Four out of five dentists say it's the scientific consensus, stupid

I'm late to the game of the Cox/Ince editorial on science and policy, but two points:

1. It's not "science" that matters most at the intersection of science and policy but scientific consensus that does.  If there's a well-established consensus with very few expert dissenters, then you've got factual conclusions as far as policymakers are concerned.  The consensus could be wrong of course, but that's not really relevant to policymakers - they don't have a choice of waiting for a perfect consensus because that won't happen.  What's missing from the commentary I've seen is that policymakers also don't have the choice of second-guessing the consensus by becoming their own Galileos.

Let's forget climate change for a while and take my constrained policymaking field instead.  Should I direct my water district to add fluoride to our water supply?  The vast majority of dentists say it helps teeth, but some disagree.  Does adding fluoride create non-dental health risks for the general population?  The vast majority of oncologists, endocrinologists, and neurologists reflected in the scientific consensus say somewhere between "no" and "not proven," but some disagree.  It's ridiculous to think I could get sufficient expertise in those three fields as well as dentistry to let me judge between experts.

And fluoride is just one issue.  What about water supply decontamination - should we use chlorine or chloramine?  What is the maximum horizontal acceleration that a worst-case earthquake will exert on each of our eleven dams?  Is the stream gauge appropriately sited to be provide accurate data on stream flow during storm events?  How much chromium 6 is tolerable in our stored groundwater?  Can migrating steelhead trout make it up the proposed fish ladder? I'm not second-guessing these things if they have an expert consensus behind it, regardless of a few dissenters.

Incidentally, I don't distinguish between scientific consensus and other expert consensus.  Seismologists tell us the maximum acceleration during an earthquake, and engineers tell us what dams can handle.  I don't see a difference.

The intersection with policy gets complicated if the consensus has an important dissenting faction or if there's no consensus at all, but that's not what we're facing on some issues, like global climate change.

2.  Contrary to what scientists often say, the science can all-but-decide policy because some policy questions are easy.  Scientific predictions of climate change in the next century under business as usual emission scenarios run from "bad" to "potentially disastrous".  That's pretty much all we need to know from a policy perspective to conclude that we have to deal with it.  The question of how we deal with it isn't easy or exclusively a science question, but whether to deal with it was answered by science.