Carbon, climate and other mysteries.

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Global-Warming Alarmists, You're Doing It Wrong

Megan McArdle is a Bloomberg View columnist. She wrote for the Daily Beast, Newsweek, the Atlantic and the Economist and founded the blog Asymmetrical Information. She is the author of "“The Up Side of Down: Why Failing Well Is the Key to Success.”
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Ask a Washington dinner party full of moderately well informed people what will happen with Iran over the next five years, and you’ll end up with a consensus that gee, that’s tough. Ask them what GDP growth will be in fall 2019, and they’ll probably converge on a hesitant “2 or 3 percent, I guess?” On the other hand, ask them what’s going to happen to the climate over the next 100 years, and what you’re likely to hear is angry.

How can one be certain about outcomes in a complex system that we’re not really all that good at modeling? Anyone who’s familiar with the history of macroeconomic modeling in the 1960s and 1970s will be tempted to answer “Umm, we can’t.” Economists thought that the explosion of data and increasingly sophisticated theory was going to allow them to produce reasonably precise forecasts of what would happen in the economy. Enormous mental effort and not a few careers were invested in building out these models. And then the whole effort was basically abandoned, because the models failed to outperform mindless trend extrapolation -- or as Kevin Hassett once put it, “a ruler and a pencil.”

Computers are better now, but the problem was not really the computers; it was that the variables were too many, and the underlying processes not understood nearly as well as economists had hoped. Economists can't run experiments in which they change one variable at a time. Indeed, they don't even know what all the variables are.

This meant that they were stuck guessing from observational data of a system that was constantly changing. They could make some pretty good guesses from that data, but when you built a model based on those guesses, it didn’t work. So economists tweaked the models, and they still didn’t work. More tweaking, more not working.

Eventually it became clear that there was no way to make them work given the current state of knowledge. In some sense the "data" being modeled was not pure economic data, but rather the opinions of the tweaking economists about what was going to happen in the future. It was more efficient just to ask them what they thought was going to happen. People still use models, of course, but only the unflappable true believers place great weight on their predictive ability.

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.

QuickTake Climate Change

If you’re not familiar with the lukewarmist case, I urge you to read the nine-part series  by Warren Meyer has written at Coyote Blog. I am not urging you to read it because I agree with every part. (In particular, I’m much more eager to ensure against even a small chance of climate catastrophe, just as I would support even a very expensive system to detect and deflect massive asteroids that might hit our planet. We’ve only got the one planet so far, and it would be a shame if something happened to it.)

But I urge you to read it because it is a calm, measured, very thoughtful laying out of the lukewarmist case by a very smart person who has put a lot of time and effort into thinking about the subject -- much more time and effort than 99 percent of the angry people on both sides who shout over dinner tables and type in all caps.

The series is also a model of how to talk about the subject. Meyer says “this is what I think, and this is why I think it.” People can certainly disagree with his conclusions, and I would be very interested to see climate bloggers engage with Meyer's series in like manner: refraining from calling names or questioning motives, and instead calmly laying out the reasons that they think warming is likely to be catastrophic.

But vanishingly little of the debate is conducted in those sorts of terms. Skeptics are accused of being ideologues, or in the pay of the fossil fuel industry, or simply selfish monsters who care nothing for future generations. The other side -- who expect big temperature jumps and catastrophic consequences -- are accused of being ideologues, or interested in making an alarmist case in order to further their own careers as climate change activists, or authoritarian monsters who are less interested in saving the planet than in forcing their own left-wing economic order on the rest of the world.

Many of these claims about motives are probably not entirely false -- it’s difficult to change your mind when you’ve built a career around a certain set of theories -- but they’re certainly not entirely true, and they’re largely beside the point. If Joseph Stalin tells you that the sky is blue, he’s right, even if he’s wrong about nearly everything else, and an authoritarian monster to boot.

The arguments about global warming too often sound more like theology than science. Oh, the word “science” gets thrown around a great deal, but it's cited as a sacred authority, not a fallible process that staggers only awkwardly and unevenly toward the truth, with frequent lurches in the wrong direction. I cannot count the number of times someone has told me that they believe in “the science,” as if that were the name of some omniscient god who had delivered us final answers written in stone. For those people, there can be only two categories in the debate: believers and unbelievers. Apostles and heretics.

This is, of course, not how science works, and people who treat it this way are not showing their scientific bona fides; they are violating the very thing in which they profess such deep belief.  One does not believe in “science” as an answer; science is a way of asking questions. At any given time, that method produces a lot of ideas, some of which are correct, and many of which are false, in part or in whole.  

There is a huge range of possible beliefs that go into assessing the various complicated theories about how the climate works, and the global-warming predictions generated by those theories range from “could well be catastrophic” to “probably not a big deal.” I know very smart, well-informed, decent people who fall at either end of the spectrum, and others who are somewhere in between. Then there are folks like me who aren’t sure enough to make a prediction, but are very sure we wouldn’t like to find out, too late, that the answer is “oops, catastrophic.”

These are not differences that can be resolved by name calling. 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.

Unfortunately, when you rally your own side with these sorts of tactics, you also rally the other tribe, and if they’re as numerous as you are, this can lead to defeat as easily as victory. It would be a lot better for everyone -- including the planet -- if we left off the tribalism and the excommunications and went back to actually talking about the science: messy, imprecise and always open for well-grounded debate.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

To contact the author of this story:
Megan McArdle at mmcardle3@bloomberg.net

To contact the editor responsible for this story:
Philip Gray at philipgray@bloomberg.net