Just general comments on the subject fom discussions I've had before -
Unfortunately, this is one of the more conspicuous examples (not meant to be sarcastic - but polar bears ARE big, fluffy, and cute) of how environmental change affects habitat. The habitat of polar bears, which depends on cycles of freezing and melting arctic ice at regular intervals, is in jeopardy because of global warming.
We're still coming out of an ice age, a phenomenon that was well under way long before any human activity had the opportunity to possibly accelerate the process.
My main contention is that our planet and its natural phenomena are immeasurably powerful. Creatures became extinct or evolved under equally violent circumstances long before we were ever a species.
Taking a this-is-the-fault-of-humankind position on this specific matter is fundamentalist and presumptuous. Sometimes the world changes on its own accord. It would do us well to consider this, so that we can look upon the potential of our efforts to minimize OUR impacts with greater clarity.