VIENNA, Austria - Glaciers will all but disappear from the Alps by 2050, scientists warned yesterday, basing their bleak outlook on mounting evidence of slow but steady melting of the continental ice sheets.
In western Austria's Alpine province of Tyrol, glaciers have been shrinking by about 3 percent a year, meaning their mass decreases annually by roughly 3 feet, said Roland Psenner of the University of Innsbruck's Institute for Ecology.
He said the year 2050 was a conservative estimate; if the glaciers continued melting at the current rate, most could vanish by 2037.
"The future looks rather liquid," Psenner said.
Experts at a regional conference on the Alps, held annually in the mountain resort of Alpbach, stopped short of blaming global warming. But they called for a review of preventive measures to protect people living in valleys at risk of dangerous flooding.
Runoff from melting glaciers caused severe flooding that devastated parts of Switzerland in the summer of 2005.
Glacial melting is a global problem, according to the Zurich-based World Glacier Monitoring Service, which keeps tabs on 30 ice sheets in nine mountain ranges worldwide and says their average mass is steadily eroding.
Glaciers are the planet's largest source of fresh water after polar ice, which scientists say also is melting to 100-year lows. In Europe, they are also hugely popular with skiers and snowboarders seeking year-round thrills, and help anchor a multimillion-dollar tourist industry.
In 2005, glacier thickness decreased by an average of 231/2 inches, and in 2004 by an average of 271/2 inches, the Swiss agency said, citing preliminary measurements.
Since 1980, it said, Europe's glaciers have lost about 311/2 feet of ice. About 7 feet melted away in a single summer - 2003 - when a heat wave zapped much of Europe, said Michael Zemp, a glacier expert at the University of Zurich.
"What's important for a glacier is winter snow accumulation and a cold summer with not a lot of melting," Zemp said in a telephone interview yesterday. "A bad year for a glacier is a dry winter and a hot summer, and these are the conditions we've been seeing."
"Glaciers have been in a general retreat worldwide since the end of the last Ice Age," he said.
Forecasting their demise is problematic, he said: "This isn't a weather forecast. But we are seeing an accelerated glacial melting."
In the 13 years spanning 1991 to 2004, twice as much glacial ice melted away in Europe than in the 30 preceding years, climatologists say.
To be sure, a few glaciers have more staying power: Switzerland's Great Aletsch Glacier is still more than a half-mile thick, and seems destined to survive well into the 22d century.
But data collected by aircraft and satellites since 2002 has shown that many of Earth's estimated 160,000 glaciers, from the Rocky Mountains to the Himalayas, have been shrinking.
Scientists say the phenomenon has been occurring for more than a century, suggesting that man-made emissions of carbon dioxide are combining with purely natural factors, such as a shift in jet streams pumping warmer air into traditionally cooler northern climes.
But Europeans have fretted and sweated their way through an unusually balmy winter that has shattered temperature records and forced World Cup ski organizers to cancel competitions for lack of snow.
"Winter has been in a holding pattern," said Gerhard Baumgartner, a meteorologist with Austria's weather service.
Besides what President Bush says about climate change in tonight's State of the Union address, global warming may be in the news for weeks, thanks to an expected report.
What it is: Phase one of the Intergovernmental Panelon Climate Change.
Who wrote it: This segment's 1,600 pages were written by more than 600 scientists, reviewed by an additional 600 experts, and edited by officials from 154 countries.
What it will say: Human-caused global warming is here - visible in the air, water and melting ice - and is destined to get much worse in the future. Expect lots of numbers.
Quote: "The smoking gun is definitely lying on the table," said top U.S. climate scientist Jerry Mahlman, who reviewed this entire segment. "The evidence . . . is compelling."
What it's based on: Already published peer-review science.
When it will be released: The 12-page summary for policymakers will be edited in secret word-by-word by government officials for several days next week and released to the public on Feb. 2. The remainder of that first report from scientists will come out months later.
When the rest of it will be released: Phase two - to be released in April - will for the first time discuss how global warming is already changing health, species, engineering and food production. The full report will be issued in four phases over the year, as was the case with the last report, issued in 2001.
Intergovernmental Panel on Climate Change: www.ipcc.ch
World Glacier Monitoring Service: www.geo.unizh.ch/wgms