The polar ice caps are melting six times faster than they were in the 1990s, the most comprehensive look at the data to date has found.That data, compiled and analyzed by the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE), puts the melting of Greenland and Antarctica's ice sheets on track with the worst-case-scenario prediction from the Intergovernmental Panel on Climate Change (IPCC). If this trend continues, it could put 400 million people at risk from sea level rise by 2100."That's not a good news story," professor Andrew Shepherd from the University of Leeds told BBC News.Shepherd helped lead an international team of 89 polar scientists who analyzed ice loss at both poles using 26 surveys and 11 satellite missions between 1992 and 2018, according to a University of Leeds press release.They found that Greenland and Antarctica together lost 6.4 trillion tonnes (approximately 7.1 trillion U.S. tons) of ice between 1992 and 2017, raising global sea levels by 17.8 millimeters (approximately .7 inches). Not only that, but the rate of loss accelerated. The ice sheets lost 81 billion tonnes (approximately 89 billion U.S. tons) a year in the 1990s and 475 billion tonnes (approximately 524 billion U.S. tons) a year in the 2010s. This means they are now contributing much more to sea level rise."Today, the ice sheets contribute about a third of all sea-level rise, whereas in the 1990s, their contribution was actually pretty small at about 5%. This has important implications for the future, for coastal flooding and erosion," Shepherd told BBC News.The Antarctica figures were published in Nature in 2018, while the Greenland figures were published in Nature this week.