Comparisons of satellite images, aerial photos, and old surveys of Alpine glaciers indicate that the ice masses are losing area at an accelerating rate.
Between 1973 and 1999, the total area covered by almost 940 Swiss glaciers fell by 18 percent, an average rate of 1.3 percent per year. That tempo is more than six times the annual rate of shrinkage that those ice masses experienced from 1850 to 1973, says Frank Paul of the University of Zurich-Irchel in Zurich.
Small glaciers suffered disproportionate losses in recent years, he notes. More than 44 percent of the area lost between 1973 and 1999 occurred on glaciers with areas less than 1 square kilometer, even though those ice masses accounted for only 18 percent of the glaciers studied. Paul and his colleagues report their findings in the Nov. 16, 2004 Geophysical Research Letters.
When the researchers extrapolated those melting trends to the 5,400-or-so glaciers found throughout the Alps, the results suggested that ice covered 675 km2 less area in 1999 than it did about a quarter-century earlier.
At current rates of retreat, all Alpine glaciers below an altitude of 2,000 meters will disappear by 2070.