Unusually warm western Pacific waters linked to global warming may be the paradoxical cause of a bone-chilling winter in parts of the United States earlier this year, a new scientific study says.

The theory contrasts with some other experts' views, including that the freeze was simply a freak natural event or that it was linked to a thawing of the Arctic in recent years that sent a blast of cold air south.

"People's reaction when they sit under 10 feet (3 meters) of snow is to say, 'This cannot be man-made climate change,' " said professor Tim Palmer of Oxford University, who published his research in the journal Science. "But there is a plausible link."