Alarmists have adopted the seemingly farcical but oddly effective technique of finding the most absurd skeptic argument they can, then beating the carp out of this straw man, and then claiming that this proves that all skeptics are anti-science.
Don't believe me? Kevin Drum did it yesterday, bravely taking on a claim -- that atmospheric CO2 concentrations have not increased in the last century -- that I have never seen a skeptic make and I am pretty active in the community. Having beaten up on this odd, outlier position, he then claims this tars everyone who does not agree with him
Nonetheless, there you have it. In the tea party precincts of the conservative movement, even the simplest version of reality doesn't matter. If cheese denial is how you demonstrate you're part of the tribe, then anyone who denies cheese is a hero. The fact that you happen to be happily munching away on a slice of pizza at the time doesn't faze you at all.
Awesome. So by this logic, everything Kevin Drum says about the environment is wrong because some moron environmental activists signed a petition against dihydrogen monoxide in a Penn and Teller Bullshit! episode
So, as a public service, I wanted to link to Roy Spencer's list of 10 skeptic arguments that don't hold water. There are quality scientific arguments against catastrophic man-made warming theory. You don't need to rely on ones that are wrong.
I agree with all of these. I will say that I used to believe a version of #5, but I have been convinced as to why it is wrong. However, it is still true that CO2 has a diminishing return effect on warming such that each additional molecule has less effect on warming than the last. That is why climate sensitivity is most often shown as degrees of warming per doubling of concentration of CO2, meaning 400-800 ppm has the same effect as 800-1600ppm.
Postscript: Drum choose to lampoon a position that is such an outlier it did not even make Spencer's list. Spencer assumes even the craziest skeptics accept that CO2 is increasing, such that the bad science he is refuting in #7 relates to the causes of that increase.