costs for salmonellosis from climate change are estimated at potentially several hundred million Euro annually by the period 2071–2100. Finally, a scoping assessment of the health costs of climate change from coastal flooding, focusing on mental health problems such as depression, are estimated at up to 1.5 billion Euro annually by the period 2071–2100.” Paul Watkiss and Alistair Hunt, Climatic Change, DOI: 10.1007/s10584-011-0342-z.

Global and Planetary Change is publishing a special issue on medieval climate

Climate in medieval time: How anomalous? – Diaz (2011) “The climate of the MWP/MCA has been a topic of scholarly research and debate for some 50 years (Diaz et al., in press). There is little doubt that sustained climatic anomalies on regional to hemispheric and global scales have had pronounced impacts on human society, and as events of the past few decades have shown, recent climatic extremes continue to affect humans regardless of their socioeconomic level. The publication of this special issue is meant to enhance the pool of knowledge about this period and hopefully contribute toward future advances.” Henry F. Diaz, Global and Planetary Change, doi:10.1016/j.gloplacha.2011.10.014.

Tropical high clouds react to surface warming as expected from theories

The observed sensitivity of high clouds to mean surface temperature anomalies in the Tropics – Zelinka & Hartmann (2011) “Cloud feedback represents the source of largest diversity in projections of future warming. Observational constraints on both the sign and magnitude of the feedback are limited, since it is unclear how the natural variability that can be observed is related to secular climate change, and analyses have rarely been focused on testable physical theories for how clouds should respond to climate change. In this study we use observations from a suite of satellite instruments to assess the sensitivity of tropical high clouds to interannual tropical mean surface temperature anomalies. We relate cloud changes to a physical governing mechanism that is sensitive to the vertical structure of warming. Specifically, we demonstrate that the mean and interannual variability in both the altitude and fractional coverage of tropical high clouds as measured by CloudSat, MODIS, AIRS, and ISCCP are well-diagnosed by upper tropospheric convergence computed from the mass and energy budget of the clear-sky atmosphere. Observed high clouds rise approximately isothermally in accordance with theory and exhibit an overall reduction in coverage when the Tropics warms, similar to their behavior in global warming simulations. Such cloud changes cause absorbed solar radiation to increase more than does outgoing longwave radiation, resulting in a positive but statistically insignificant net high cloud feedback in response to ENSO. The results suggest that the convergence metric based on simple mass and energy budget constraints may be a powerful tool for understanding observed and modeled high cloud behavior and for evaluating the realism of modeled high cloud changes in response to a variety of forcings.” Zelinka, M. D. and D. L. Hartmann (2011), J. Geophys. Res., doi:10.1029/2011JD016459, in press.

Oxygen content of global ocean is decreasing

Observed decreases in oxygen content of the global ocean – Helm et al. (2011) “Comparing the high-quality oxygen climatology from the World Ocean Circulation Experiment to earlier data we reveal near-global decreases in oxygen levels in the upper ocean between the 1970s and the 1990s. This globally averaged oxygen decrease is -0.93{plus minus}0.23 μmol l-1, which is equivalent to annual oxygen losses of -0.55{plus minus}0.13×1014 mol yr-1 (100-1000 m). The strongest decreases in oxygen occur in the mid-latitudes of both hemispheres, near regions where there is strong water renewal and exchange between the ocean interior and surface waters. Approximately 15% of global oxygen decrease can be explained by a warmer mixed-layer reducing the capacity of water to store oxygen, while the remainder is consistent with an overall decrease in the exchange between surface waters and the ocean interior. Here we suggest that this reduction in water mass renewal rates on a global scale is a consequence of increased stratification caused by warmer surface waters. These observations support climate model simulations of oxygen change under global warming scenarios.” Helm, K. P., N. L. Bindoff, and J. A. Church (2011), Geophys. Res. Lett., doi:10.1029/2011GL049513, in press.

