Human activity has already had a large impact on many permafrost areas through the creation of thermokarst. Although humans have as yet had little direct influence on the state of glaciers, ice shelves and ice sheets, the situation will change in the future as a consequence of global warming. Three main consequences of warming may be discerned for ice sheets: ice temperature rise and attendant ice flow changes; enhanced basal melting beneath ice shelves and related dynamical response; and changes in mass balance. The state of Greenland and Antarctica is discussed. Many of the world’s valley glaciers have retreated as a consequence of the climatic changes, especially warming, that have occurred in the last hundred or so years since the ending of ‘The Little Ice Age’. Glaciers that calve into water can show especially fast rates of retreat, with rates greater than 1 km per year being possible. Globally the average annual mass loss of glaciers during the warming decade from 1996 to 2005 was twice that of the previous decade (1986-1995) and over four times that of the decade from 1976-1985. Many mountainous areas are predicted to see the disappearance, thinning or retreat of glaciers in coming decades.