Worldwide glacier retreat

One of the most visually compelling examples of recent climate change is the retreat of glaciers in mountain regions. In the U.S. this is perhaps most famously observed in Glacier National Park, where the terminus of glaciers have retreated by several kilometers in the past century, and could be gone before the next century (see e.g. the USGS web site, here, and here). In Europe, where there is abundant historical information (in the form of paintings, photographs, as well as more formal record-keeping), retreat has been virtually monotonic since the mid 19th century (see e.g. images of the glaciers at Chamonix). These changes are extremely well documented, and no serious person questions that they demonstrate long term warming of climate in these regions. New work published in Science (“Extracting a Climate Signal from 169 Glacier Records”) highlights these results, and uses them to make a new estimate of global temperature history since about 1600 A.D., which agrees rather well with previous, independent temperature reconstructions.

Of course, as we frequently remind readers on this site, changes in one particular region do not necessarily translate to worldwide trends. That is why the work of such groups of scientists as the World Glacier Monitoring Service, which compiles observations on changes in mass, volume, area and length of glaciers, is important. From the compilations of WGMS (and many other groups and individuals), we know that glacier retreat is in fact an essentially global phenomenon, with only a few isolated (and well understood) counter-examples, such as western Norway. The figure at right shows an example from WGMS, as published in the 2001 IPCC report. (Click on the figure for details).The photos at left show South Cascade Glacier in Washington State in 1928 and 2000.

What causes glaciers to retreat like this? With the exception of glaciers that terminate in the ocean, and glaciers in the polar regions or at extreme high altitudes where the temperature is always below freezing, essentially just two things determine whether a glacier is advancing or retreating: how much snow falls in the winter, and how warm it is during the summer.

Page 1 of 3 | Next page