The first type of ‘lay’ skepticism is the doubt about the facts. The issue is of ‘what’. Generally, more people are content to agree that climate does in fact change, and is changing now, than are inclined to have other doubts. Perhaps this is because we are well-trained to understand that science is good at questions of ‘what’, in other words, the recording and observation of fact and its reporting, of measurement and the observation of trends. Really, there shouldn’t be any debate about this at all, since either the climate is warming or it is not, and either it is being correctly measured or it is not, but even here, the lay reader can be drawn into doubt by skeptics or scientists who cast doubt on the reliability of observing systems or of methodologies.
We don’t understand the problems, but we do understand that the existence of a ‘problem’ in itself casts doubt on the reliability of the claimed facts. Thus, if we are already disposed to skepticism, our doubts are reinforced by the very existence of disagreement; we are able to say ‘See, it isn’t all that certain after all…I am right to have my doubts, since some scientists also have them.’ This skepticism can be challenged by reason and evidence, though people still tend to see only what they want to.
But the second type of issue is far more difficult to deal with. These are the issues not of what is happening to the climate, but of why. We are inclined to understand debates on causality as being more uncertain than issues of fact, since they are often not easily resolvable by purely scientific method, and they are, in our minds, ultimately ‘matters of opinion’. Of those who are skeptical about AGW, more have doubt about the causality than the observation. Here is where the do-nothings have their richest ground; there are many ways to reinforce peoples’ predisposition to doubt when the issue appears, on the surface, to be about matters of opinion.
As well as his well-argued position, I like Brown's title: The Skeptic problem
It's not something that will go away soon enough.