Glaciers are melting worldwide due to climate change. Satellite images provide visible evidence of retreat when comparing images from different time periods. Alpine glaciers have lost around half of their total area between 1850 and 2000. Nearly 60% of glaciers in Spain have already melted, leaving only 21 glaciers remaining in the Pyrenees. Studies from the 1950s predicted that rising carbon dioxide levels from human activity could cause significant melting of ice sheets and rising sea levels. A 4 degree rise in temperature was predicted to eliminate nearly all the world's glaciers. Glacial retreat has impacts such as reducing the reliability of ski areas. Mitigation and adaptation strategies are needed to address the effects of climate change.