I don't totally agree with you, when you say a long time ago, how long ago do you mean? Homo Sapiens have been on this planet less than 2Ma and civilization can be traced back to less than 8k-10k years. On an evolutionary scale that is iniscule.
We constantly change the climate around us 24/7 what with air conditioners and space heaters all over the world. This seems to be doing the same at a very large scale.
Every species, no matter how tiny has a profound effect on the atmosphere around it, this will in turn change things for better/worse, the success of a species depends on how fast it's able to adapt to the change, perhaps even make it work to it's advantage. For a species to successfully adapt, the change has to be very gradual.
Survival is the most basic instinct in any creature, we're just trying to survive by doing what we do best: change the conditions around us instead of evolving to adapt to them, perhaps that's our way of evolving.
I agree though we shouldn't try to change it on such a large scale, nature comes back to bite us in the ass every time we fiddle with it but it doesn't mean was give in to our fate and die out without trying. :)