Reuters: 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 …