Kilimanjaro not a victim of climate change, UW scientist says
Seattle Times science reporter
The shrinking snowcap 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 four miles from the plains of eastern Tanzania, 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 from Kilimanjaro show temperatures on the 19,340-foot volcano never rise above 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 new 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 leftovers.
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.
Other researchers say melting may become more important if global temperatures continue to climb. Some have reported water gushing from boreholes and glacier margins. It's also possible climate change may play a role in droughts that have starved Kilimanjaro of snow, though that pattern was established before the planet began to warm significantly, Kaser said.
He was the first to point out the disconnect between global-warming rhetoric and scientific data from Kilimanjaro. His 2004 findings became fodder for conservative Web sites and global-warming skeptics — many funded by the oil and coal industries — who argued that all reports about melting glaciers are suspect.
The debate was so rancorous that a co-author of the 2004 study decided not to lend his name to the American Scientist article, which summarizes what researchers have learned about Kilimanjaro's complex ice dynamics.
Even though the mountain presents an interesting scientific puzzle, it's an anomaly compared to 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.
Mote, who as Washington's state climatologist travels the Northwest to warn of global warming's regional impacts, said he worried about the article being misused but decided to go ahead.
"Science is a process of getting to the truth," he said.
Even when the truth has unexpected twists like this: Models predict global warming will increase rainfall in Eastern Africa, which could actually be the thing that saves the "shining mountain's" snowy crown.
Sandi Doughton: 206-464-2491 or email@example.com
Information in this article, originally published June 12, was corrected June 12. A previous version of this story incorrectly stated that temperatures on the summit of Mount Kilimnajaro never dip below freezing. Actually, temperatures never rise above freezing, which is why scientists believe melting caused by global warming is not responsible for shrinkage of glaciers on the African peak.
Copyright © 2007 The Seattle Times Company