Ice and snow are parts of the cryosphere. The term “cryosphere” comes from the ancient Greek word for freeze or cold and collectively describes all frozen water in the Earth system. The cryosphere includes sea-, lake-, and river-ice, snow, solid precipitation, glaciers, ice caps and ice sheets, permafrost and seasonally frozen ground. The WCRP organizes the research on the role of cryosphere in climate through the CliC project, which is co-sponsored by SCAR. WCRP and SCAR are the originators of the IGOS Theme on Cryosphere, an activity aimed at systematic improvement of cryospheric observations. The WCRP research has confirmed the pivotal role in the climate system of cryospheric elements found especially, but not exclusively, in the polar regions. During the International Polar Year 2007/2008, there will be a massive effort to study the polar regions and cryosphere to which the WCRP will make a critical contribution.

The increased pace of global warming has prompted concerns about cryospheric mechanisms through which an abrupt climate change may occur: the irreversible melting of the Greenland ice cap; an ice-free Arctic Ocean during summers; a slowdown of the ocean thermohaline circulation due to increased fresh water run-off. All these topics are of interest to WCRP’s Working Group on Coupled Modelling (WGCM) and other WCRP projects such as CLIVAR. Examples of key WCRP science questions related to the cryosphere include those concerning the speed of melting of glaciers and Greenland and Antarctic ice sheets and their contribution to mean sea-level rise. The future of water resources originating from snowmelt and glaciers is now a serious challenge for many nations, and the additional release of carbon to the atmosphere associated with thawing of the permafrost has the potential of increasing the greenhouse warming.

Through its Climate and Cryosphere (CliC) Project, the WCRP facilitates research targeting these science questions.