Up to 12 percent of Arctic ice has turned to water in the past 30 years, an alarming fact that only accelerates global warming further, the UN warned in a report on Monday.
The Arctic ice sheet has shrunk by six to seven percent in winter and by 10 to 12 percent in summer over the period, according to the Global Outlook for Ice and Snow report, published on the eve of World Environment Day.
The snow-covered regions of the northern hemisphere have reduced from seven to 10 percent during March and April in the past 30-40 years, according to the report presented by the UN Environment Programme (UNEP).
The melting of the ice and snow is not only a consequence of global warming, it is also an accelerating factor, researchers presenting the report in the Norwegian Arctic town of Tromsoe said.
"Snow and ice reflect 70 to 80 percent of the sun's energy, whereas water absorbs it. If snow and ice continue to melt, this will amplify global warming," report author Paal Prestrud told journalists.
"6.5 billion people on this planet have built their way of life... around a certain reality. This reality is changing even more rapidly than expected," UNEP executive director Achim Steiner added.
The acceleration process also makes it more difficult to anticipate future developments, he added.
"(This process) is of such magnitude that our ability to predict the future is severely constrained," Steiner told AFP.
"This means that the adaptation process of coping with climate change is potentially so far-reaching in terms of economic costs and consequences that we have to act now," he added.
For instance, an estimated 40 percent of the world's population could be affected by the loss of snow and glaciers on the mountains of Asia, according to researchers.
Many rivers of the continent, such as the Ganges, the Brahmaputra or the Mekong, begin in the Himalayas and less ice and snow would mean less water for drinking and agriculture.
In addition, rising sea levels would affect low-lying coasts and islands, something of particular concern for countries such as Bangladesh and Indonesia.
The report also feared that melting ice and snow could trigger more abrupt climatic changes, such as hurricanes and floods, with wider-ranging impacts on people, economies and wildlife.
Melting ice and snow was considered more likely to increase hazards like avalanches and floods from the build-up of potentially unstable glacial lakes.
Rising temperatures and the thawing of permafrost, or frozen land, was also triggering the expansion of existing lakes and the emergence of new lakes and rivers in places like Siberia.
"If the permafrost thaws, it will (further) amplify global warming and will change current sea levels," Prestrud said.
"Existing indigenous species would disappear because they can't leave the region. New species would come in, migrating from the south," he added.
The polar bear is for example expected to become extinct if the ice melts completely.
Some communities are already adapting to climate change. Hunters in parts of Greenland are abandoning traditional dogsleds in favour of skiffs (small open boats) as a result of less predictable sea ice.
"Snow and ice are continuing to decline because of human activity. They will continue to do so if greenhouse gases continue to be emitted," Prestrud warned.
