Arctic waters will be completely ice free within four years, according to leading Arctic ice expert Professor Peter Wadhams of Cambridge University.

This "final collapse" of Arctic sea ice in summer months could occur by 2015, solidifying a "global disaster," which has arrived faster than previous predictions suggested.

Wadham has worked for years examining ice thickness data. "The main cause is simply global warming: as the climate has warmed there has been less ice growth during the winter and more ice melt during the summer," Wadham told the Guardian.

"Climate change is no longer something we can aim to do something about in a few decades' time," Wadham said, urging that we need to immediately reduce CO2 emissions.

"This collapse, I predicted would occur in 2015-16 at which time the summer Arctic (August to September) would become ice-free. The final collapse towards that state is now happening and will probably be complete by those dates".