London: The world's glaciers and ice caps are now in terminal decline because of global warming, scientists have found.

survey has revealed that across the world the melt rate has sharply accelerated in recent years, placing even previously stable glaciers in jeopardy.

The loss of glaciers in South America and Asia will threaten the water supplies of millions of people within a few decades, the experts warn.

Georg Kaser, a glaciologist at the University of Innsbruck, Austria, who led the research, said: "The glaciers are going to melt and melt until they are all gone. There are not any glaciers getting bigger any more."

Loss of land-based ice is one of the clearest signals of global temperature rise, and the state of glaciers has become a key argument in the debate over climate change. Last year, New Scientist published a letter from the U.K. botanist David Bellamy, a renowned climate sceptic, which claimed that 555 of 625 glaciers measured by the World Glacier Monitoring Service have been growing since 1980.

Claim discredited

His claim was quickly discredited, but the perception that glaciers are both growing and shrinking remains.Dr. Kaser said that "99.99 per cent of all glaciers" were now shrinking.

Increased winter snowfall meant that a few, most notably in New Zealand and Norway, got bigger during the 1990s, he said, but a succession of very warm summers since then had reversed the trend.

His team combined different sets of measurements, which used stakes and holes drilled into the ice to record the change in mass of more than 300 glaciers since the 1940s. They extrapolated these results to cover thousands of smaller and remote glaciers not directly surveyed.

The results revealed that the world's glaciers and ice caps — defined as all land-based ice except the mighty Greenland and West Antarctic ice sheets — grew steadily until about 1970, when they began to shrink.

The rate of shrinking increased significantly in 2001. On average, the world's glaciers and ice caps lost enough water between 1961 and 1990 to raise global sea levels by 0.35 mm to 0.4 mm each year. For 2001-2004, the figure rose to 0.8 mm to 1mm each year.

Dr. Kaser said it was unclear why the glaciers grew from 1940 to 1970, but speculated it was because increased air pollution blocked sunlight — a phenomenon known as global dimming. Writing in the journal Geophysical Research Letters, the scientists say: "Late 20th century glacier wastage is essentially a response to post-1970 global warming."

Strong evidence

Dr. Kaser said: "There is very, very strong evidence that this is down to human-caused changes in the atmosphere."

Emissions of greenhouse gases such as carbon dioxide trap heat in the atmosphere, warming the surface. One of the first impacts of glacier melting is likely to be in South America.

In August, a report from 20 U.K.-based environment and development groups warned that Andean glaciers are melting so fast that some are expected to disappear within 15 to 25 years.

This will deny major cities water supplies and put populations and food supplies at risk in Colombia, Peru, Chile, Venezuela, Ecuador, Argentina and Bolivia.

Other countries, including India, are noticing the effects. Studies show snow and ice cover in the eastern Himalayas has shrunk by about 30 per cent since the 1970s. Melting glaciers have created lakes in the mountains, which could burst and cause widespread flooding.

Of 150 glaciers that once stood in Glacier National Park in the northern U.S., only 27 remain.

The U.S. Environmental Protection Agency says the biggest are a third the size they were in 1850. Continued warming could melt them completely by 2030.

© Guardian Newspapers Limited 2006

Printer friendly page  
Send this article to Friends by E-Mail