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Kilimanjaro's snows melting, but ...
Yes, the snows of Mount Kilimanjaro are melting, but global warming isn't to blame, some scientists say.
By Sandi Doughton, McClatchy News Service
Last update: June 12, 2007 – 11:22 PM
SEATTLE
The shrinking snow cap atop Mount Kilimanjaro has become an icon of global warming. Pictures of the African peak, which has lost 90 percent of its ice cover, were featured in Al Gore's documentary, "An Inconvenient Truth." Greenpeace activists once held a satellite news conference on the summit to sway participants in an international climate conference.
But most scientists who study Kilimanjaro's glaciers have long been uneasy with the volcano's poster-child status. Yes, ice cover has shrunk by 90 percent, they say.
But no, the buildup of greenhouse gases from cars, power plants and factories is not to blame.
"Kilimanjaro is a grossly overused mis-example of the effects of climate change," said University of Washington climate scientist Philip Mote, co-author of an article in the July/August issue of American Scientist magazine.
Mote is concerned that critics will try to use the article to debunk broader climate-change trends.
He hastens to add that global warming is, indeed, responsible for the fact that nearly every other glacier around the globe is melting away. Kilimanjaro just happens to be the worst possible case study.
Rising nearly 4 miles from the plains of eastern Tanzania, the 19,340-foot Kilimanjaro has seen its glaciers decline steadily for well over a century -- since long before humans began pumping large amounts of carbon dioxide into the atmosphere, Mote points out.
Most of the world's glaciers didn't begin their precipitous declines until the 1970s, when measurable global warming first appeared.
Also, recent data show temperatures on the volcano never dip below freezing. So melting triggered by a warmer atmosphere can't be the reason the small summit ice sheet is retreating about 3 feet a year, said Georg Kaser, co-author of the article and a glaciologist at the University of Innsbruck in Austria.
Most glaciers in temperate zones, like those on Mount Rainier, extend to lower elevations where their terminus is warmed to the melting point in summer.
On Kilimanjaro, ice loss seems to be driven by two factors: a lack of snowfall and sublimation, the same process that causes freezer burn by sucking moisture out of food.
Researchers believe Kilimanjaro's glaciers formed about 11,000 years ago, when the region was undergoing a period of wet weather that allowed snow to accumulate. But even before the first Europeans reached the summit in 1889, the weather has been dry in Eastern Africa. There simply hasn't been enough snowfall to keep up with the loss of ice due to sublimation, Kaser explained.
Sublimation, caused by exposure to sunlight and dry air, occurs when ice essentially skips the melting step and evaporates.
Kaser, who climbs Kilimanjaro twice a year to gather data, says the ice topography shows little evidence that melting is anything but a minor force. Jagged spires and cliffs made of ice up to 120 feet tall are not softened around the edges.
Even though the mountain presents an interesting scientific puzzle, it's an anomaly compared with what's happening with other glaciers, said Douglas Hardy, a paleoclimatologist at the University of Massachusetts. The new article will be seized on by "global warming naysayers" and could give people the mistaken impression that it calls global warming into question, Hardy predicted.
"What value to society does that serve?" he asked.
© 2007 Star Tribune. All rights reserved.
2007-06-16
03:04:40
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