Kate Ravilious writes:

Over the next eighty years global warming is set to melt enough ice from the Greenland Ice Sheet to reverse 4000 years of cumulative ice growth – with rates of ice-loss more than quadruple even the fastest melt rates during the past 12,000 years. These stark conclusions come from new simulations which, for the first time, put current and projected future rates of ice-loss into context; comparing them directly with historical rates of ice-loss. These latest results are consistent with previous research that shows that if we continue our current high trajectory of greenhouse gas emissions we can expect Greenland to become ice-free in as little as 1000 years.

A couple of weeks ago a massive chunk of ice – equivalent in size to the Caribbean island of Montserrat – broke away from north-east Greenland. It serves as yet another indicator of the rapid pace of change in this region, with rising temperatures currently driving ice-loss at a rate of around 6100 billion tonnes per century. But how unprecedented is this? How quickly did the Greenland Ice Sheet melt during warm periods in the past?

The Greenland Ice Sheet currently stretches across 1,710,000 square kilometres and geologists have used ice-core data to understand how it has waxed and waned in the past. Until now, however, no-one had compared how ice-sheet activity in the past matched up with what scientists expect to see in the future. Jason Briner, from the University at Buffalo in New York, and colleagues have made use of recent reconstructions of climate and ice-sheet thickness to simulate the evolution of a portion of ice-sheet in southwestern Greenland, running their simulations from 12,000 years ago, through to eighty years into the future. [Continue reading…]