Megan McArdle makes a point that should be obvious to anyone who either (1) has studied basic decison analysis or (2) was born with a little bit of common sense: you don’t make huge gambles for small gains, or risk big losses to avoid tiny ones. That she should have to make that point at all shows how utterly crazy her conservatarian friends have gotten on the topic of global warming. We’re not talking about some airy-fairy “precautionary principle” here; we’re talking about ordinary prudence.
Megan asks: If we had to give up 5% of GDP — a couple of years’ worth of growth — in order to avoid a big climate disaster, how painful would that be? And her answer is clearly the right one: not too painful at all, especially when you consider that no one proposes to give up that much of current GDP, but merely to slightly reduce the GDP growth we will experience going forward. From current prosperous-country levels of consumption, the marginal happiness-product of a little bit more stuff just isn’t that high. (Which also argues for policies to encourage the substitution of leisure for income, but that’s a different story.)
So it makes absolutely no sense to take a 5% risk of a 3° rise in average global temperature, an increase in extremes (more floods, more drought), an increase in storm activity, and a significant change in sea levels — not to mention real catastrophes like the shut-down of the deep convection current that drives the Gulf Stream — in order to avoid spending a couple of trillion dollars a year from a $65 trillion world GDP. (No, I don’t know that it would cost that much to avoid a disaster; let’s just assume it for the sake of the argument.)
Can any sane person claim that the risk of an extreme climate disaster if we continue to expand GHG emissions at current rates is less than 5%? If so, what the hell are we arguing about?
Of course the current scientific consensus might be wrong. But uncertainty actually argues for more precaution, not less. Current estimates could be wrong in either direction; that’s what “error band” means. At the end of the day, due to a positive feedback that wasn’t in the models, the actual impact of chlorofluorocarbons on the ozone layer turned out to be about three times the original estimate by Rowland and Molina that the chemical industry (and Bush the Elder) made such fun of.
So the argument against cap-and-trade or some similarly drastic global-warming control measures amounts to playing Russian Roulette because you can’t be absolutely sure all six chambers have bullets in them, and anyway the gun might misfire. Listening to the people who call themselves “global warming skeptics” is like listening to a five-year-old saying that it’s not treally important to look both ways before crossing the street because a car might not be coming.
No prudent CEO would bet his company on the off-chance that GHG emissions don’t cause global warming. But the candidates they give money to want us to bet our whole way of life on that proposition.
Yes, we could adapt to higher temperatures, higher sea levels, and more extreme weather; at least, we could do so much more easily than, say, Bangaladesh. And yes, if you don’t patch your roof when there’s a high likelihood of heavy rains you might get lucky and not get rained on, or you could always repair the water damage to your house and furniture and clothing and books. But only a lunatic would behave that way in real life. It’s scary that wanting to patch half the holes in the roof counts as “moderation” in politics.
Footnote Yes, John McCain — unusually, for a Republican — acknowledges the reality of the problem and even has endorsed a cap-and-trade plan, though he seems a trifle unclear on the concept of a cap. But that doesn’t mean that climate change isn’t on the ballot in November. When one candidate is pushing conservation and the other is making jokes about it and promising to drill for more and more oil you know which one is serious about the climate.