No, wait. This isn’t yet another tedious post bashing Pruitt’s dumb ideas. It’s a post bashing mt2, which is far more interesting. I have two3 wildly exciting points to make about mt’s post at ATTP.
You people do need a red team
If you stick to science, you generally get it right1. Oddly enough; you are, after all, pretty well self-defined as “the side that gets the GW science right”. But you need to get out more. So when mt says Economic, social and environmental losses climb rapidly and nonlinearly with temperature change, and may already overwhelm the short-term benefits of fossil fuels, and will very likely do so in the near future, no-one blinks an eye. At best this is ambiguous and at worst it is wrong, so why is it only me that notices? Because, of course, you’re not actually looking for flaws in mt’s arguments. You’re just blipping along, la la la, damage from GW, yeah, we know that bit, eyes glaze over, words go straight out the other ear.
What is mt trying to say?
I don’t know. When I pointed out the problem, I got a reply-to-comment saying
My point is that the marginal cost of each additional unit of carbon emitted, which takes a very long time to accrue, may already exceed the marginal benefit of that unit, which is immediate. An economist might therefore conclude that I advocate an immediate abrupt cessation of all emissions. I readily stipulate that this is infeasible. I note that the aggregate cost of any action isn’t just determined by the marginal cost; and that cost of a given emission target is actually very trajectory dependent. But in terms of the long term aggregate well-being of the world, it’s quite plausible that we are already going backwards when we consume fossil fuels, and it’s almost certain that we eventually will be, and not in the too distant future.
I failed to parse that correctly in my reply there, since when correctly parsed it seems so wrong, but mt makes himself clear in a clarification on the psot:
UPDATE for clarification: Costs of a unit of emission aggregated over time may already overwhelm the benefits, which appear immediately. This balance shifts further against the value of emissions as geologically rapid climate change proceeds.
So he isn’t talking about “marginal” in terms of increases-in-emissions-over-present-emission-levels. He really does mean that each unit of CO2 emitted now may be doing more harm than good4. Pause to think about that. Suppose it is true. In which case, we should stop emitting it. Now; immeadiately. This would cause our civilisation to collapse, and billions would die. mt knows that isn’t possible; see, he even writes “I readily stipulate that this is infeasible”. But that means the other half of his assertion must be wrong: the marginal benefits, now, are greater than the future costs.
Is it possible that future damage from present-day emissions is so large that it dwarfs billions of deaths and the collapse of civilisation? That seems rather unlikely to me. Certainly, mt makes no attempt to provide evidence for his assertion. In evidence against, I’d put forward “typical” damage estimates of ~6% (of something; I forget what) by ~2100. That is a large number of billion dollars, of course.
Can we just stick to the science then please?
Sure. Providing you promise to say nothing about cost-benefit. But that does severely reduce your real-world relevance. You could try to argue “GW is obviously so bad that we should prevent it, rather than trying to assess the costs of preventing it against the benefits of preventing it”. And amongst nice people who agree that GW is bad, that’s a fine argument; everyone will take your word for it. But what about Bad People like Pruitt who don’t accept your argument?
1. Not if you’re Hawking, of course.
2. Not really, of course. Call it a vigorous test of his ideas. If ATTP’s moderation were faster, we could have the discussion over there, but it isn’t, so we can’t.
3. Sigh. Three.
4. Current thinking (see comment by MMM and my reply) is that mt does mean marginal changes to current emissions levels. And so the question to answer is the cost of one more or one less unit of CO2 emitted now, versus it’s future damage costs.