Arctic ice melting faster than expected

The study, published in the latest edition of the journal Geophysical Research Letters, found that the actual rate at which summer sea ice had shrunk per decade during the past 50 years was more than three times faster than an average of 18 of the most highly regarded climate simulations.

Retreating Arctic ice is considered a key indicator of the pace of global warming by environmentalists, and one that could have devastating knock-on repercussions for the wider climate, including warmer oceans and rising sea levels.

Declining ice levels also poses a threat to Arctic wildlife including polar bears, walruses and ringed seals.

According to the Intergovernmental Panel on Climate Change, which releases the third of three reports into the causes, consequences and mitigation of global warming in Thailand this week, the Arctic could be ice-free in summer by the latter part of the 21st century.

But the research, conducted by the U.S.-based National Center for Atmospheric Research (NCAR) and the University of Colorado's National Snow and Ice Data Center (NSIDC), demonstrates that the 18 models on which the IPCC has based its current recommendations could already be out of date -- and that the retreat of the ice could already be 30 years ahead of the IPCC's worst case scenario.

"This suggests that current model projections may in fact provide a conservative estimate of future Arctic change, and that the summer Arctic sea ice may disappear considerably earlier than IPCC projections," said NSIDC's Julienne Stroeve who led the study.