A slightly fresher lake, III

The arctic: Ice-free in the summer by 2040. Unlike previous estimates, this model takes in to account the effect of warm ocean currents traveling further north than usual, helping to break up the ice even more than general warming.

Researchers assessing the impact of carbon emissions on the world’s climate have calculated that late summer in the Arctic will be ice-free by 2040 or earlier - well within a lifetime.

Some ice would still be found on coastlines, notably Greenland and Ellesmere Island, but the rest of the Arctic Ocean, including the pole, would be open water.

The Nasa-funded US team of researchers said the ice retreat is likely to remain fairly constant until 2024 when there will be a sudden speeding up of the process....

Their finding may, however, already be out of date and something of an over-optimistic forecast, said Professor Chris Rapley, head of the British Antarctic Survey....

"The study findings may be an under estimate of when the Arctic summer ice might be all gone," he said. "It could well be their assumptions are more optimistic than they might be."