In Peru, the Quelccaya icecap in the southern Andes has shrunk by 20 per cent since 1963.
Scientists have found that the rate of retreat of one of the main glaciers running out of the icecap, the Qori Kalis, was more than 30 times greater in the past three years than between 1963 and 1978.
The melting ice has formed a large lake which did not exist in 1983 but now covers about 4ha, 1.5ha bigger than in 1998. Bare earth has been exposed for the first time in thousands of years.
Professor Thompson presented findings from 20 years of studies by his research team, which surveyed tropical icecaps and ice-cores from South America, Africa, China and Tibet, at the annual meeting of the American Association for the Advancement of Science in San Francisco.
By analysing the isotopes of oxygen in the ice, the scientists can estimate the temperature at the time the snow fell.
From this they discovered that for the ice-cores of the Tibetan plateau, the past 50 years have been the warmest in history.
Professor Thompson said: "We have long predicted that the first signs of changes caused by global warming would appear at the few fragile, high-altitude icecaps and glaciers in the tropics.
"These findings confirm those predictions."
The melting glaciers are not only an ecological catastrophe, they also threaten local economies. About four-fifths of the icecap on Kilimanjaro has disappeared in the past 80 years, jeopardising the tourist trade.
"At this rate, all the ice will be gone between 2010 and 2020," said Professor Thompson. "And that's probably a conservative estimate."
The melting of the Quelccaya icecap of Peru will be even more devastating.
"The loss of these frozen reservoirs threaten water resources for hydroelectric power production in the region, and for crop irrigation and municipal water supplies.
"What we're doing is cashing in on a bank account that was built over thousands of years but isn't being replenished."
Professor Thompson said his research suggested that the snowline, the point on tropical mountains where water is permanently frozen, was climbing higher and higher.
"If you look at the earth as a whole, glaciers are retreating everywhere except in Norway." He suggested that the Norwegian glaciers were advancing because of increased snowfall, which could be due to global warming.
- HERALD CORRESPONDENT
Herald Online feature: Climate change
Intergovernmental Panel on Climate Change
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Summary: Climate Change 2001
United Nations Environment Program
World Meteorological Organisation
Framework Convention on Climate Change
