Observations of snow-covered area for the Northern Hemisphere show a significant development in the later 20th century, with a reduction of the area covered by snow in the spring (March-April) from some 38 million km2 in the 1930s to today's 35 million km2. Snow represents an important resource for water, ecosystems and human activities, as well as for reflecting incoming sun light. The linear trend shows a decrease in snow-covered area of 2.7 ± 1.5 _ 106 km2 or 7.5 ± 3.5 %. The shaded fields in the figure represents the 5 to 95% range of the data.
From collection: Global Outlook for Ice and Snow
Hugo Ahlenius, UNEP/GRID-Arendal