Humans don't need to do anything about CO2 emissions. We'll do whatever we do, they'll do what that leads to, and other stuff will go down accordingly. Humanity may go digital, so ecosystem disruption won't matter so much, except perhaps esthetically. But whatever happens, I suspect that the ride will get bumpy for a while.

Edit: I'm not arguing against reducing CO2 emissions. I'm just saying that it probably won't happen. That shit will happen. And that, over the long term, natural selection will deal with it all.