Glaciers for which there is long-term data are shrinking at record rates and many could disappear within decades, the U.N. Environment Program said Sunday.
Scientists measuring the health of almost 30 glaciers around the world found that ice loss reached record levels in 2006, the U.N. agency said.
UNEP warned that further ice loss could have dramatic consequences particularly in India, whose rivers are fed by Himalayan glaciers.
The west coast of North America, which gets much of its water from glaciers in mountain ranges such as the Rockies and Sierra Nevada, also would be affected, it said.
"There are many canaries emerging in the climate change coal mine," UNEP's executive director Achim Steiner said in a statement. "The glaciers are perhaps among those making the most noise and it is absolutely essential that everyone sits up and takes notice."
He urged governments to agree stricter targets for emissions reductions at an international meeting next year in the Danish capital, Copenhagen.
On average, the glaciers shrank by 4.9 feet in 2006, the most recent year for which data are available.
The most severe loss was recorded at Norway's Breidalblikkbrea glacier, which shrank 10.2 feet in 2006, while Chile's Echaurren Norte glacier was the only one to grow slightly thicker.
"The latest figures are part of what appears to be an accelerating trend with no apparent end in sight," said Wilfried Haeberli, director of the World Glacier Monitoring Service.
"This continues the trend in accelerated ice loss during the past two and a half decades and brings the total loss since 1980 at more than 10.5 m (meters)," or about 30 feet, the service said in a statement.
The Zurich-based body conducted the study on which the findings are based.
Haeberli said glaciers lost an average of about a foot of ice a year between 1980 and 1999. But since the turn of the millennium the average loss has increased to about 20 inches.
The 30 glaciers tracked by the service are those that have the longest record of measurements, dating back to 1980.