Well there's no doubt that global warming is happening. How much we are contributing to it is up for debate. What we know for sure is that when it happens, it will cause many of the world's coastal cities to be submerged underwater and widespread economic ruin.

The real question to ask is not whether we're responsible for it, but what we're going to do about it.

Sure we are polluting the hell out of our ecosystems. But not with co2. Because the link between co2 and the greenhouse effect is a sham. The fossil record clearly shows that during the past ice ages, the polar ice cap (northern) melted completely and suddenly, at least 4 times, and the polar bears clearly survived. All while the co2 level in the atmosphere was lower than what it is today. What caused that? Not us. We were still climbing trees in Africa to get away from leopards at that time.

I think that we can do a lot to preserve natural resources and habitat. But it has nothing to do with co2. Regulating it is hitting a mosquito with a hammer, and it's not the root cause anyway. Regulating the real greenhouse gases will do a lot more good, and cost one-hundredth as much in terms of money and human capital.

I don't want to waste my time to refute crazy denialism talk. Or like Al Gore once said:

"I want to be polite to you," Mr. Gore responded. But, no. "The scientific community has gone through this chapter and verse. We have long since passed the time when we should pretend this is a 'on the one hand, on the other hand' issue," he said. "It's not a matter of theory or conjecture, for goodness sake," he added.

The only reason why I did not delete your post was that it was somewhat civil compared to the rest of the deniers posts. But I am always forgetting that you should never feed the trolls.

As to your question, instrumental records suggest a warming of 0.6°C over the past 100 years. Even if you ignore all the recent work that’s been done to suggest there are major siting problems (http://www.surfacestations.org/ across the USHCN), as well as James Hansen’s embarassing blunder this past August (http://www.climateaudit.org/?p=1885#more-1885), that is all that comfortably can be said about recent climate change. Remember, these are errors found in the most high-tech monitoring system in the world, and they were found AFTER the release of AR4 and the trumpeting by the IPCC brass of “The Science Is Settled”, “The Warming is Unequivocal”, “We Must Act Now” etc. etc. The entirety of work done by the second and third working groups are rendered totally useless until these things are ironed out.

Further, it can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries. This statement is justified by the consistency of the evidence from a wide variety of geographically diverse proxies.

Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified.

Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods."
-From the NAS report.

So I guess what I need to as is "What it would take to convince you that any science, be it for or against AGW, is suspect. And, on the flip-side, what would it take to convince you that the science is credible? And how is it credible?"