OSLO—Climate change has caused the greatest thaw of Greenland’s ice in half a century, perhaps heralding a wider meltdown that would quicken a rise in world sea levels, scientists said on Tuesday.

"We attribute significantly increased Greenland summer warmth and ice melt since 1990 to global warming," a group of researchers wrote in the Journal of Climate, adding to recent evidence of faster Antarctic and Arctic thaws.

"The Greenland ice sheet is likely to be highly susceptible to ongoing global warming," they said. Greenland contains enough ice to raise world sea levels by 7 meters (23 ft), a process that would take centuries if it were to start.

Melt water from Greenland – excluding ice losses from glaciers slipping into the sea – totaled 453 cubic kms in 1998, the most ahead of 2003, 2006, 1995 and 2002 in detailed records stretching back to the 1950s.

Preliminary data showed that 2007 would rank second or third highest and confirm the last decade as the biggest melt, said Edward Hanna of England’s University of Sheffield who led the study with colleagues in Belgium, the United States and Denmark.

So far, the water runoff has been largely offset by rising snowfalls in Greenland that may also be a side-effect of climate change. Even freezing air can hold more moisture, and so deliver more snow, if it gets slightly less chilly.

But continued warming could threaten an irreversible meltdown. The report noted that typical climate models pointed to a warming for Greenland of 4-5 degrees Celsius by 2100.

"The ice probably wouldn’t grow back under current conditions," Hanna said.

"If you have an extra 3-5 degrees Celsius warming ... then you can reach a point of no return ... bringing the eventual demise of the ice sheet. That could take probably 1,000 or 2,000 years," he said.

On Monday, a climate researcher said that Antarctica lost billions of tons of ice over the last decade, contributing more to rising sea levels around the world.