We are actually in an Ice Age right now, although a mild one. The normal state of the earth has NO permanent ice on it (ie the polars). However, the climate of the earth is EXTREMELY unstable, and the slightest fluctuation can send the climate spiraling up or down.

Regardless, no matter what we as humans do, it will have a huge effect of the climate. We really don't know exactly WHAT it will do, but it will do something.

It's really just a gamble.