Water Resources Division, U.S. Geological Survey 1994 The world's glaciers react to and interact with changes in global and regional climates. Most mountain glaciers worldwide have been retreating since the latter part of the 19th century; global sea level has risen about 10 centimeters during the past century. Glaciers vary in size as a result of several factors, of which climate variation is probably the most important. The reasons we are interested in glacier variation include its connection to climate change and to global sea level. application/pdf 10.3133/fs00994 en U.S. Geological Survey Satellite image atlas of glaciers of the world reports