Alpine glaciers could all but disappear within this century
University of Zurich, unicom, American Geophysical Union
Zurich, 10. Juli 2006
WASHINGTON The European Alps could lose some 80 percent of their glacier cover by the end of this century, if summer air temperatures rise by three degrees Celsius [five degrees Fahrenheit]. And if temperatures increase by five degrees Celsius [nine degrees Fahrenheit], the Alps would become almost completely ice-free by 2100. 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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Alpine glaciers to disappear within decades?
Michael Zemp, Wilfried Haeberli, Martin Hoelzle, Frank Paul: Glaciology and Geomorphodynamics Group, Department of Geography, University of Zurich, Zurich, Switzerland.
Zemp, M., W. Haeberli, M. Hoelzle, and F. Paul (2006), Alpine glaciers to disappear within decades?, Geophys. Res. Lett., 33, L13504, doi:10.1029/2006GL026319.
Contact information for authors:
Michael Zemp: +41-44-635 51 39 or firstname.lastname@example.org
Wilfried Haeberli: +41-44-635 51 20 or email@example.com
Martin Hoelzle: firstname.lastname@example.org
Frank Paul: email@example.com
This press release is available in German: http://www.geo.unizh.ch/~mzemp/press/pressrelease_zemp_de.htm
Please note that the provided five explanatory figures are not all part of the GRL paper.
Fig. 1: Alpine glacier cover in 1850, 1975 and 2000. Glaciers in the European Alps lost about 35% of their overall area from 1850 until the 1970s. In 2000 only about half of the Alpine ice cover of 1850 was left. This corresponds to a loss rate of about 3% per decade between 1850 and 1975 and of almost 9% per decade between 1975 and 2000.
Fig. 2: Synthetic oblique perspective of the Rhone Glacier with historical glacier extents and modelled accumulation areas of the reference period (197190) and for a climate scenario. The oblique perspective was generated from a digital elevation model (SRTM3) overlaid with a satellite scene (SPOT-2, HRV pan) of September 17, 1992. The glacier extents of 1850 (white) and 1973 (red) are shown as glacier outlines. The modelled climatic accumulation area (cAA) of the reference period (197190; red) is overlaid with the modelled climatic accumulation area (blue) for a climate scenario with 3 °C warmer summer temperature and 10% more annual precipitation. As a consequence, the tongue of the Rhone Glacier (which is nourished on ice from the accumulation area) will strongly retreat.
Fig. 3: Modelled Alpine ice cover (climatic accumulation area) according to an increase in summer air temperature of +1 to +5 °C and/or changes in annual precipitation. The total of 100% refers to the ice cover of the reference period (197190). The dotted line refers to pure temperature increase, whereas the other lines represent combined temperature and precipitation changes. Reading example: A rise in summer temperature of 3 °C combined with an increase in annual precipitation of 10% would reduce the Alpine ice cover to 27% of the glaciated area of the reference period (197190).
Fig. 4: Modelled remains of the Alpine glacierisation (climatic accumulation area) according to an increase in summer air temperature of +1 to +5 °C. The total of 100% refers to the ice cover of the reference period (197190). The 100%-marks of the other lines refer to the fraction of glacierisation of the corresponding Alpine country. Reading example: A rise in summer air temperature of 3 °C would reduce the Alpine ice cover (red curve) to about 20% of the glacier cover of the reference period (197190). The corresponding glacier remains of Switzerland (blue, dashed line) amounts to about 30%, whereas in Austria (black, dashed line) only about 7% of the glacier cover of the reference period is left.
Fig. 5: Modelled remains of Swiss glaciers (climatic accumulation area) according to an increase in summer air temperature of +1 to +5 °C. The total of 100% refers to the ice cover of the reference period (197190). The 100%-marks of the other lines refer to the fraction of the Swiss glacierisation of the corresponding Swiss canton.
last update: 10.07.2006