Mankind has been on the earth for an incredibly miniscule amount of time, cosmically or even geologically speaking. And fossil fuels have been used for a miniscule fraction of the time that Mankind has been around. I'm not saying I buy what the scientists are feeding us. Both sides serve out heaping piles o' propaganda. But if smoking is bad for you personally (and if you doubt this, you really should watch someone smoke their first cigarette), don't you think it might have a little bit of an effect on the world around you?
Nature is very adept at adapting. I think it is absurd to think we have the power to upset something we are very very new to, and a very very small part of. I really think it is the human desire to be so important and powerful that drives the idea that we have any say in how it is going to go.