I responded in this post, linking to a response from the petition organizers. Of course, if the premise is that anyone with a countering position is automatically a liar in the pay of evil forces, that's probably not much use.

I can't speak for everyone in that petition from my own independent research. I do have a life. But if a tenth of them are valid signatures, that still leaves quite a number.

Another list of people who have doubts about the current baseline here. They can't all be lunatics.

I am not a scientist schooled in the details of climate science, but some issues are open to rational questioning by a thinking layman. I've put them up here in the past, and not gotten much in the way of rational responses.

It's basically pointless to argue about the science any more. I suspect that in the future, few scientists are going to bother investigating anything counter to the current political wisdom. What would they have to gain, compared to what they would have to lose? And it's not like climate change is the only scientific arena where there are "untouchable" questions.

It is also pointless to state that the pro-AGW scientists have their own financial and political linkage problems. Apparently only private energy companies can corrupt science in this way.

It's a religious argument now, and people like those at realclimate.org are basically the Jesuits.