I've recently been involved in an exchange with Mike Huben in the comments section of an earlier post to this blog, having to do with global warming, hurricanes, and Chris Landsea's pulling out of the IPCC—the group that does the "official" reports on world climate—a few years ago. Interested people may want to look at our exchange and at the web pages cited.There is a more general issue that such disputes raise: How, in controversies where most of us do not know enough to form independent opinions, one should decide who to believe. One way is to look at the incentives various people have to express the views they do.Let me start with the case of nanotech—specifically, whether it presents dangers that call for government regulation. I've been involved, at least peripherally, for a long time and know some of the people at the Foresight Institute, the group that pushed the idea of nanotech for many years before it became suddenly fashionable. One thing I know about them is that that their general political biases are libertarian. Hence when I observe them expressing serious concerns about the dangers of unregulated nanotech, I am inclined to take it seriously. They may be wrong, but they aren't believing it because they want to believe it.Mike Huben, if I understand him correctly, wants to view criticism of evidence for global warming as the work of sinister interest groups, in particular energy companies. I suspect that to some degree he is right; clearly that are industries that will be injured if countries adopt the sorts of policies recommended by those concerned with the threat of global warming, and I expect such industries do their best to push arguments that it is in their interest to push.On the other hand, a scientist such as Landsea, who apparently wrote a good deal of the relevant part of the previous IPCC report, has no such incentive—unless Mike can point to evidence that he is being secretly funded by the oil companies, which nobody seems to be claiming. It's hard to see any likely reason for his actions other than the belief that the scientific work of himself and others was being misrepresented in order to push a political agenda. And the followup articles—the ones Mike found and pointed out to the rest of us— suggest that in fact Landsea's view of the subject was correct and that his protest was one factor in pushing the IPCC, in its most recent report, to give a mostly accurate account of the current consensus. Their summary account reported that there was no clear evidence of a trend to more hurricanes. One of the authors of the relevant part of the report, decrying misrepresentations in the media, wrote that:"We concluded that the question of whether there was a greenhouse-cyclone link was pretty much a toss of a coin at the present state of the science, with just a slight leaning towards the likelihood of such a link."My current conclusion, looking over what I can see of the opinions of people who don't have an obvious axe to grind in either direction, is that global warming is probably real, is probably but not certainly anthropogenic, is probably not going to have large effects on size and frequency of hurricanes and is probably not going to have large effects on sea level. It is a real problem but not, on current evidence, an impending catastrophe.Mike, and many other people, see it as a much bigger problem than I do. My reason for distrusting their conclusions is the same as Mike's reason for distrusting the conclusions of global warming sceptics: On the whole and with, I am sure, some exceptions, they appear to me to be believing what they want to believe.I see it that way because:1. Governments, and people in government, seek power for obvious reasons. Over the past fifty years the intellectual justification for the large expansion in government power from about 1930-1970 has largely collapsed. The belief that capitalism is inherently unstable and inefficient and must be fixed with large elements of governmental intervention and central planning is no longer taken very seriously by either the general public or economists.Environmentalism in general and global warming in particular provide new arguments for expanded government power, new taxes, and the like. That does not mean, of course, that those arguments are wrong, but it does mean that there are a lot of people who have an incentive to support them whether wrong or right. That seems to me consistent with what I observe—what is probably a real problem being extensively exaggerated for political reasons, with a predicted sea level rise of up to 80 cm over 93 years being reported in terms of massive flooding around the world, converting the World Trade Center Site into an aquarium in the piece I commented on in my earlier post.2. Global warming provides arguments for things that a lot of people, mostly left of center, want to do anyway—shift lifestyles away from automobiles towards mass transit, reduce consumption of depletable resources, and the like. Environmentalism is in part a real argument, in part a religion, in part an aesthetic; the second and third parts make people too willing to accept the first.Which gets me to Mike's various queries about why I choose to align myself with the forces of evil and ignorance by expressing skepticism about the horrors likely to arise from global warming. Simply put, I am skeptical of conclusions that appear to go well beyond the scientific evidence, pushed by people who have reasons to want other people to believe them.