Cue the inevitable claim/counterclaim "discussion"...
The problem with global warming is that the issue has become totally politicised in the worst possible way so that clarity has become near impossible.
Some will have you believe it's an entirely natural phenomenon, others will have you believe it's entirely caused by human activities.
The truth of the matter is that nobody is sure what the current trend really indicates. That said, it's my opinion that given there is evidence to suggest we are aggrivating the problem we should do what we can to minimize that effect and see how it pans out. It's the logical course to take. Unfortunately, governments rarely, if ever, consider anything beyond their term in power. Given we could be looking at massive problems in say 50 years time and not tomorrow, no existing government really cares.