A “warm, crazy” winter has left sea ice in the Arctic at its lowest levels on record for the season, scientists said.

The huge West Antarctic ice sheet is undergoing a glacially slow but unstoppable collapse, new studies show, and scientists say that means a bigger rise in sea level than previously thought.

Arctic Sea ice melted this summer to the second lowest level since record-keeping began more than 50 years ago, scientists reported today, mostly blaming global warming.

New satellite observations show that sea ice in the Arctic is melting faster while air temperatures in the region are rising sharply, scientists say.