Surely, if there is even the slightest chance that the scientists are even slightly right, then it is sensible to take steps. If by some chance they are all wrong, then we will have cut down on what we know are harmful emissions, saved rainforests and preserved some of the fossil fuel reserves for the future, as well as developing cheaper cleaner technologies. If on the other hand they are right, we will have gone some way to ensuring that our children and grandchildren have somewhere halfway decent to live.
It's all to easy to find someone to rebut anything (evolution, moon landings, the shape of the earth etc etc) but using that as an excuse to put your fingers in your ears, deride anything that you don't want to hear and to just carry on doing the wrong thing because you don't want it to be true is selfish childishness of the highest order. (I'm looking at you Agent Orange!!!)