I was mostly talking to greeny, not you...
That said, I have talked to some of the people here in Berkeley as well as at Stanford and the University of Washington (state, not St. Louis) and seen 2 or 3 talks from experts in the field, people spending their lives studying global warming, and even these guys aren't willing to go so far as to say that they're 100% certain that there is meaningful human influence on the climate, only that it's very likely. Most would say something along the lines that they're quite sure, but can't defend a definitive statement about it. Certainly the degree of human influence is nearly impossible to determine but could be fairly small, or rather large. But the people, mostly greeny but a few posts from other people, talking about one year, or one season, or one day and using it as evidence of global warming basically sound like idiots. We've only been keeping weather data for ~150 years, at some point it's going to be the hottest day or the hottest summer in 150 years, and that's not nearly a long enough time frame for it to mean anything. The mid 1900s through late 1910s were warmer than anything until the '90s, and certainly there was a lot more industry and burning of fossil fuels in the '60s, '70s, and '80s than those warmer times. Several times more, if not an order of magnitude or better. These are the people who went to see An Inconvenient Truth and came out thinking the end was near and Al Gore is a genius. Everyone I know with a legitimate science background and without a massive pre-existing bias came out of that movie thinking Al Gore was a moron. It was horribly exaggerated and misrepresented findings left and right. The reality is that the one major paper in Science expounding the magnitude of global climate change shows little data. Typically papers in Science or Nature, since they must be short, cite another paper by the same author on the same work which shows all the data, the work, and really explains how the results were determined. The climate change paper has no such analogue. Ironically, the desire of the big journal to have the cutting edge and shock value type articles allowed it in, but all the more subject-specific journals found the actual research too shoddy to publish. This is the #1 piece of "scientific evidence" typically cited by the more-educated proponents of climate change. The reality is that the scientific community isn't really ready to make any major statements on the subject. All the same, it would be wise to take steps, because, as you said earlier, coming back from a real problem is very difficult. Cutting back on CO2 emissions may be expensive in the short term, but the reality is it's going to be essential as fossil fuels run out anyway. Why not accelerate the process, preserve some oil, and not take the risk?
Wow, that was one hell of a paragraph...