Synopsis: Polar bears have survived much hotter and colder periods. Continued polar bear hunting is the primary danger to polar bear species.
Source here. "Polar bears have survived changes in climate that exceed those that occurred during the twentieth century or are forecast by the IPCC’s computer models. Most populations of polar bears are growing, not shrinking, and the biggest influence on polar bear populations is not temperature but hunting by humans, which historically has taken a large toll on polar bear populations."