One of the most alarming consequences of rapid global warming would be a collapse of the west Antarctic ice sheet. Until now scientists have generally assumed that it would raise the global sea level by five to six metres, but a more detailed analysis, published in the journal Science, shows this is an overestimate.

The study, led by Jonathan Bamber, of Bristol University, found that a complete collapse would raise the sea level by an average of 3.3 metres – though the rise would not be distributed evenly around the world. The biggest impact would be along the Atlantic and Pacific coasts of north America, where levels would rise 25 per cent more than the global average.