Editing IPCC:AR6/WGI/TS (section)

===== TS.4.3.2.8 Polar =====

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'''It is ''virtually certain'' that surface warming in the Arctic will continue to be more pronounced than the global average warming over the 21st century. An intensification of the polar water cycle will increase mean precipitation, with precipitation intensity becoming stronger and more ''likely'' to be rainfall rather than snowfall ( ''high confidence'' ). Permafrost warming, loss of seasonal snow cover, and glacier melt will be widespread ( ''high confidence'' ). There is ''high confidence'' that both the Greenland and Antarctic ice sheets have lost mass since 1992 and will continue to lose mass throughout this century under all emissions scenarios. Relative sea level and coastal flooding are projected to increase in areas other than regions with substantial land uplift ( ''medium confidence'' ). Links to chapters 2.3, 3.4, 4.3, 4.5, 7.4, 8.2, 8.4, Box 8.2, 9.5, 12.4.9, Atlas.11.1, Atlas.11.2'''
In addition to the main changes summarized above and in Section TS.4.3.1, further details are given below.

'''Heat and cold:''' Changes in Antarctica showed larger spatial variability, with ''very likely'' warming in the Antarctic Peninsula since the 1950s and no overall trend in East Antarctica. Less warming and weaker polar amplification are projected as ''very likely'' over the Antarctic than in the Arctic, with a weak polar amplification projected as ''very likely'' by the end of the 21st century. Links to chapters 4.3.1, 4.5.1, 7.4.4, 12.4.9.1, Atlas.11.1, Atlas.11.2

'''Wet and dry:''' Recent decades have seen a general decrease in Arctic aridity ( ''high confidence'' ), with increased moisture transport leading to higher precipitation, humidity and streamflow and a corresponding decrease in dry days. Antarctic precipitation showed a positive trend during the 20th century. The water cycle is projected to intensify in both polar regions, leading to higher precipitation totals (and a shift to more heavy precipitation) and higher fraction of precipitation falling as rain. In the Arctic, this will result in higher river flood potential and earlier meltwater flooding, altering seasonal characteristics of flooding ( ''high confidence'' ). A lengthening of the fire season ( ''medium confidence'' ) and encroachment of fire regimes into tundra regions ( ''high confidence'' ) are projected. Links to chapters 8.2.3, 8.4.1, Box 8.2, 9.4.1, 9.4.2, 12.4.9.2, Atlas.11.1, Atlas.11.2

'''Wind:''' There is ''medium confidence'' in mean wind decrease over the Russian Arctic and Arctic North-East North America, but ''low confidence'' of changes in other Arctic regions and Antarctica. Links to chapters 12.4.9.3

'''Snow and ice:''' Reductions in spring snow cover extent have occurred across the Northern Hemisphere since at least 1978 ( ''very high confidence'' ). Permafrost warming and thawing have been widespread in the Arctic since the 1980s ( ''high confidence'' ), causing strong heterogeneity in surface conditions. There is ''high confidence'' in future glacier- and ice-sheet loss, permafrost warming, decreasing permafrost extent and decreasing seasonal duration and extent of snow cover in the Arctic. Decline in seasonal sea ice coverage along the majority of the Arctic coastline in recent decades is projected to continue, contributing to an increase in coastal hazards (including open water storm surge, coastal erosion and flooding). Links to chapters 2.3.2, 3.4.2, 3.4.3, 9.4.1, 9.4.2, 9.5, 12.4.6, 12.4.9, Atlas.11.2

'''Coastal and oceanic:''' Higher sea levels contribute to ''high confidence'' for projected increases of Arctic coastal flooding and higher coastal erosion (aided by sea ice loss) ( ''medium confidence'' ), with lower confidence for those regions with substantial land uplift (Arctic North-East North America and Greenland). Links to chapters 12.4.9.5

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