Snow occurs predominantly on the northern continents, on the sea ice of the Arctic Ocean and on Antarctica. On the Northern Hemisphere continents, snow covers a maximum mean area of 45.2 million km2, typically in January. The minimum snow-cover extent usually occurs in August and covers a mean area of 1.9 million km2, most of which is snow on the Greenland ice sheet and on mountain glaciers. As a result, snow cover is the surface characteristic responsible for the largest annual and inter annual differences in surface reflectivity (albedo) in the Northern Hemisphere.
From collection: Global Outlook for Ice and Snow
Hugo Ahlenius, UNEP/GRID-Arendal