The world's glaciers react to and interact with changes in global and regional climates. 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 . The present volume of the Earth's glacier ice, if totally melted, represents about 80 meters in sea-level rise. For example, during the last glacial peak, about 20,000 years ago, sea level is estimated to have been 120 meters lower than it is today.
White areas show ice sheets and other glaciers around the world.
The white spots in the oceans are islands where glaciers are found. A thorough global baseline study of the areal extent of existing glaciers is required if we are going to assess the magnitude of changes in glaciers that will occur worldwide during the 21st century. This research comprises a comprehensive global baseline study of the total area of glacier ice on Earth. The effort is important because present and future changes in glacier margins worldwide cannot be assessed without such a baseline study. The atlas also includes ancillary information from historical and modern ground observations by glaciologists.