Ice and Snow

Ice and snow are important components of the Earth’s climate system and are particularly sensitive to globalwarming. Over the last few decades the amount of ice and snow, especially in the Northern Hemisphere, has decreased substantially, mainly due to human-made global warming. Changes in the volumes and extents of ice and snow have both global and local impacts on climate, ecosystems and human well-being.

Snow and the various forms of ice play different roles within the climate system. The two continental ice sheets ofAntarctica and Greenland  actively influence the global


climate over time scales of millennia to millions of years,but may also have more rapid effects on, for example, sea level. Snow and sea ice, with their large areas but relatively
small volumes, are connected to key interactions and feedbacks at global scales, including solar reflectivity  and ocean circulation. Perennially frozen ground (permafrost) influences soil water content and vegetation  over continental scale northern regions and is one of the

cryosphere components most sensitive to atmospheric warming trends. As permafrost warms, organic material  stored in permafrost may release greenhouse gases into the atmosphere and increase the rate of global warming.

Glaciers and ice caps, as well as river and lake ice, with their smaller areas and volumes, react relatively quickly  to climate effects, influencing ecosystems and human  activities on a local scale. They are good indicators of  climate change.