Melting ice reveals artefacts of ancient reindeer hunting in southern Norway

The climatic significance of artefacts related to prehistoric reindeer hunting exposed at melting ice patches in southern Norway – Nesje et al. (2011) “The main aim of this study is to describe consequences of climate change in the mountain region of southern Norway with respect to recently exposed finds of archaeological remains associated with reindeer hunting and trapping at and around ice patches in central southern Norway. In the early years of the twenty-first century, warm summers caused negative glacier mass balance and significant glacier retreat and melting of ice patches in central southern Norway. As a result, prehistoric remains lost and/or left by past reindeer hunters appeared at ice patches in mountain areas of southern Norway. In the warm summer and autumn of 2006 the number of artefact recoveries at ice patches increased significantly because of melting of snow and ice patches and more than 100 objects were recovered in the Oppland county alone. In 2009, detailed multidisciplinary investigations were carried out at the Juvfonne ice patch in Jotunheimen at an elevation of c. 1850 metres. A well-preserved Iron Age hunting station was discovered and in total c. 600 artefacts have been documented at the Juvfonne site alone. Most of the objects were recovered and brought to the Museum of Cultural History at the University of Oslo for conservation, exhibition and storing. Thirteen so called ‘scaring sticks’ recovered from the recently exposed foreland of Juvfonne were radiocarbon dated, yielding ages that group in two separate time intervals, AD 246–534 and AD 804–898 (±1 sigma). By putting the temporal distribution of the radiocarbon-dated artefacts into the context of late-Holocene glacier-size variations in the Jotunheimen and Jostedalsbreen regions, we conclude that the most extensive reindeer hunting and trapping associated with snow/ice patches was related to periods with prevailing warm summers when the reindeer herds gathered on high-altitude, contracted glaciers and ice patches to avoid insect plagues. The ‘freshness’ of the fragile organic finds strongly indicates that at least some of the artefacts were rapidly covered by snow and ice and that they may have been more-or-less continuously covered by snow and ice since they were first buried.” Atle Nesje, Lars Holger Pilø, Espen Finstad, Brit Solli, Vivian Wangen, Rune Strand Ødegård, Ketil Isaksen, Eivind N. Støren, Dag Inge Bakke, Liss M Andreassen, The Holocene November 30, 2011 0959683611425552, doi: 10.1177/0959683611425552.

Climate record shows several abrupt cooling events during early Holocene in North America

Abrupt cooling repeatedly punctuated early-Holocene climate in eastern North America – Hou et al. (2011) “Climate proxy records and general circulation models suggest that Atlantic Meridional Overturning Circulation (AMOC) plays a key role for global climate changes. Paleoceanographic data document multiple episodes of prominent AMOC weakening during the early Holocene. However, proxy records at adjacent continents have not been demonstrated to fully capture the climate responses to multiple AMOC variation due to temporal resolution and/or the proxy sensitivity. Here we present decadal- to multidecadal-resolution hydrogen isotopic records of aquatic biomarkers from Blood Pond, Massachusetts during the early Holocene. Our data reveal a full series of prominent and abrupt cooling events centered on 10.6, 10.2, 9.5, 9.2, 8.8 and 8.4 ka. These abrupt climatic reversals coincide with key intervals of weakened AMOC, suggesting an apparent relationship between AMOC oscillations and the abrupt continental climate changes in northeastern North America. The noticeable connection implies that the AMOC variation did play an important role in the abrupt climate changes during the early Holocene. Our data also suggest that northeastern North America may experience significant climatic variations should the predicted major disturbance of AMOC occur in the coming century as a result of anthropogenic greenhouse gas emissions.” Juzhi Hou, Yongsong Huang, Bryan N Shuman, W Wyatt Oswald, David R Foster, The Holocene November 30, 2011 0959683611427329, doi: 10.1177/0959683611427329.

Why AMOC had already slowed down when Heinrich events started?

Heinrich event 1: an example of dynamical ice-sheet reaction to oceanic changes – Álvarez-Solas et al. (2011) “Heinrich events, identified as enhanced ice-rafted detritus (IRD) in North Atlantic deep sea sediments (Heinrich, 1988; Hemming, 2004) have classically been attributed to Laurentide ice-sheet (LIS) instabilities (MacAyeal, 1993; Calov et al., 2002; Hulbe et al., 2004) and assumed to lead to important disruptions of the Atlantic meridional overturning circulation (AMOC) and North Atlantic deep water (NADW) formation. However, recent paleoclimate data have revealed that most of these events probably occurred after the AMOC had already slowed down or/and NADW largely collapsed, within about a thousand years (Hall et al., 2006; Hemming, 2004; Jonkers et al., 2010; Roche et al., 2004), implying that the initial AMOC reduction could not have been caused by the Heinrich events themselves. Here we propose an alternative driving mechanism, specifically for Heinrich event 1 (H1; 18 to 15 ka BP), by which North Atlantic ocean circulation changes are found to have strong impacts on LIS dynamics. By combining simulations with a coupled climate model and a three-dimensional ice sheet model, our study illustrates how reduced NADW and AMOC weakening lead to a subsurface warming in the Nordic and Labrador Seas resulting in rapid melting of the Hudson Strait and Labrador ice shelves. Lack of buttressing by the ice shelves implies a substantial ice-stream acceleration, enhanced ice-discharge and sea level rise, with peak values 500–1500 yr after the initial AMOC reduction. Our scenario modifies the previous paradigm of H1 by solving the paradox of its occurrence during a cold surface period, and highlights the importance of taking into account the effects of oceanic circulation on ice-sheets dynamics in order to elucidate the triggering mechanism of Heinrich events.” Álvarez-Solas, J., Montoya, M., Ritz, C., Ramstein, G., Charbit, S., Dumas, C., Nisancioglu, K., Dokken, T., and Ganopolski, A., Clim. Past, 7, 1297-1306, doi:10.5194/cp-7-1297-2011, 2011. [Full text]

