Earth has lost 12.5 trillion tons of polar ice since 1979

The main driver isn't warmer air. Five-sixths of the loss comes from warmer ocean water eroding the ice sheets from below and the sides, which the authors call bad news for future sea level rise. Lead author Ines Otosaka of Northumbria University says every additional centimetre of sea level rise exposes another 2 to 3 million people to flooding at least once a year. Greenland's Jakobshavn glacier is now retreating by up to 50 metres a day. The European Space Agency-led team previously tracked ice loss only from the 1990s using European satellite data. Adding NASA satellite records extended the picture back to 1979 for Antarctica and 1972 for Greenland.

Scientists expect the melting to keep accelerating, putting low-lying coastal regions, including much of South and Southeast Asia, at growing flood risk.