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 (16 feet). In 2007 the UN Intergovernmental Panel for Climate Change (IPCC) predicted sea levels would rise 18 to 59 centimetres (7.2 to 23.2 inches) by 2100, but this estimate did not factor in the potential impact of crumbling icesheets in Greenland and Antarctica. Today many of the same scientist say that even if heat-trapping CO2 emissions are curtailed, the ocean watermark is more likely to go up by nearly a metre, enough to render several small island nations unlivable and damage fertile deltas home to hundreds of millions.