This is a really interesting post. The tail risks I’ve seen considered are generally tail warming scenarios, and once you frame it this way, it makes obviously more sense to focus on tail adaptation scenarios.
I am not sure I’m on board with using Lynas’s estimates to frame the debate. I agree we don’t have model evidence to base estimates off of, but 30-40% risk of civilizational collapse from 3 degrees seems absolutely insane to me. I could equally say that I estimate the probability at 100% and then say “well it’s probably somewhere in the middle”. Unreasonably large estimates shouldn’t be allowed to frame the discussion just because we can’t reject them with model evidence yet.
Here is some weak evidence that tail adaptation risk is not that high in median warming scenarios: the IPCC AR6 report does not emphasize tail risk from adaptation as having a modestly high probability, even though climate scientists are probably the most sympathetic to the idea that it does have a high probability. I’ll try to find an exact quote from it about the issue when I’m on my computer...
Thanks for your comments! Some very quick thoughts on your latter two points:
I agree that one should be careful with letting outlier estimates drive the discussion on what the correct estimate is. Nevertheless, I do think that highlighting Lynas’s estimate serves two particularly useful purposes here: it highlights that even an estimate this high is hard to concretely refute (as you noted), and it opens up the discussion of the wide range of intervening values (from the “standard” estimates of 1/10000 or 1/1000 all the way to, say, 1⁄10). While Lynas’s estimate might indeed be an outlier, I suspect that a substantial fraction within EA have estimates scattered across this range; you can still think that Lynas overestimated the risk by two whole orders of magnitude and that the “standard” EA estimates are too low.
I also agree with you that climate scientists might be more sympathetic than most to the idea of climate-change driven collapse at median levels of warming, and so the fact that they don’t really mention this in the literature is interesting. However I do suspect that this is primarily due to the difficulty of actually studying this using existing modeling frameworks (as discussed above) as well as the way in which “burden of proof” is typically interpreted in science (and especially in IPCC reports, where it seems to be unusually high). I think this makes it all the more important for EA folks to look at in more detail.
I wouldn’t put any weight on Lynas’ opinion. As I discussed in my review of his book, he argues that at 3C of warming, agriculture in the US would be completely destroyed. This is a gross misrepresentation of Glotter and Elliot. When I showed them Lynas’ interpretation, Joshua Elliot said “Wow. Yeah, that is definitely not the correct interpretation.” When I showed this to Lynas, he didn’t care.
This one misunderstanding alone is highly significant—he incorrectly thinks that the world’s second largest food producer will produce zero food at 3C. This is a clear misunderstanding. In fact, all of the projections that take into account likely agricultural progress suggest that US food production will increase over the 21st century despite climate change.
Yup, I totally agree it’s important for EA people to look at it in more detail. My impression was that IPCC reports survey expert priors, which do not have to be solely based on existing modelling frameworks, so I don’t know if that is a huge barrier. But I will defer to you on how the report is made.
I am not sure of the value of the two benefits you describe. If most experts had priors scattered fully over the range up to 30-40%, then I would be very shocked and would update my beliefs a lot. I just feel like most priors are very very far from this upper bound and that there is a false equivalence being implied by discussing this whole range.
Similarly, if the purpose is to show that a number can’t be concretely refuted, I don’t think that is valuable. The burden of proof is on someone making the claim, not vice versa. If I claim that the risk of human extinction this century is 80%, you would have a hard time concretely refuting me. But that wouldn’t lend any credence to my argument because I haven’t established it in any way.
My knee jerk reaction was also that 30-40% was an unreasonably high number, however, I kind of disagree with “Unreasonably large estimates shouldn’t be allowed to frame the discussion just because we can’t reject them with model evidence yet” since it’s hard to know what numbers are reasonable in the first place. It also provides a good starting point to the discussion and to challenge my assumptions on why I automatically want to reject the 30-40%.
