WASHINGTON - There's more to the recent dramatic and alarming thawing of the Arctic region than can be explained by man-made global warming alone, a new study found. Nature is pushing the Arctic to the edge, too. There's a natural cause that may account for much of the Arctic warming, which has melted sea ice, ice sheets and glaciers, according to a study published Thursday in the journal Nature. New research points a finger at a natural and cyclical increase in the amount of energy in the atmosphere that moves from south to north around the Arctic Circle. But that...