According to a new study, the East Antarctic icesheet, once seen as largely unaffected by global warming, has lost billions of tonnes of ice since 2006 and could boost sea levels in the future.Published in Nature Geoscience, the study shows that the smaller but less stable West Antarctic icesheet is also shedding significant mass. Scientists worry that rising global temperatures could trigger a rapid disintegration of West Antarctica, which holds enough frozen water to push up the global ocean watermark by about five metres.In 2007 the UN Intergovernmental Panel for Climate Change predicted sea levels would rise 18 to 59 centimetres by 2100, but this estimate did not factor in the potential impact of crumbling icesheets in Greenland and Antarctica. More than 190 nations gather in Copenhagen next month to hammer out a global climate deal to curb greenhouse gases and help poor countries cope with its consequences.