if it eases any pains, Polar bears have existed as a 'species' for less then a million years. If the temperature went up so drastically that they lost too much ice, they'd just move back down south and re-adapt into Brown bears. But that future probably won't happen since we have more polars now then we've ever had (their population was always small)
Love the pic lol, I was told that some other planet (forgot which one) was going to turn into Earth and then Earth will turn into that planet in its first form and then everybody will move across the galaxy lol. But my unreliable source said that it would be billion of years in the future or whatever. Crazy eh?