research highlights

METHANE EMISSIONS examined –conflict relationships using scanning electron microscopy. They Controls on with, for the first time, a geographically found severe levels of shell dissolution in the Glob. Change Biol. http://doi.org/jw8 (2012) disaggregated approach. Using a conflict undersaturated samples. database that contains 16,359 individual These findings in live pteropods in their from the Arctic have geo-located violent events for East Africa natural environment validate laboratory based the potential to provide a strong positive from 1990–2009, they considered a wide studies that showed the potential vulnerability feedback to the , enhancing range of socio-economic, geographic and of L. helicina antarctica to . the degree of climate warming. However, the political factors at a 1° gridded resolution. Furthermore, this study demonstrates that main physical and environmental controls Unlike earlier studies, they found that — ocean acidification is already having an on remain unclear. after controlling for the non-geographic impact — ahead of many aragonite-saturation This knowledge gap fundamentally limits the factors — precipitation levels that are two projections — indicating that regional accuracy of predictions of methane emissions standard deviations above the long-term declines in pteropod populations may occur and ultimately the extent of average decrease the risk of violence by 30.3%, sooner than previously predicted. AB that can be expected in the Arctic. whereas drier and normal periods have no In an effort to distil the state-of-the- effect. Results also show that temperatures PALEOCLIMATE art in Arctic methane emissions research, two standard deviations higher than the Reconstructing temperature David Olefeldt, from the Department of average raise the risk of violence to 29.6%, Geophys. Res. Lett. http://doi.org/jw9 (2012) Integrative Biology, University of Guelph, with normal and cooler temperatures not Canada, and co-workers performed a affecting incidence of violence. MC synthesis of 65 studies involving over 300 Arctic sites where data on environmental and OCEAN ACIDIFICATION physical variables — including Aragonite shell damage conditions — were available. Nature Geosci. 5, 881–885 (2012) Their findings indicate that future changes in terrestrial high-latitude methane Ocean models predict that the confluence emissions will be more closely related to of natural (deepwater ventilation) and changes in moisture, soil temperature and anthropogenic (ocean acidification) factors vegetation composition than to the direct may cause the upper layers of the Southern effects of permafrost thaw on organic Ocean to become undersaturated in matter availability. AB aragonite — a form of calcium carbonate — by 2050. Such undersaturation is likely to HUMAN IMPACTS affect aragonite-shelled organisms, which Climate–conflict nexus can dominate surface water communities in © ISTOCKPHOTO/THINKSTOCK Proc. Natl Acad. Sci. 109, 18344–18349 (2012) polar regions and constitute an important component of the oceanic system. The global surface temperature timeseries — Previous studies have shown a positive Nina Bednaršek, from the British which is thermometer based — provides impact of climatic variability on the risk Antarctic Survey, Cambridge, UK, and key evidence for global warming. However, of conflict in sub-Saharan Africa, with co-workers sampled from surface waters uncertainties associated with this record are temperature as the strongest driver of with low aragonite-saturation levels large, and it also suffers from limitations in violence. However, the lack of thorough (ΩA ~ 1) in the Southern Ocean, and temporal and spatial coverage. geographical considerations challenges compared the shell structure of a pteropod A new Paleo Index has been compiled those results. (Limacina helicina antarctica) — a by David Morrill Anderson, of the National John O’Loughlin of the University of of planktonic mollusc — with specimens Ocean and Atmospheric Administration’s Colorado, Boulder, USA, and colleagues from aragonite-supersaturated regions National Climate Data Center, USA, and colleagues. The index was derived from ATMOSPHERIC SCIENCE 173 temperature-sensitive timeseries including: corals, ice cores, speleothems Stilling air Environ. Res. Lett. 7, 044034 (2012) (mineral deposits in caves), lake and ocean sediments and historical documents. Ozone and particulate matter can accumulate in still atmospheric conditions and lead It extends back to 1730, with a global to harmful air quality. Climate change is altering global atmospheric circulation and distribution. The Index shows a significant precipitation patterns, which regulate the frequency of air stagnation. upward trend for 1880–1995, as well as Daniel Horton, of Stanford University USA, and co-workers used a multimodel ensemble accelerated warming after 1980. of global climate models to investigate the response of the National Climatic Data Center Comparing the Paleo Index with global air-stagnation index to global warming, up to the end of this century. Their results show surface temperature shows similar small-scale the highly industrialized and highly populated regions of the eastern United States, trends, providing independent evidence of the Mediterranean Europe and eastern China have atmospheric conditions that are particularly warming observed. These findings support vulnerable to global warming and increased stagnation of air. the thermometer data, increasing confidence Air quality is an area of concern as health can be greatly affected. This study shows in the accuracy of the global surface that air quality could be affected by changing atmospheric conditions as a result of global temperature timeseries. BW warming. Further work is necessary to quantify the impacts of global warming on air quality, and the consequences for health. BW Written by Alastair Brown, Monica Contestabile and Bronwyn Wake.

NATURE CLIMATE CHANGE | VOL 3 | JANUARY 2013 | www.nature.com/natureclimatechange 15

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