This lesson from economics is essentially what the “lukewarmists” bring to discussions about climate change. They concede that all else equal, more carbon dioxide will cause the climate to warm. But, they say that warming is likely to be mild unless you use a model which assumes large positive feedback effects. Because climate scientists, like the macroeconomists, can’t run experiments where they test one variable at a time, predictions of feedback effects involve a lot of theory and guesswork. I do not denigrate theory and guesswork; they are a vital part of advancing the sum of human knowledge. But when you’re relying on theory and guesswork, you always want to leave plenty of room for the possibility that your model’s output is (how shall I put this?) … wrong.
Naturally, proponents of climate-change models have welcomed the lukewarmists’ constructive input by carefully considering their points and by advancing counterarguments firmly couched in the scientific method.
No, of course I’m just kidding. The reaction to these mild assertions is often to brand the lukewarmists “deniers” and treat them as if what they were saying was morally and logically equivalent to suggesting that the Holocaust never happened.
Nor has the presumed object of this name calling — to delegitimize thoughtful opposition, and thereby increase the consensus in favor of desired policy proposals — been a notable political success, at least in the U.S. It has certainly rallied the tribe, and produced a lot of patronizing talk about science by people who aren’t actually all that familiar with the underlying scientific questions. Other than that, we remain pretty much where we were 25 years ago: holding summits, followed by the dismayed realization that we haven’t, you know, really done all that much except burn a lot of hydrocarbons flying people to summits.
Maybe last year’s Paris talks will turn out to be the actual moment when things started to change — but having spent the last 15 years as a reporter listening to people tell me that no, really, we’re about to turn the corner, I retain a bit of skepticism.