These are the conclusions of numerical modeling experiments by scientists from the University of Zurich, Switzerland. The study will be published 15 July in Geophysical Research Letters, a journal of the American Geophysical Union.

Scientists consider glaciers to be among the best natural indicators of climate change and, therefore, monitor them closely. Rapidly shrinking glacier areas, spectacular tongue retreats, and increasing mass losses are clear signs of the atmospheric warming observed in the Alps during the last 150 years.

Michael Zemp and colleagues in the Department of Geography of the University of Zurich note that in the 1970s, about 5,150 Alpine glaciers covered a total area of 2,909 square kilometers [1,123 square miles].

This represented a loss of about 35 percent of glacial area from 1850 to that time. Accelerated loss of ice cover since then has resulted in a total loss of 50 percent of the 1850 area, culminating in a volume loss of 5 to 10 percent of the remaining ice during the extraordinary warm year of 2003.

According to the Intergovernmental Panel on Climate Change (IPCC), an increase in summer air temperature of one to five degrees Celsius [two to nine degrees Fahrenheit] and a precipitation change between minus-20 percent and plus-30 percent by the end of the 21st century is a plausible scenario.

The University of Zurich researchers say that for each one degree Celsius [two degrees Fahrenheit] increase in mean summer temperature, precipitation would have to increase by 25 percent to offset the glacial loss.

"Our study shows that under such scenarios, the majority of Alpine glaciers might disappear within the coming decades", says glaciologist Zemp, lead author of the study. With an increase in summer temperature of more than three degree Celsius [five degrees Fahrenheit], only the largest glaciers, such as the Great Aletsch Glacier [in Switzerland], and those on the highest mountain peaks could survive into the 22nd century.

"Especially in densely populated high mountain areas such as the European Alps, one should start immediately to consider the consequences of such extreme glacier wasting on the hydrological cycles, water management, tourism, and natural hazards," he says.

The study was funded by the European Union, through the Swiss Federal Office of Education and Science.

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