Climate models indicate that global warming will be felt most acutely at high latitudes, especially in the Arctic where reductions in sea ice and snow cover are expected to lead to the greatest relative temperature increases. Ice & snow cool the climate by reflecting solar energy back to space, so a reduction in their extent would lead to greater warming in the region.

Many changes already are apparent in high-latitude regions.

For example:
Satellite data suggest that the extent of snow cover has declined by 10 percent since the late 1960s. During the 20th century, annual duration of lake and river ice cover in the mid- and high latitudes of the northern hemisphere declined by about two weeks. Since the 1950s, the extent of northern hemisphere spring and summer sea-ice decreased by about 10-15 percent. Researchers have measured a decline of roughly 40 percent in the thickness of Arctic sea-ice during late summer and early autumn during the past several decades. (1)

Pine Island Glacier, part of the West Antarctic Ice Sheet, thinned by up to 1.6 m (5.2 feet) per year between 1992 and 1999. (2)

(1)   IPCC. 2001. Summary for Policymakers, IPCC WGI Third Assessment Report. Geneva
(2)   Shepherd, Andrew, Duncan J. Wingham, Justin A. D. Mansley, and Hugh F. J. Corr. 2001. Inland thinning of Pine Island Glacier, West Antarctica. Science 291 (5505):862-864.

Report in the Los Angeles Times in June 2002:
Alaska's terrain is cracking under the stress of global warming that has produced an average 3.8 degree Celsius rise in temperature statewide during the past 30 years. Many residents in the state have resorted to using hydraulic jacks to keep their houses from collapsing as foundations, once braced by permafrost, begin to buckle. Forests in the north appear to be drowning as melting permafrost forces up water in a phenomenon native Alaskans have termed "trunken trees"

Swiss Revue Juni 2007:
Swiss glaciers have lost 50 % of their volumne between 1850 and 1970 and until 2000 have lost even more. By 2050 it is estimated only 25 % of the original glaciers will have survived.

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