We'd still have protection from cosmic radiation. Antarctica is far more livable than anywhere else off earth, but I don't see us living there in a self-sustained fashion.
Space exploration and colonisation is important, but it's not an answer for the Earth's problems. It may lead to new technologies that will help on earth though - not least the requirement for sustainability.
Even if all glaciers on Earth melted and went into the ocean, sea level would "only" grow by about 65 meters.
The issue with climate change is that higher temperature means more energy and thus more extreme climate. Plus there's desertification but that is, to some extent, a different issue.
But if you're talking about terraforming, then if we could terraform another planet we could probably re-terraform earth itself.