The cryosphere is an important part of the global climate system and comprises those portions of the Earth’s surface where water is in its solid form, frozen into ice or snow. Elements of the cryosphere are found at all latitudes and encompass glaciers, ice caps and ice sheets as well as lake and river ice, sea ice, snow cover and frozen ground. The cryosphere is linked to its environment by many processes. It influences moisture fluxes, precipitation, hydrology, atmospheric and oceanic circulation. In particular, the high albedo of snow-covered areas has a large impact on the radiation balance. A change in extent of these areas directly affects the surface temperature of the Earth. Moreover, the components of the cryosphere store large amounts of water whereas nowadays about 99% of the global ice volume is concentrated in the ice sheets of the polar regions, in Greenland and in Antarctica. They have the potential to alter the global sea level by several meters under the influence of climate changes within the next centuries.