Nasa has released satellite images that show unusually rapid melting of a huge sheet of ice across Greenland. Even Greenland's coldest place showed melting, and according to records this was last seen in 1889 and occurs once every 150 years.
According to the agency, three satellites saw what it calls unprecedented melting over four days beginning 8 July. Though the bulk of the thick ice remains, what scientists found unusual was that the melting had occurred over a widespread area.
Scientists found that the melting had been very rapid from 40 per cent of the ice sheet on 8 July to about 97 per cent on 12 July. Till now, the most extensive melt recorded by satellites over the past 30 years had been 55 per cent.
However, it was not clear whether melting was from global warming or natural, say scientists.
One expert even initially suspected that the satellites had made a mistake.
Son Nghiem, of NASA's Jet Propulsion Laboratory in Pasadena, California, was analysing radar data from the Indian Space Research Organisation's (ISRO) Oceansat-2 satellite last week when it came to his notice that Greenland appeared to undergone unusually extensive surface melting.