Why are man-made global warming 'skeptics' so vehement in their beliefs?

could it be that, there is NOT clear cut evidence to support it? you can spew all the scientific mumbo jumbo you want, but it is still not clear cut. a consensus of scientist is not irrefutable proof. the worst argument from scientific stand point would be that it is a consensus, because a real scientist does not search for a consensus, but to prove the theory is fact. i would be embarred as a scientist to subscribe to the consensus theory.