Just a clarification on your original question: there is only a general scientific consensus that gloabl warming is occurring. That humans are causing global warming is where the controversy begins. The theory that humans are causing global warming is drawn from a correlation between temperature and industrialization. It is this same sort of correlation that started the 'babies come from storks' mythology (storks stand on warm rooftops during winter, people stay inside more in the winter and occupy their time making babies).
It is entirely possible that humans are accelerating global warming - but many scientists point out that we're at the tail-end of an ice age. Since the earth goes through hot and cold stages, how would we know if this warming was not part of that trend?
Since scientists must follow strict definitions of causation, there can be no scientific consensus on human-caused global warming. It's an issue of faith.
That doesn't mean it's not true - just that it's not technically supported by science.
The more interesting question for me is on climate change in general. Humans do not like change; they try to see everything as a 'balance' or 'ecosystem' which is really just a static snapshot in time instead of the dynamic process. This becomes obvious when you hear the term 'upset the balance,' as if a static balance were its natural state. If it were proven without a doubt that global warming was not influenced by humanity at all, would we still try to fight it?
Of course we would. But how would we do that? Hmmm. To believe that change is preventable, we have to believe that we can control the change, which is much easier when you believe we are causing the change the change in the first place. It's a circular argument, but most people are more comfortable with a circular argument than the thought that we are at the whim of forces beyond our control.
