Global warming is causing trillions of dollars of damage to coral reefs, aggravating risks to tropical small island states threatened by rising sea levels, a U.N. report said on Thursday. The rise in sea levels off some islands in the Western Pacific was four times the global average, with gains of 1.2 cms (0.5 inch) a year from 1993 to 2012, due to shifts in winds and currents, said the United Nations' Environment Programme (UNEP). The study, released to mark the U.N.'s World Environment Day on June 5, said a warming of waters from the Indian Ocean to the Caribbean was damaging reefs by killing the tiny animals that form corals with their stony skeletons. true "These 52 nations, home to over 62 million people, emit less than one per cent of global greenhouse gases, yet they suffer disproportionately from the climate change that global emissions cause," said Achim Steiner, head of UNEP. "Some islands could become uninhabitable and others are faced w