The entire ice mass of Greenland will disappear from the world map if temperatures rise by as little as 2C, with severe consequences for the rest of the world, a panel of scientists told Congress today. Greenland shed its largest chunk of ice in nearly half a century last week, and faces an even grimmer future, according to Richard Alley, a geosciences professor at Pennsylvania State University Sometime in the next decade we may pass that tipping point which would put us warmer than temperatures that Greenland can survive," Alley told a briefing in Congress, adding that a rise in the range of 2C to 7C would mean the obliteration of Greenland's ice sheet. "What is going on in the Arctic now is the biggest and fastest thing that nature has ever done," he said. Greenland is losing ice mass at an increasing rate, dumping more icebergs into the ocean because of warming temperatures, he said. The stark warning was underlined by the momentous break-up of one of Greenland's largest glaciers last week, which set a 100 sq mile chunk of ice drifting into the North Strait between Greenland and Canada. The ice loss from the Petermann Glacier was the largest such event in nearly 50 years. Andreas Muenchow, professor of ocean science at the University of Delaware, who has been studying the Petermann glacier for several years, said he had been expecting such a break, although he did not anticipate its size.