Accelerated ice melt in west Antarctica is inevitable for the rest of the century no matter how much carbon emissions are cut, research indicates. The implications for sea level rise are “dire,” scientists say, and mean some coastal cities may have to be abandoned. From a report: The ice sheet of west Antarctica would push up the oceans by 5 metres if lost completely. Previous studies have suggested it is doomed to collapse over the course of centuries, but the new study shows that even drastic emissions cuts in the coming decades will not slow the melting. The analysis shows the rate of melting of the floating ice shelves in the Amundsen Sea will be three times faster this century compared with the previous century, even if the world meets the most ambitious Paris agreement target of keeping global heating below 1.5C above pre-industrial levels.

Losing the floating ice shelves means the glacial ice sheets on land are freed to slide more rapidly into the ocean. Many millions of people live in coastal cities that are vulnerable to sea level rise, from New York to Mumbai to Shanghai, and more than a third of the global population lives within 62 miles (100km) of the coast. The climate crisis is driving sea level rise by the melting of ice sheets and glaciers and the thermal expansion of sea water. The biggest uncertainty in future sea level rise is what will happen in Antarctica, the scientists say, making planning to adapt to the rise very hard. Researchers said translation of the new findings on ice melting into specific estimates of sea level rise was urgently needed.