Science and Motivated Skepticism

A fun new headline which might make a splash in the blogosphere in the near future:

World misled over Himalayan glacier meltdown

A WARNING that climate change will melt most of the Himalayan glaciers by 2035 is likely to be retracted after a series of scientific blunders by the United Nations body that issued it.

Two years ago the Intergovernmental Panel on Climate Change (IPCC) issued a benchmark report that was claimed to incorporate the latest and most detailed research into the impact of global warming. A central claim was the world's glaciers were melting so fast that those in the Himalayas could vanish by 2035.

In the past few days the scientists behind the warning have admitted that it was based on a news story in the New Scientist, a popular science journal, published eight years before the IPCC's 2007 report.

It has also emerged that the New Scientist report was itself based on a short telephone interview with Syed Hasnain, a little-known Indian scientist then based at Jawaharlal Nehru University in Delhi.

Hasnain has since admitted that the claim was "speculation" and was not supported by any formal research. If confirmed it would be one of the most serious failures yet seen in climate research. The IPCC was set up precisely to ensure that world leaders had the best possible scientific advice on climate change.


Pointing out failures in environmental science tends to invite all sorts of accusations upon the speaker. Among baser epithets, you'll face charges of denialism, or at least a kind of crypto-denialism and various sorts of motivated skepticism. The ubiquity of the term "denialism", being not-so-subtly meant to evoke the rawer emotions associated with Holocaust denialism, would do George Lakoff proud. Skeptics have fought back by drawing parallels between environmentalism and a sort of secular fundamentalism; the environmentalists, tending to be fond of the term "market fundamentalism" itself, cannot dismiss this metaphor at the outset and instead get bogged down into debates over whether environmentalism is really like religion - at which point they've already lost.

I'm not going to press this metaphor seriously, but if environmentalism is to be likened to a religion, then the vaguely-defined "scientific community" would undoubtedly be its clergy. Its higher-ranking members, through their communes with tree rings and ice sheets, speak ex cathedra from Nature Herself - or something like that. Of course, this authority only extends to the community of environmental scientists. As an economist, this deference to Science doesn't cover my discipline. I realize that the credibility of economists is at something of a nadir at the moment, but let's not pretend that it was ever that high to begin with among Science-touting left-of-center individuals, even despite the existence of a strong professional consensus on many issues that are of great contention among the general population. As Bryan Caplan (whose book, The Myth of the Rational Voter, is required reading on motivated political cognition) might observe, economics is relatively unique in its being respected as a science without its actual practitioners being given the usual intellectual deference which comes with the mantle of expertise.

I'll admit that this is somewhat embittering - that not believing in AGW can make you a pariah who is (gasp!) "anti-science", but believing that rent control is an awesome idea that only hurts rich people - often the "Other", as it were - is perfectly respectable, or at least understandable if you've spent your life learning about more important things than what happens when prices can't rise to clear a market. When you tell someone that the professional consensus is against their personal view, you're usually told either that economics is a "right-wing (or left-wing) discipline", or that economists rely on a poor model of human behavior which renders their entire discipline useless at best and dangerous at worst - didn't you know that the financial crisis discredited free markets?

But a little skepticism really isn't a bad thing. It's somewhat reassuring that the people who trumpet Science in the context of the environmental debate are such keen skeptics of the economic discipline - it shows, at least, that they do have an understanding of the general process through which the scientific investigations can be derailed. Stories like the one linked above and Climategate reveal many of the unsavory processes that are actually at work in generating consensus - scientists misrepresenting/losing/hiding data which might have been selectively chosen and shoddy, trying to silence dissent for political or financial reasons, "common wisdom" being based on narratives hopelessly distorted in a telephone game of motivated communication. This is the norm of how politicized science proceeds when the black box is cracked open, and it's understandable that environmentalists act far dumber than they actually are in trumping up the fidelity of consensus.

Trying to determine what the ex ante "optimal level of deference" to be afforded to a given expert or set of experts is an incredibly difficult problem. But like most things in life, it's probably somewhere between "none" and "infinity" - and not embracing the latter extreme does not make you "anti-science." These kinds of labels might make for effective politicking, but those who employ them would make themselves rather ironic champions of reason and science.

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I've run across this exact type recently

A self-proclaimed "person of science", a "progressive", who thinks the case for AGW is open-shut, refusing to listen to any skepticism about it. When I point out that proving cause-and-effect in this case is very difficult due to the lack of a controlled study being possible, and thus, the type of science available (mechanistic modeling) is much more unreliable, he brushes it off.

Yet, he's quick to point out that economics is a pseudo-science since there's no proof that it predicts anything, and that its model of people is overly simple. This of course leads him to make some of the worst arguments possible about the political economy.

On deference to experts

Here's my take:

Because controlled studies can't be done to evaluate AGW, it's all mechanistic science: A causes B which correlates with C which seems to give rise to D. Thus, it's likely that A causes D.

Controlled studies, I can evaluate relatively well, even outside my field. Mechanistic science, I can't. You really have to dig in, read up, and get to know the data before making an informed opinion.

I have no desire/time/motivation to do such a thing. Thus, I yield to the experts, but only marginally. Before Climategate, my p for AGW was 0.6 as more scientists than not seemed to believe it was happening. Why 0.6, and not 0.7 or 0.9 or something else? It didn't seem like scientists were close to united in their views.

After Climategate, even I was shocked at how politicized the whole process is, and my p is back down to 0.5.

Sadly, most people just

Sadly, most people just don't think about these issues in Bayesian terms, and they certainly don't understand how anyone could approach evidence with a different prior probability without being stupid or disingenuous. These kinds of events tend to create a net increase in disagreement rather than a net decrease.

A related idea that I had in mind - maybe I'll turn it into a post later - is about how the relevant margin of argument in the climate change debate is very rarely about "is AGW occurring?" This is arguably to the dismay of environmentalists, because once this point is conceded, then you have to deal with issues of what the magnitude of the risk is, what the policy prescription should be, etc. There's much less consensus on these issues from the Scientific Community, so you tend to see evidence-based rhetoric jettisoned in favor of a "something must be done, this is something, therefore this must be done" approach.

I agree re Bayesian

I agree re Bayesian analysis.

But Bayesian analysis makes one thing clear: when it comes to risks, uncertainty is NOT your friend.

We're stuck in an absurd situation where the public debate seems stuck on whether or not to believe so-called "skeptics" who are arguing that AGW doesn't exist or isn't much of a problem. But far more climate scientists think the IPCC projections (of a 90% chance of between 2 and 5.5 degrees rise by 2100) are overly optimistic than overly pessimistic.

Yet there's little serious public debate about the 5% chance that we're looking at over 5.5 degrees of average global warming by 2100. A 6 C average global rise is quite possible (if we're talking 5% then it's around the same chance as being dealt 2 pair in 5-card poker) - which would mean warming by 9+ degrees for some nations. The economic costs would be absolutely staggering.

But "sensible" people who don't want to be "extremist" about it focus on a binary choice - will it be the IPCC's median projection, or is it all bunk? Damn stupid way to do risk analysis.

Your calculations presuppose

Your calculations presuppose trust in those offering the probability estimates. That, however, is what is at issue.


What is AGW? Seems to be global warming, but what's the A?

Arthropogenic. Blame global

Arthropogenic. Blame global warming on the Lorenz butterfly. Sometimes misspelled as "anthropogenic".

One thing we know for sure . . .

If there is globing warming, the poor people will pay the price. If there is no global warming, the poor people will pay the price.