Arnold wonders:

There are conservatives and libertarians who believe in CO2-caused global warming. As far as I know, there are no liberals who are skeptics. I wonder why this is the case.

It's an interesting question. Politics is the obvious answer - statists see this as a stalking horse for their socio-economic agenda and hope to ride it to power and dominance. Other's fear that this is so.

One of Arnold's possibilities is more interesting.

[I]n economics the belief in the macro-econometric models of the 1960's tends (or tended) to be higher among liberals than among conservatives. I think that liberals have a genetic defect that allows them to believe that they can model complex systems effectively, while conservatives and especially libertarians see limits to knowledge.

It's not likely a genetic problem and not clearly a defect, but the idea has merit nonetheless. I've posted about the problems in paleo-environmentalism that arose from the unquestioning belief in simplistic models of ecosystems and societies.

Such models have never seemed compelling to me. They all have obvious defects: simplifications for computational convenience, and unfounded base assumptions that bias the results in ways that appeal to the modelers but that can't be objectively supported. Even when I like the results and wish they were true I can't bring myself to belief.

How does it happen? How do people do that mental flip that allows them to ignore contrary evidence and sketchy reasoning? I've always figured that it's something like religious belief, that faith rather than reason is the operative power. Somehow they just know that something is true though they haven't yet figured out how to prove it. Once they have fallen into belief then no contrary evidence short of total failure moves them, and even then they don't always recant.

It's not that our clumsy attempts to describe and model systems have no uses, It's that they are flawed and unreliable, and we know it. We can't lean on them too much since they have an annoying habit of collapsing when we are off balance and most need support. In some ways they are just a hobby, or perhaps like a journal where we doodle, jot ideas and maintain a growing, patchwork system description, a record of our previous insights. They are obviously cartoons and will always be so unless we are miraculously stricken with omniscience.

That seldom happens.