No one knows how gravity works, but we know it exists.  I would venture to say that global warming is very likely happening - I think there is sufficient evidence for that for me to stand on that side.  But just as with gravity what the true mechanism is remains unsettled. 

I don't know how much global warming is really happening and at what rate, what the primary cause is, what degree mans' actions play in it, whether it is even bad or just a natural fluctuation in the earth's amazingly (to this point at least including ice ages and other hot periods) self-regulating thermostat as it benefits life in general. 

I'm on the fence because I find global computer models to be woefully inaccurate when back predicting and thus highly suspect for any future predictions they offer. We may not have time to wait for science to confirm what GW alarmists claim is happening, but we may do irreparable harm to our financial and societal structure by taking actions that will not effectively impact what we fear because they may be directed at the wrong cause of the problem, or useless because the phenomena may be unalterable and outside our influence even if it does exist. Or if they're right any further delay may increase the impact or prevent any effective change in time to save the current world climate we find so favorable in general.  Flip a coin at this point and have at it on message boards. 

My gut instinct says human influence is a minor part of this and any actions we take will have minor effects, but I don't know jack about the fine details anymore than anyone else.  I'd hate to win the concensus either way and then be wrong, because that way disaster lies.  To sum it up my honest belief is: either GW will self correct or we're #badword#ed.