Water-related stresses from climate change threaten endangered plant species

Climate change threatens endangered plant species by stronger and interacting water-related stresses – Bartholomeus et al. (2011) “Atmospheric CO₂-concentration, temperature and rainfall variability are all expected to increase in the near future. The resulting increased dynamics of soil moisture contents, together with increased plant physiological demands for both oxygen and water, will lead to an increased occurrence of wet and dry extremes of plant stresses, i.e. of oxygen and drought stress, respectively, alone and in interaction. The use of indirect environmental variables of previous studies and their focus on one stress at a time has hampered understanding the causal impact of climate change on plant species composition through changes in abiotic site conditions. Here, we use process-based simulations of oxygen and drought stress and show that both stresses will increase (on average with ca. 20% at sites where both stresses occur) in a warmer and more variable future (2050) climate (applying a national downscaled version of IPCC scenarios). These stresses will increasingly coincide, i.e. both stresses will occur more often (but not at the same time) within the same vegetation plot. We further show that particularly this increased coincidence of water-related stresses will negatively affect the future occurrence of currently endangered plant species (a reduction of 16%), while such a decrease is not apparent for common species. Individual stresses did not affect the occurrence of endangered plant species. Consequently, the species that are already threatened under the current climate, will suffer most from climate change.” Bartholomeus, R. P., F. Witte, P. M. van Bodegom, J.C. Van Dam, and R. Aerts (2011), J. Geophys. Res., doi:10.1029/2011JG001693, in press.

Drought-induced tree mortality has increased in Canada’s boreal forests

A drought-induced pervasive increase in tree mortality across Canada’s boreal forests – Peng et al. (2011) “Drought-induced tree mortality is expected to increase worldwide under projected future climate changes. The Canadian boreal forests, which occupy about 30% of the boreal forests worldwide and 77% of Canada’s total forested land, play a critical role in the albedo of Earth’s surface and in its global carbon budget. Many of the previously reported regional-scale impacts of drought on tree mortality have affected low- and middle-latitude tropical regions and the temperate forests of the western United States, but no study has examined high-latitude boreal regions with multiple species at a regional scale using long-term forest permanent sampling plots. Here, we estimated tree mortality in natural stands throughout Canada’s boreal forests using data from the permanent sampling plots and statistical models. We found that tree mortality rates increased by an overall average of 4.7% yr⁻¹ from 1963 to 2008, with higher mortality rate increases in western regions than in eastern regions (about 4.9 and 1.9% yr⁻¹, respectively). The water stress created by regional drought may be the dominant contributor to these widespread increases in tree mortality rates across tree species, sizes, elevations, longitudes and latitudes. Western Canada seems to have been more sensitive to drought than eastern Canada.” Changhui Peng, Zhihai Ma, Xiangdong Lei, Qiuan Zhu, Huai Chen, Weifeng Wang, Shirong Liu, Weizhong Li, Xiuqin Fang & Xiaolu Zhou, Nature Climate Change 1,467–471(2011)doi:10.1038/nclimate1293.

Snowfall to total winter precipitation ratio has decreased in Poland

Long-term variability of occurrence of precipitation forms in winter in Kraków, Poland – Twardosz et al. (2011) “The paper discusses long-term change in snowfall, rainfall and mixed precipitation viewed in conjunction with air temperature and North Atlantic Oscillation (NAO) in winter (December–February). In the study of contemporary climate change and its effect on the hydrological cycle it is useful to focus on winter precipitation forms. A 146-year secular observation series from Kraków, spanning the period 1863–2008, was used to extract data on the number of days with precipitation and on precipitation amount broken down by form. Statistically significant trends were found in total and mixed precipitation, but not in snowfall and rainfall. The climate warming effect has contributed to a material decrease in the snowfall to total winter precipitation ratio during the second half of the 20th c. The highest impact of air temperature was found in the wintertime variation in number of days with snowfall while the NAO had a significant influence on the frequency and amount of both rainfall and snowfall.” Robert Twardosz, Ewa Łupikasza, Tadeusz Niedźwiedź and Adam Walanus, Climatic Change, DOI: 10.1007/s10584-011-0352-x. [Full text]