At a seminar on glaciers in Oslo on Friday, experts said the consequences of fast-melting glaciers could be catastrophic, with low lying areas from Bangladesh to the Netherlands getting swamped.
"It's too early to say if glacier melting is accelerating worldwide," said Jeffrey Kargel of the US Geological Survey. "In some areas it is, but the picture is mixed".
Many glaciers are apparently melting because of rising temperatures – glaciers in the Alps have shrunk by more than 20% in the past two decades.
"In the Alps the rate is definitely accelerating," said Andreas Kaab of the University of Zurich.
Around the Arctic, many glaciers in Canada and parts of Alaska are also retreating faster than in the past. But some in Norway have even grown while others in Alaska are stable.
One reason for glacier growth may be that rising temperatures melt sea ice that is sucked up into clouds as moisture, some of which falls as snow, causing some of the ice mountains to grow.
The Briksdalsbreen glacier in west Norway, for instance, grew about 400 metres in the late 1990s before a recent retreat.
"An accelerated melting has been observed in parts of the Arctic – Canada and Alaska," said John Ove Hagen, a glacier expert at the University of Oslo. "But it's not the same around the Arctic".
UN studies project that emissions of greenhouse gases, from cars, power plants and factories, may drive up global temperatures by 1.4 to 5.8 Celsius by 2100.
That will contribute to melting glaciers, with UN studies indicating that sea levels could rise by about 30-50cms by 2100, threatening many coastal regions and low-lying islands such as Tuvalu in the Pacific.
But the studies indicate that the main stores of frozen water on land, in Antarctica and Greenland, are unlikely to melt much in the coming century – their vast volumes of ice acting as a deep freezer.