July 19, 2006 — The summer ice and famed glaciers of the European Alps will likely be gone by the end of the century, Swiss climate modelers confirm.
The change reflects similar warming trends seen in the already glacier-free U.S. Rockies and Sierra Nevada of California.
The primary cause of the demise of Europe’s once-enduring zones of perpetual winter is the ongoing rise in summertime temperatures linked to global warming. The loss of the glaciers dramatically affects not only summer water supplies, which in many places depend on glacial melt water, but also tourism in the Alps.
"People come traveling here to see white mountains, not black mountains," said climate modeler Michael Zemp of the University of Zurich in Switzerland.
Zemp and his colleagues gathered all the data they could find, producing an unprecedented high-resolution model of changes in the European Alps. They calibrated the model by using it to reproduce decades of changes from the 1800s to 2000. Then they ran the model into the future to see what’s likely to happen next.
From 1850 to the 1970s, records show the area covered by Alpine glaciers shrank by 35 percent, Zemp and his colleagues report in the current issue of Geophysical Research Letters.
That shrinkage accelerated, hitting 50 percent by 2000. If the summertime temperatures rise another nine degrees Fahrenheit, the Alps would become completely ice free, even if winter snowfall increases, according to the model.
Even a more modest five-degree rise by the end of the century would leave only 10 percent of the glacier area, they report.
Like most other climate models, the one used by Zemp and his team divides the study area into a grid. Inside each cube, various equations simulate the real-world changes. For most models, those grids are tens of miles on a side.
The new European Alps model, however, has grids just 100 meters by 100 meters. This scale has enabled the researchers to not only model individual mountains and valleys, but to break down specific changes that could happen in different countries bordering on the Alps.
This makes it possible to examine changes to water supply. Right now many valleys coming out of the Alps are surging with glacial melt water while others, below places where ice is already gone, are drying up, said Zemp.
"Without glaciers, the rivers were dry," he said.
"That’s really scary because it’s very difficult to recover that sort of (ice) mass," says ice and climate researcher Thomas Painter of the National Snow and Ice Data Center in Colorado. In the U.S. portion of the Rockies, most of the glaciers are long gone, and never played a significant role in water supplies, he explained.
Still, global warming is changing the water cycle, affecting the timing of water that cascades down from the Rockies and California’s Sierra Nevada — mountain ranges that supply water to great swaths of the western U.S.
The two things that are being watched, besides changing weather patterns, are the elevations where rainfall freezes into snow and where and when that snow melts or evaporates, said Painter.
"It’s kind of a tangled web," he added.
"The whole issue of how climate affects water supply is a huge issue," said geographer and water supply researcher Kurt Cuffey of the University of California at Berkeley.
California gets essentially all its precipitation in the winter. The summertime melting snow high in the Sierra Nevada has been California’s summer and autumn water supply for generations. Its name is Spanish for "Snowy Range."
Global warming is expected to raise the elevation of snowfall and cause snow to begin melting earlier in the spring. That could leave California with water shortages every summer in coming decades, Cuffey explained.
"The state doesn’t have the reservoir capacity," said Cuffey. That’s why officials in the U.S.’s most populous state are already looking at getting more water from other sources, including desalinization of ocean water, he said.
Of course, the severity of the water and glacier problems depends largely on how much the climate warms. And that, said Zemp, "depends on the actions and decisions by governments" to fight global warming.
