Why do deniers keep asking this question? The answer is simple -- global warming is not the ONLY threat that polar bears face. If we only think in terms of absolutes, black and whites, then we will never have an understanding of the real world.
Hunting and poaching is also a threat to polar bears. By the 1970's hunting and poaching had almost wiped out the polar bears. The populations fell to as low as 10,000 in the entire world. Because of global cooperation (not an easy feat in the midst of the cold war) restrictions on hunting were placed, and polar bear populations have started to make a come back.
So, while some polar bear populations are increasing because of restrictions on hunting,[1] almost everyone agrees that the overwhelming threat to polar bear population today, is the loss of sea ice.[2][3] The Arctic is expected to be ice free during summer months by mid century. By some accounts this will happen as early as 2013.
Polar bears are considered marine animals because of their integral link to the sea and to sea ice. They live much of their lives on the sea ice; it serves as a moving platform from which they hunt seals – the mainstay of their diet.[4][5]
Because of loss of arctic sea ice, the US Government, Department of the Interior, predicts that Alaska's entire population of polar bears, along with 2/3 of the world's polar bears will be gone by the middle of the century.[6]
Currently, of the 19 polar bear populations, the two which where most affected by over hunting are still recovering. The two most studied populations are known to be declining. And there really isn’t enough information on the 15 other population to determine if the numbers are faring with climate change.