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:
Climate change is real and its impacts are mostly negative, but common portrayals of devastation are unfounded. Scenarios set out under the UN Climate Panel (IPCC) show human welfare will likely increase to 450% of today’s welfare over the 21st century. Climate damages will reduce this welfare increase to 434%.
Arguments for devastation typically claim that extreme weather (like droughts, floods, wildfires, and hurricanes) is already worsening because of climate change. This is mostly misleading and inconsistent with the IPCC literature. For instance, the IPCC finds no trend for global hurricane frequency and has low confidence in attribution of changes to human activity, while the US has not seen an increase in landfalling hurricanes since 1900. Global death risk from extreme weather has declined 99% over 100 years and global costs have declined 26% over the last 28 years.
Arguments for devastation typically ignore adaptation, which will reduce vulnerability dramatically. While climate research suggests that fewer but stronger future hurricanes will increase damages, this effect will be countered by richer and more resilient societies. Global cost of hurricanes will likely decline from 0.04% of GDP today to 0.02% in 2100.
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.
Climate policies also have costs that often vastly outweigh their climate benefits. The Paris Agreement, if fully implemented, will cost $819–$1,890 billion per year in 2030, yet will reduce emissions by just 1% of what is needed to limit average global temperature rise to 1.5°C. Each dollar spent on Paris will likely produce climate benefits worth 11¢.
Long-term impacts of climate policy can cost even more. The IPCC’s two best future scenarios are the “sustainable” SSP1 and the “fossil-fuel driven” SSP5. Current climate-focused attitudes suggest we aim for the “sustainable” world, but the higher economic growth in SSP5 actually leads to much greater welfare for humanity. After adjusting for climate damages, SSP5 will on average leave grandchildren of today’s poor $48,000 better off every year. It will reduce poverty by 26 million each year until 2050, inequality will be lower, and more than 80 million premature deaths will be avoided.
Using carbon taxes, an optimal realistic climate policy can aggressively reduce emissions and reduce the global temperature increase from 4.1°C in 2100 to 3.75°C. This will cost $18 trillion, but deliver climate benefits worth twice that. The popular 2°C target, in contrast, is unrealistic and would leave the world more than $250 trillion worse off.
The most effective climate policy is increasing investment in green R&D to make future decarbonization much cheaper. This can deliver $11 of climate benefits for each dollar spent.
More effective climate policies can help the world do better. The current climate discourse leads to wasteful climate policies, diverting attention and funds from more effective ways to improve the world.
Is Lomborg right?
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.
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.
Nobody really knows.
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.
I don’t think nuclear power is currently a cost-effective approach to mitigating global warming. It only really makes sense when geopolitical concerns are a factor, eg threats to tankers transporting LNG to Europe or Japan.
Elaborate? Assuming there were no political blockers, why is it not cost effective? Is it because the energy output of a plant is limited by how far the energy can travel, and therefore you’d need many plants?
Regulation is probably the main reason. See, for example, https://www.instituteforenergyresearch.org/nuclear/regulations-hurt-economics-nuclear-power/.
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.
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/
If it’s been hotter historically, such that dinosaurs would have been totally fine with these higher temperatures that doesn’t exactly help humans...
Currently lots of the Earth is too cold to live in. In a warmer Earth those places would become habitable even as other places became too hot.