Is it cheaper to just let the planet heat?
Before getting into the debate that Jim Manzi and Brad Plumer are having on the costs of mitigating global warming, it's worth highlighting this bit from Manzi, which is slightly off-topic to the actual disagreement, but could be the most important thing you'll ever read:
The consensus scientific estimate is that there is a 1-in-10,000 chance of an asteroid large enough to kill a large fraction of the world’s population impacting the earth in the next 100 years. ... The U.S. government currently spends about four million dollars per year on asteroid detection (in spite of an estimate that one billion dollars per year spent on detection plus interdiction would be sufficient to reduce the probability of impact by 90 percent).
Why aren't we spending this money? Are we really that good at interdiction? If so, is it because of technology, or because of Bruce Willis?
As for the actual debate, Manzi argues that the likely costs of substantially reducing global warming emissions over the next century outweigh the likely costs of global warming over the next century. Plumer is less convinced, citing the possibility that global warming will be far worse than Manzi's numbers suggest; noting that environmental regulations have frequently been much more effective and less costly than naysayers predicted; and arguing that the distributional reality is that the costs of doing something fall heavily on developed nations but the costs of doing nothing fall heavily on undeveloped nations, and as such, we who've created the problem have a moral obligation to do something about it.
But they both ignore a point that's central to Manzi's argument: What happens after 100 years?
Letting greenhouse gases build in the atmosphere is a bit like letting a tree grow roots beneath the foundation of your house. It may not be that bad this year, or next year, or even the year after that. But with each year that goes by, the problem becomes incrementally more severe, and harder to reverse. So even if Manzi is right that the costs are manageable into 2100 -- a century, after all, is a long time for a human, but not for the atmosphere -- what does that do to our descendants who have to deal with a scorching planet between 2100 and 2200? And then into 2300, and then 2400?
I think Manzi's answer is that technology will save us by then. And maybe he's right. But maybe he's not. And if he's not, then we've let the problem become unimaginably bad for our descendants. If you bet on technology and you're wrong, it's not like we've got another of these planets waiting in the back somewhere.
The appropriate technological approach, it seems to me, is to pair a strategy of aggressive emissions reduction with a huge effort to develop technological solutions. Then, if the research begins to pay off, we can transition over to those technologies and ease up on the regulations. But if we don't so mitigation and instead trust in technology, we may let the situation get so bad that by the time we're ready to do mitigation, the problem is essentially irreversible.