This is a linkpost for https://www.sciencedirect.com/science/article/pii/S0040162520304157
Lomborg is massively overconfident in his predictions but not exactly less wrong than the implicit mainstream view that the economic impacts will definitely be ruinous enough to justify expensive policies.
It's very hard to know, the major problem is just that the existing climate econ models make so many simplifying assumptions that they're near-useless except for giving pretty handwavy lower bounds on damage, especially when the worst risks to worry about are in correlated disasters and tail risks, and Lomborg makes the mistake of taking them completely literally. I discussed this at length a couple of years ago and John Halstead later wrote a book-length report on what the climate impacts literature can and can't tell us.
Global cost of hurricanes will likely decline from 0.04% of GDP today to 0.02% in 2100.
I don't think that's correct, but that's also an odd thing to focus on. There's glaciers melting, ocean acidification, forest and peat fires, heatwaves in India, and various other things. I think we've already seen some significant rainfall pattern changes; nobody really knows how they'll end up, but things were set up based on existing ones, so change would generally cause some issues.
Climate-economic research shows that the total cost from untreated climate change is negative but moderate, likely equivalent to a 3.6% reduction in total GDP.
Nobody really knows.
The popular 2°C target, in contrast, is unrealistic and would leave the world more than $250 trillion worse off.
World CO2 emissions were ~37B tons last year. Complete mitigation would be ~$70/ton if done intelligently. That's ~$2.6T/year.
Marine cloud brightening is quite possibly worth doing, but the more of it you do the less cost-effective it is, and it obviously doesn't do anything about ocean acidification.
'If done intelligently' is really one hell of an 'if'.
Yes, intelligent climate change mitigation strategies would not cost very much. (On some assumptions about nuclear power, intelligent climate change mitigation strategies might have negative cost).
But the more relevant question is the cost of the climate change mitigation strategies we actually get.
Arguments for devastation typically ignore adaptation, which will reduce vulnerability dramatically.
I think this is an important crux, and one that I believe. Most argument about climate change seem to assume it will just happen to us without any response other than to try to keep things exactly how they are in the face of changing weather. But obviously that's not what will happen because it never happens except in isolated pockets. In general, people find ways to adapt to their circumstances.
For what it's worth, the other crux I have in not worrying too much about climate change is that even the worst realistic forecasts don't make Earth's climate move outside its historical distribution. Humans have lived during one of Earth's colder period, but historically it's been a lot hotter. Our bodies are well adapted for heat (so long as we can cool off using sweat) and cold (so long as there's a source of fuel for fire and material to make clothes from), so it would take climate shifts beyond what's typically predicted to get outside the range of what humans seem able to adapt to.
I don't know Lomborg is right about other claims, although given the above I don't think it matters much.
Humans have lived during one of Earth's colder period, but historically it's been a lot hotter. Our bodies are well adapted for heat (so long as we can cool off using sweat)
This doesn't seem very reassuring? For example, https://climate.nasa.gov/explore/ask-nasa-climate/3151/too-hot-to-handle-how-climate-change-may-make-some-places-too-hot-to-live/
...Since 2005, wet-bulb temperature values above 95 degrees Fahrenheit [35 C] have occurred for short periods of time on nine separate occasions in a few subtropical places like Pakistan and the Persian Gulf. T
I think this is somewhat reasonable, but also I think that a lot of facts in this quote have been selected to be misleading, so I have a personal distrust of this guy.
E.g. singling out hurricanes rather than drought, wildfire, floods, or heat waves (not even mentioned) - why do you think hurricanes were chosen? https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-11/ Turns out it could have been floods too - those have been moving around but not getting worse on average. The other things are getting worse though.
Paris agreement compared to "amount needed to limit warming to 1.5C" rather than to a more clear number (Is limiting warming to 1.5C even physically possible now? Would it need to be a reduction so large it puts us far in the negatives of carbon emitted, thus making the "1%" number technically correct?)
@Fluttershy did some investigation into Lomborg a while back, not sure how clarifying it was though. Resolved that Lomborg frequently lies.
An important thing that this analysis leaves out is the uncertainty regarding feedback loops. If e.g. warming causes permafrost to melt and release more greenhouse gasses, there is a possibility of a runaway process that results in catastrophic warming. We don't know how bad the tail risks are, and an analysis that looks at the median case doesn't address that issue.
It seems like that analysis doesn't include large-scale crop failures, which is one of the worst anticipated downsides of climate change. It also doesn't account for the non-death loss of welfare involved in suffering through heatwaves and other extreme weather events, and worrying about the next one. That's not to argue against this whole line of analysis, just to note that it's incomplete.
I recently came across Bjorn Lomborg’s 2020 article Welfare in the 21st century: Increasing development, reducing inequality, the impact of climate change, and the cost of climate policies. It runs counter to many things I have heard about climate change. For example, it contains the below chart, which I found very surprising:
The abstract reads:
Is Lomborg right?