Evidence of Recent Changes in Global Snow and Ice Cover

Data on recent variations in the seasonal extent of snow cover and sea ice, of the terminal position and volume of alpine glaciers, and of ground temperature profiles in permafrost areas are reviewed. The extent of seasonal snow cover and of sea ice has fluctuated irregularly over the last 15— 20 years. There is no apparent response to global warming trends. In contrast, most glaciers retreated and thinned from the late 19th century until the 1960s and Alaskan permafrost temperatures have risen 2°–4° C per century. Recently, some glacier advances have been noted.