InsideClimate: Polar bears have been one of the species hit hardest by climate change over the last decade, experiencing population declines up to 40 percent in some areas. Even so, scientists have long held out hope the mammals might adapt in some way to their melting Arctic habitat and reboundor at least stabilize in numbersas the world continues to warm. But new research published Thursday in the peer-reviewed journal Science deals a blow to that optimism. Eight U.S.-based scientists tested a leading hypothesis...