Bryan Caplan  

Questions for Arnold

Standards of Proof... Pushback on my Skepticism...

1. Arnold writes:

I have no strong priors about the distribution of possible global temperatures going forward.
How about strong posteriors conditional upon the existence of a scientific consensus? If consensus doesn't impress you, then you should be willing to bet at even odds that temperature will fall.

2. Arnold adds:

My skepticism is about the effect of man-made CO2 on global warming. If Bryan or anyone else can devise a bet that focuses on that parameter, then that would allow me to put money on my skepticism.
What's the problem with conditional bets? We could bet on (a) Temperature will rise conditional on CO2 emissions being above a certain level, and (b) Temperature will rise conditional on CO2 emissions being below that level. I don't know enough climatology to specify reasonable cutpoints. But conceptually, what's the problem?

3. Arnold observes:

Gregory Clark wants to argue that in the 1800's British workers were much more productive than Indian workers. He asks that if British and Indian workers were close substitutes, why would you ship cotton from India to Britain, turn it into cloth, and ship the cloth back to India? Instead, if they were close substitutes, you would observe English companies building cloth factories in India in order to serve the Indian market more cheaply. In other words, shipping cotton to England and cloth back to India is something that is unlikely to occur if workers are close substitutes. Instead, it provides evidence, meeting my "strangely strict" standards, that British workers were more productive.
I agree that this is a fine argument. But it only works because we have a large body of diverse pieces of evidence that (a) Businesses want to make money; (b) Businesses are not run by idiots; (c) Cotton made in England is a close substitute for cotton made in India; (d) Economic historians are not making up these stylized facts; etc. Clark's argument is good, but it's far from "an experiment or a naturally-occurring event where the results are extremely unlikely to occur unless X is true." Isn't it?

Comments and Sharing

COMMENTS (5 to date)
John S Bolton writes:

No cotton was made, it was grown in India but not in England. Is cotton thread what is meant? British manufacturers could have set up their sort of production in the parts of India controlled by Britain, and eventually they did. In India hand production had to remain long dominant, since why we would you use mechanization so long as there is effectively limitless supply of labor employable at physiological subsistence, or very close to it? The productivity using mechanization needed to be continually higher, tenfold at one time, 100-fold at another point, before you would introduce such mechanization that was in use in Britain, into India. Otherwise you do mechanization for its own sake, leaving needy workers without jobs which they could have done less productively, but as cheaply overall, relative to how it was done in the high-wage country.

Bruce G Charlton writes:

I agree that opinions should be backed-up with a 'sincerity tax' (as WD Hamilton called it) - but betting is only one very specific and artificial behavioural measure of sincerity.

The way you lead your life, and the choices you make, are another kind of bet. The climate change professionals are betting *not* that anthropogenic CO2 is a reversible cause of global warming - but that they can make a living out of these ideas for the medium term. Hence the lavish lifestyles and private jet flights to climate conferences. The actions say something different from the words.

Climate skeptics could be betting with their lives agaisnt any one of this chain of propositions - they might even believe that anthropogenic CO2- induced global warming will be a very rapid and severe problem - but that this process is irreversible (this is more or less Lovelock's view, although I think he regards methane as the main culprit).

The main area of disagreement about climate change is whether the best policy strategy is pro-growth or anti-growth - do we try to expand human capability to solve the problem (whether or not it happens), or reduce the size of the problem by diminishing human impact?

My point is that bets are merely one form of sincerity test. Of course measuring sincereity may or may not be useful or interesting. But economics is based on taking seriously what people do, rather than on polling their advertized beliefs.

Rather than focusing on betting, or on polls, we need to develop economic type measures of what people really believe about climate change, based on their real life choices.

John Thacker writes:

But conceptually, what's the problem?

The bet may not be extremely useful if Professor Kling believes that (a) There is a high probability of man-made CO_2 concentrations rising and (b) There is a high probability of the temperature rising, but that (a) does not cause (b), and restricting (a) (even if possible, though it may seem unlikely) would not solve the problem. One could make a bet that even if made-made CO_2 is restricted, then temperatures will still rise, though that's still a low probability event in Professor Kling's mind. A bet where the skeptic takes an event that he thinks has a low probability and gets a large payoff is unusual to my mind.

That (a) has happened and (b) has happened is, I think, well-established. The body of diverse evidence demonstrate this. That they have caused each other is, as always, somewhat harder to prove though certainly plausible because of the obvious mechanism.

John Thacker writes:

The plus side of the conditional bet for Professor Kling, though, is that it would hedge appropriately. It seems to me that many such bets are somewhat less useful for skeptics. Having a bet that pays off only if global catastrophe does not occur, and requires one to lose money if catastrophe (that will affect oneself as well) increases risk. It's an anti-hedge.

Therefore, one should predict that skeptics should be less likely to take "normal" predictive bets, where they win if the negative event does not occur, than their personal probabilities would indicate, and that the odds they offer should not quite reflect their true belief.

bt writes:

From a layman's perspective (non-economist), being made a colony was brutal process. After all we revolted against this practice in our own history. In any review of British practices let's acknowledge other important variables (democracy, freedom of assembly, speech, Ghandi, etc.) at play rather than simple economics.

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