Thursday, January 03, 2013

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.


David B. Benson said...

Well stated.

Martin said...

Is 2. true ?

If global warming is a net bad or not is a question of how much we need to cause it in order to further or maintain our well-being (for simplicity, let's assume that there is no problem with this notion), or at the very least to not deteriorate it more than impacts of warming do. Turns out, in each and every calculation since the very first one, that this net grows negative rather rapidly if we rely on emission intensive technology and can well be sustained a positive using others, though the transition seems rather tricky. But it is a question that cannot, as a matter of principle, be answered by science alone, neither conceptually nor quantitatively.

Btw, yes, I hate what some idiots make of the 'it hurts the economy' argument when it comes to mitigation policy (especially as they usually mean the economy to be a maximiser of private business revenue instead of social welfare). But as I said, the economics here is clear in sign, just not in magnitude, given the many value judments involved. But that there are idiots doesn't make the question go away. (Even if one sees economics unfit to tackle the question, it does not make it go away, but just tells us that we do not have the means to answer it...)

Mark said...

Say Hello to Martin, my sockpuppet.

Sorry, was by mistake...

Brian said...

Hello Sockpuppet Martin (i.e. Mark): agreed that science can't tell us how much mitigation to do and when to do it, but it can take you almost all the way to the conclusion that you have to do something.

I see a lot of this as an iterative process between scientists, economists, and engineers, all providing some real answers or paths to answers. There are value judgments as well such as handling uncertainty, deciding who pays and determining which non-monetized interests are worth protecting, but there's still a lot that can be farmed out for technical solutions.

Mark said...


agreed. I was quibbling with the statement "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." Apart from the obvious catastrophy part, science can tell us no such thing without genuine economic contribution - we have no idea if +4 °C is net positive or not without, for example, asking how much growth is possible without those emissions leading to +4 °C etc. etc. As we know for quite a while now, it is indeed negative, as negative impacts of warming begin to outweigh everything else. Without economic analysis, we could just throw up our hands and guess. Catastrophic risk might break the neck of conventional cost benefit analysis, but that does not magically settle the matter outside of economic reality (and anybody being alive these last years knows that it is indeed a reality, if we can assess it or not), it just renders it much harder to do.

Hank Roberts said...

> we have no idea if +4 °C is
> net positive or not

You have no idea about the rate of change, do you?

"You seen one Earth, you've seen them all." -- Harrison Schmitt

Mark said...

Hank Roberts,

I have no idea what you are talking about. Perhaps I have no idea about the rate of change, I don't know. Rate of change is such a mysterious concept: just state it, and there you go! I admit defeat.

You cite me as saying "we have no idea if +4 °C is net positive or not". Not so, we do know that it is net negative, and we know it because that is what each and every economic modelling of +4 °C scenarios is telling us. That was the point.

"But, now they are all Borg. " -- The Borg Queen

Brian said...

I think you can eyeball the impacts and conclude it's bad with a 2 to 2.5C change. Economic analysis helps but isn't necessary.

My backup argument is that technical analysis by economists is in the same general realm as that by scientists. Economics is much harder, but if you've got an expert consensus there, then just plug in the results of the consensus. If you say "I insist economics is also required" my response would be, "regardless, that doesn't really change my argument".

Hank's argument is similar to a comment Dano once made, that our economic system depends on our ecosystem as it currently exists. Alaska could conceivably benefit economically from a very slow warming, but it is currently being harmed by the fast warming it experiences. No sophisticated economic analysis needed for that.

Mark said...


I don't know if your comment has anything to do with mine. If so, I completely failed to convey what I meant to say.

As you put it, all you take into account is damage caused by warming. This, of course, scientists can tell us. Perhaps economists can contribute to that, e.g. by conveying damage costs in a more comprehensive way, but that's pretty much it (even though this is important). I completely agree.

But that was not my point. As it is, our economic activity (the very prerequisite to social welfare) necessitates GHG emissions; unfortunately we cannot yet rely on exclusively emission-free, sustainable energy ressouces or do the switch overnight. How fast and how much we can reduce emissions while maintaining a specific (and sustained) level of social welfare is an economics problem, and nothing else but an economics problem.

This, of course, we have to gauge against the damages done by global warming. But these damages alone tell you nothing at all about if or how much we should act, apart from the no-brainer that we should avoid total catastrophy (and even here an economic analysis is absolutely necessary if our response is to be anything else but immediately destroying all social welfare by shutting down emissions overnight, or something the like.)

I am surprised that this is apparently under dispute. The whole point of literature like the Stern Review is to do this kind of analysis. Really, is there a widespread impression that all climate change economics does is estimating climate change impacts?

Of course, as regards economic welfare there are a lot of ethical judgments to make (e.g. whom to include in our considerations, be it in time or space, and how much so). Also, one can quibble about the exact meaning of social welfare etc. But all that doesn't change the principal argument.

Mark said...

Or to put it shorter: anybody convinced that we need no economic analysis to base our decisions on please tell me how to respond to global warming without referring to an economic argument implicitly or explicitly.

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