Cliff, with all due respect Al Gore's movie has little to do with fact and science.
Pete, you may be right. Reasonable people can certainly disagree reasonably. There's a lot of data out there that does convincingly support the theories around climate change, man-made or otherwise, which is not derived from or related to the data AG presents. Heck, I see it in basic meteorlogical data - the weather patterns are getting stronger all the time in my area, in the US and globally. There's no doubt the polar ice caps are shrinking pretty dramatically. I see it first hand when I look at the mountains in my area (and there are many!) - 25 years ago there would be pretty good snow caps on the tops even in the middle of summer, now it's just the few tallest that still have snow pack.
Just a few degrees in climate change can cause very dramatic changes in weather patterns, distribution of rain and moisture, etc. These things affect crop production and if there are crop failures then guess what, you've got revolt and anarchy on your hands. It may sound crazy but there's a very credible theory that the French revolution was brought on by several years of crop failures caused by cooling of just a few degrees in the aftermath an excess of volcanic dust in the atmosphere associated with a large volcanic eruption. Science seems to agree that the dinosaurs became extinct because of a change in temperature which occurred over several hundred years - just a degree at a time, nothing dramatic when measured by the span of a human lifetime.
I've seen the pollution in China for example (much, much worse than in Los Angeles in the US for comparison) and after seeing that there's no way a person can't feel in the bottom of their heart that we're creating a lasting effect on the earth. It seems to me to be one of those monumental things that if you're wrong (about climate change) then you're pleasantly surprised, whereas, if you're right, you might have just acted in time to avoid cataclysmic outcomes.
As usual, there are people that twist the environmental issues to their own purpose, either economic or political or just plain self agrandizement - that's human nature. Don't let those folks discredit the basic science and facts at hand.
Again, reasonable people can disagree reasonably, because there's obviously no 100% conclusive data here (unfortunately!).