I doubt we've come to a point where we can change the planet enough to drive ourselves off of it by changing the climate. While we do emit pollution and take out forestry, I think most of the changes we observe in the climate should be blamed on natural movement and changes of the earth.
Humanity will either kill itself off as a result of nuclear warfare or disease, and I think the planet will exist as long as either the sun does, or as long as we're not obliterated by a massive comet.
