Daniel Reeves has written this reaction piece to my write-up of our bet.  I’m in blockquotes; he’s not.

By the way, I will be in Guatemala from November 11-16.  I’ll be doing a bunch of events at Universidad Francisco Marroquín on Friday, and speaking for the Mont Pelerin Society on Monday.  I’ll be at Tikal over the weekend.  If you see me in any of these places, please say hi!

Now here’s Daniel.

Bryan seems to start by acknowledging that 6 degrees of warming (we’re approaching 1 degree so far, for those just tuning in) would be devastating and that a 10% chance of that by the end of the century warrants mitigation efforts. He even acknowledges that — warming being proportional to cumulative historical emissions — we can’t afford to wait. Assuming that that 10% is correct. And then the core of his argument is that that 10% must not be remotely correct because of how biased the authors of Climate Shock must be to be writing an alarmist climate change book, good as it is for an alarmist climate change book.

This feels frustrating to me because it sounds like: “I disbelieve this book because the authors are so biased. How do I know they’re biased? They wrote an alarmist climate change book!”

The whole point is to assess whether the alarmism is correct. If you dismiss the authors for the very fact that they think alarmism is correct then you are fundamentally closed-minded on this issue and probably shouldn’t have accepted the bet. (To be clear, I’ve paid up already.)

My point-by-point replies follow:

1. Wagner and Weitzman place huge weight on the “fat tails” of climate disaster, and fixate on a 10% chance of hitting 6°C global warming.

I mildly object to “fixate” here. I would call it bending over backwards to be as non-alarmist as possible, focusing on the unambiguously devastating tail risk and minimizing quibbling about the potentially confusing mix of costs and benefits of milder warming.

a. I’m not remotely surprised that Wagner and Weitzman say there is a 10% chance of disaster. Given that they’re writing a book about climate change, I actually expected a higher probability.

This sounds like assuming bad faith. My sense from the book was that the authors were incredibly conscientious and intellectually honest. But maybe I’m misunderstanding you and you’re agreeing that it’s impressive that the authors resisted the temptation to exaggerate the probability?

b. I’m not qualified to assess the research underlying this probability, but I suspect that it is overestimated because (a) predictions of disaster are almost always wrong, and (b) climate experts have a strong and obvious left-wing bias.

Yes, the politicization of this topic is infuriating. See Scott Alexander’s delightful alternate-universe synopsis of climate change being politicized in the opposite direction.

But this is why I was so hopeful about you reading Wagner and Weitzman’s book. It doesn’t seem to me to have too much left-wing bias.

(Also some of the bias is trying to counteract the other side’s bias, which is what turns the whole topic into an epistemic nightmare. I don’t think you can just pin all the bias on the left. Isn’t there even greater right-wing bias to rationalize business-as-usual?)

But let’s rise above all that and just try to understand what’s true. In that spirit, it’s fair to do the Bayesian updating from your skeptical priors but maybe you could clarify how far the book shifts those priors?

c. Furthermore, it is quite clear that climate experts were heavily left-wing long before they started studying climate. So it is hardly surprising that the smartest people working in this area are so pessimistic. They started with a more talented team of advocates.

Counterpoint: The famous Exxon report from the 80s that perfectly predicted our current 1-degree warming.

d. Wagner and Weitzman don’t consider the total disasters that might result from aggressive climate policy. Like what? Most obviously, their policies keep the world poor, hence war-prone, for many extra decades. Which in turn raises the probability of World War III before 2100 from say 10% to 15%.

Some policy interventions — say, funding carbon capture — don’t have that possible failure mode.

Side note: I think Pigouvian taxes should be philosophically fundamental to laissez faire capitalism (by maximizing how much faire we can laissez) and that we want a carbon tax even if — in light of geoengineering? — it’s lower than Wagner and Weitzman recommend. I also disagree that Pigouvian taxes are fundamentally impoverishing. I’m a fan of revenue-neutral carbon taxes.

2. Wagner and Weitzman are extremely optimistic about geoengineering, yet childishly reject it. […] Why childish? Because when they actually discuss the evidence on geoengineering, it’s far more solid than “an experimental lung cancer drug treatment that showed some promise in a lab.”

Wait, can I still win this bet on a technicality if Wagner and Weitzman inadvertently convinced you that we should pursue stratospheric aerosol injection (what they mostly mean by geoengineering in the book)? I don’t know how serious I am with that question but I’d love to understand your thinking more!

In the meantime, I’ve read a persuasive-sounding pitch for geoengineering by David Keith, which also explains why we should think of it as a last resort. From that plus my recollection from Climate Shock:

  1. Geoengineering doesn’t mitigate ocean acidification
  2. It worsens air pollution
  3. It increases climate variance and extreme weather events
  4. It damages the ozone layer
  5. Unknown unknowns

It’s probably especially important to take #5 seriously. I definitely didn’t get the impression that Wagner and Weitzman were being childish about this, even if they’re ultimately wrong about geoengineering.

Frankly, it looks like Wagner and Weitzman want to impoverish the world by many extra trillions of dollars to ensure that humanity’s savior is the United Nations instead of the United States or (horrors!) Elon Musk.

This is Bulverism!

3. Wagner and Weitzman barely mention nuclear power or the absurd regulatory burden under which it labors. This fits with the Social Desirability Bias story, and makes me further distrust them.

I may be more trusting than you but I’d only have distrusted them on those grounds if they’d argued against nuclear energy. Wagner and Weitzman think policy intervention should be limited to carbon taxes. Nuclear energy doesn’t emit carbon so they are implicitly pro-nuclear. I’m sure they’d agree about the absurd regulatory burden as well. They do spend a lot of time in the book on the absurdity of the current fossil fuel subsidies, which I’m sure you also despise.