Without ice to reflect sunlight, the Arctic Ocean would warm more quickly, resulting in the release of greenhouse gases stored in the Arctic permafrost soils. These soils contain twice as much carbon as is in the atmosphere.

Mr Summerkorn said that the warming of the Arctic surface waters would accelerate the melting of the Greenland ice sheet, speeding up the sea level rise. “This could lead to flooding affecting one quarter of the world’s population and extreme global weather changes,” he said.

The East Antarctic ice sheet has been losing mass for the last three years, according to an analysis of data from a gravity-measuring satellite mission.

... West Antarctic and Greenland ice sheets are losing mass.

These two bodies of ice contain enough water to raise sea levels by about six to seven metres (20ft) each if they melted completely.

Melting the East Antarctic sheet would raise sea levels by much more - about 50-60m.

But scientists have generally discounted the possibility of it happening because the region is so cold.