Well, its all over the place - Global warming this , ozone layer that ... I Know we have made a large impact on the Earth as a whole but we really are not that significant. The Earth as we know it has been around millions of years and as far as we can tell it has changed dramatically on many occasions. Take the last know Ice Age, Humans were but a speck on the land then - No cars , No factories or other pollution, but the Earths climate changed. The Dinosaurs died out, maybe an asteroid or meteorite maybe just bad luck, but Humans wern't there!
Lets face it we can do a lot to ease the pollution we may even kill off what is known life today, but Life will continue it always has and i'm sure it always will. But we are not the cause for changes in the environment, Nature is and we stand very little chance of beating her...

Global Climate: Speech