I won't say global warming exists or doesn't, but I will say that based on the evidence provided by both sides, as well as the people and techniques used to accrue that evidence, it seems most likely that nobody has any real clue as to what is going on.
Glaciers in the Norther Hemisphere are melting at what some call alarming rates, while ones in the South are growing at rates never before seen. I think we can all rule out the idea of the polar ice caps melting since it is so cold that even a 30degree average increase wouldn't even come close to melting them.
I also think that a lot of the talk supporting global warming is a scare tactic used by certain ex-politicians to promote their agenda that supports the people who give them money ("green" energy) but I think it is important that we not lose sight of the impact we can and do have on the environment; pollution, deforestation, strip mining, and have to ask ourselves, what cost are we willing to pay for "progress."
But, I think in no more than 30 years we'll look back at the global warming debate and look at how foolish we were regardless of what the verdict is.
Bottom line, environmental science of this nature is similar to avalanche science, nobody really understands either completely, and people who claim to should be viewed with great skepticism.