Climate change is starving polar bears into extinction, according to research published Monday, which predicts the apex carnivores could all but disappear within the span of a human lifetime. In some regions they are already caught in a vicious downward spiral, with shrinking sea ice cutting short the time bears have for hunting seals, scientists reported in Nature Climate Change. Their dwindling bodyweight undermines their chances of surviving Arctic winters without food, they added. mh/jj