The Alps have lost about 50 per cent of their ice in the past century, and of 27 glaciers that existed in Spain in 1980, only 13 remain. The largest glacier on Mt Kenya has shrunk to 8 per cent of its size 100 years ago, while those on Mt Kilimanjaro, also in Kenya, are only a quarter as big. The huge ice rivers of the Tien Shan mountain range, on the Sino- Russian border, have lost 22 per cent of their ice volume in the past 40 years.
Professor Mark Meier, the scientist leading the research, said he was sure the changes were the result of global warming over the past century. "The rate of warming is unprecedented in the last 600 years and the retreat of glaciers is probably unprecedented too, although we do not have the figures to prove it," he said. "But I'm convinced there is a detectable human influence in the pattern of climate change.''
Although the melting was contributing slightly to sea level rises, that effect would increase over time, he said. Already, the melting was causing significant increases in the flows of some rivers, Professor Meier said.
The in-depth study by the International Panel on Climate Change (IPCC) in 1996 forecast that sea levels would rise by more than 45 centimetres (18 inches) by 2100. A third of that would come as run-off from melting glaciers and icecaps, and more than half through the thermal expansion of the oceans as they warm - another indirect, but devastating, effect of global warming.
The latest evidence comes from studies in western Europe, the US, Africa, Russia, China and New Zealand. It specifically excludes Antarctica and Greenland, which hold 94 per cent of the world's total ice mass, although other studies have shown ice shelves retreating there too.
More significantly, the water in the non-polar glaciers is recycled more quickly by run-off, evaporation and rain, so it contributes more rapidly to sea level rise than the polar ice sheets. "Regional" glaciers are also more sensitive to warming.
Professor Meier, from the geological sciences department at the University of Colorado in Boulder, collected data on hundreds of glaciers, from the estimated 200,000 worldwide.
A new analysis method was used to define the relationships of several variable characteristics of glaciers. This allowed more accurate estimation of sizes, thicknesses and volume distribution of glaciers.
Preliminary calculations showed that the Glacier National Park, in Montana, US, will have no glaciers left within a century.
The findings were reported at a meeting of the American Geophysical Union, in Boston, Massachusetts.