Snow decline on Mount Kilimanjaro is not due to climate change, scientists claim today.
The retreat of ice caps on the African mountain has been held up by some as evidence of global warming's effect on the world.
Writing in the American Scientist magazine, two researchers argue that this is an inaccurate view.
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There is no evidence to support that assertion. It's not that it is impossible, but rather the decline is
most likely associated with processes dominated by sublimation and with an energy balance dominated by solar radiation, rather than by a warmer troposphere," said climatologist Dr Philip Mote, a University of Washington research scientist.
"There are dozens, if not hundreds, of photos of midlatitude glaciers you could show where there is absolutely no question that they are declining in response to the warming atmosphere."
But Kilimanjaro lies in the tropics where there are different processes at work than those that have diminished glacial ice in regions closer to the Earth's poles, the researchers – Dr Mote and Georg Kaser, a glaciologist at the University of Innsbruck in Austria – write.
They add that the decline in the Tanzanian mountain's ice has been happening for more than 100 years, with the majority occurring before 1953. But evidence of global warming before 1970 has been inconclusive.
Instead, they propose that the decline is due to interacting factors including the vertical shape of the ice's head, which allows it to shrink but not expand, and decreased snowfall.
Fluctuating weather patterns related to the Indian Ocean could also affect the ice, the scientists add.
A rough survey in 1889 suggested that Kilimanjaro's ice cap was about 12.5 square miles. In 2003 it was little more than 1.5 square miles.
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