Larsen, J.N., O.A. Anisimov, A. Constable, A.B. Hollowed, N. Maynard, P. Prestrud, T.D. Prowse, and J.M.R. Stone. 2014. Polar Regions.

Several recent climate impact assessments on polar regions have been undertaken, including the synthesis report on Snow, Water, Ice and Permafrost in the Arctic (AMAP, 2011a), the State of the Arctic Coast 2010 (2011) reports, the Antarctic Climate and the Environment (Turner et al., 2009, 2013), Arctic Resilience Interim Report 2013 (2013), and the findings of the International Polar Year (IPY; Krupnick et al., 2011). These reports draw a consistent pattern of climate-driven environmental, societal, and economic changes in the polar regions in recent decades. In this chapter, we use the scientific literature, including these reports, to consolidate the assessment of the impacts of climate change on polar regions from 2007, advance new scientific evidence of impacts, and identify key gaps in knowledge on current and future impacts. Previous IPCC reports define the Arctic as the area within the Arctic Circle (66ºN), and the Antarctic as the continent with surrounding Southern Ocean south of the polar front, which is generally close to 58ºS (IPCC, 2007). For the purpose of this report we use the conventional IPCC definitions as a basis, while incorporating a degree of flexibility when describing the polar regions in relation to particular subjects. Changes in the physical and chemical environments of the polar regions are detailed in the WGI contribution to the AR5. There is evidence that Arctic land surface temperatures have warmed substantially since themid-20th century, and the future rate of warming is expected to exceed the global rate. Sea ice extent at the summer minimum has decreased significantly in recent decades, and the Arctic Ocean is projected to become nearly ice free in summer within this century. The duration of snow cover extent and snow depth are decreasing in North America while increasing in Eurasia. Since the late 1970s, permafrost temperatures have increased between 0.5°C and 2°C. In the Southern Hemisphere, the strongest rates of atmospheric warming are occurring in the western Antarctic Peninsula (WAP, between 0.2°C and 0.3°C per decade) and the islands of the Scotia Arc, where there have also been increases in oceanic temperatures and large regional decreases in winter sea ice extent and duration.