This is a really interesting post. The tail risks I’ve seen considered are generally tail warming scenarios, and once you frame it this way, it makes obviously more sense to focus on tail adaptation scenarios.
I am not sure I’m on board with using Lynas’s estimates to frame the debate. I agree we don’t have model evidence to base estimates off of, but 30-40% risk of civilizational collapse from 3 degrees seems absolutely insane to me. I could equally say that I estimate the probability at 100% and then say “well it’s probably somewhere in the middle”. Unreasonably large estimates shouldn’t be allowed to frame the discussion just because we can’t reject them with model evidence yet.
Here is some weak evidence that tail adaptation risk is not that high in median warming scenarios: the IPCC AR6 report does not emphasize tail risk from adaptation as having a modestly high probability, even though climate scientists are probably the most sympathetic to the idea that it does have a high probability. I’ll try to find an exact quote from it about the issue when I’m on my computer...
Thanks for your comments! Some very quick thoughts on your latter two points:
I agree that one should be careful with letting outlier estimates drive the discussion on what the correct estimate is. Nevertheless, I do think that highlighting Lynas’s estimate serves two particularly useful purposes here: it highlights that even an estimate this high is hard to concretely refute (as you noted), and it opens up the discussion of the wide range of intervening values (from the “standard” estimates of 1/10000 or 1/1000 all the way to, say, 1⁄10). While Lynas’s estimate might indeed be an outlier, I suspect that a substantial fraction within EA have estimates scattered across this range; you can still think that Lynas overestimated the risk by two whole orders of magnitude and that the “standard” EA estimates are too low.
I also agree with you that climate scientists might be more sympathetic than most to the idea of climate-change driven collapse at median levels of warming, and so the fact that they don’t really mention this in the literature is interesting. However I do suspect that this is primarily due to the difficulty of actually studying this using existing modeling frameworks (as discussed above) as well as the way in which “burden of proof” is typically interpreted in science (and especially in IPCC reports, where it seems to be unusually high). I think this makes it all the more important for EA folks to look at in more detail.
I wouldn’t put any weight on Lynas’ opinion. As I discussed in my review of his book, he argues that at 3C of warming, agriculture in the US would be completely destroyed. This is a gross misrepresentation of Glotter and Elliot. When I showed them Lynas’ interpretation, Joshua Elliot said “Wow. Yeah, that is definitely not the correct interpretation.” When I showed this to Lynas, he didn’t care.
This one misunderstanding alone is highly significant—he incorrectly thinks that the world’s second largest food producer will produce zero food at 3C. This is a clear misunderstanding. In fact, all of the projections that take into account likely agricultural progress suggest that US food production will increase over the 21st century despite climate change.
Yup, I totally agree it’s important for EA people to look at it in more detail. My impression was that IPCC reports survey expert priors, which do not have to be solely based on existing modelling frameworks, so I don’t know if that is a huge barrier. But I will defer to you on how the report is made.
I am not sure of the value of the two benefits you describe. If most experts had priors scattered fully over the range up to 30-40%, then I would be very shocked and would update my beliefs a lot. I just feel like most priors are very very far from this upper bound and that there is a false equivalence being implied by discussing this whole range.
Similarly, if the purpose is to show that a number can’t be concretely refuted, I don’t think that is valuable. The burden of proof is on someone making the claim, not vice versa. If I claim that the risk of human extinction this century is 80%, you would have a hard time concretely refuting me. But that wouldn’t lend any credence to my argument because I haven’t established it in any way.
My knee jerk reaction was also that 30-40% was an unreasonably high number, however, I kind of disagree with “Unreasonably large estimates shouldn’t be allowed to frame the discussion just because we can’t reject them with model evidence yet” since it’s hard to know what numbers are reasonable in the first place. It also provides a good starting point to the discussion and to challenge my assumptions on why I automatically want to reject the 30-40%.
What makes 30-40% a better starting point than 90%? Or 5%?