Glaciers are important features in climate studies. The smaller alpine glaciers respond to climatic variation in ways visible during the human lifetime. Glacial processes modify the landscape leaving signatures of past climatic conditions. The large ice sheets have an important role in the global heat and water balance, which in turn play a major role in climate change. Glaciers are an important component in the hydrological cycle, acting as reservoirs of stored water with residence times of months to millennia.