I think most climate scientists do not predict human extinction from warming
I very much agree, and guess Toby’s and Will’s estimates for the existential risk from climate change are much higher than the median expert’s guess for the risk of human extinction from climate change. Toby guessed an existential risk from climate change from 2021 to 2120 of 0.1 %. Richards et al. (2023) estimates “∼6 billion deaths [they say “∼5 billion people” elsewhere] due to starvation by 2100″ for a super unlikely “∼8–12 °C+” of global warming by then, and I think they hugely overestimated the risk. Most importantly, they assumed land use and cropland area to be constant.
Yeah, I think I recall David Thorstad complaining that Ord’s estimate was far too high also.
Be careful not to conflate “existential risk” in the special Bostrom-dervied definition that I think Ord, and probably Will as well, are using with “extinction risk” though. X-risk from climate *can* be far higher than extinction risk, because regressing to a pre-industrial state and then not succeeding in reindustrialising (perhaps because easily accessible coal has been used up), counts as an existential risk, even though it doesn’t involve literal extinction. (Though from memory, I think Ord is quite dismissive of the possibility that there won’t be enough accessible coal to reindustrialise, but I think Will is a bit more concerned about this?)
Thanks for the clarification, David. There are so many concepts of existential risk, and they are often so vague that I think estimates of existential risk can vary by many orders of magnitude even holding constant the definition in words of a given author. So I would prefer discussions to focus on outcomes like human extinction which are well defined, even if their chance remains very hard to estimate.
I also think human extinction without recovery to a similarly promising state is much less likely than human extinction. For a time from human extinction to that kind of recovery described by an exponential distribution with a mean of 66 M years, which was the time from the last mass extinction until humans evolving, and 1 billion years during which the Earth will remain habitable, and therefore recovery is possible, the probability of recovery conditional on human extinction would be 2.63*10^-7 (= e^(-10^9/(66*10^6))).
Thanks for the discussion, David and Manuel.
I very much agree, and guess Toby’s and Will’s estimates for the existential risk from climate change are much higher than the median expert’s guess for the risk of human extinction from climate change. Toby guessed an existential risk from climate change from 2021 to 2120 of 0.1 %. Richards et al. (2023) estimates “∼6 billion deaths [they say “∼5 billion people” elsewhere] due to starvation by 2100″ for a super unlikely “∼8–12 °C+” of global warming by then, and I think they hugely overestimated the risk. Most importantly, they assumed land use and cropland area to be constant.
Yeah, I think I recall David Thorstad complaining that Ord’s estimate was far too high also.
Be careful not to conflate “existential risk” in the special Bostrom-dervied definition that I think Ord, and probably Will as well, are using with “extinction risk” though. X-risk from climate *can* be far higher than extinction risk, because regressing to a pre-industrial state and then not succeeding in reindustrialising (perhaps because easily accessible coal has been used up), counts as an existential risk, even though it doesn’t involve literal extinction. (Though from memory, I think Ord is quite dismissive of the possibility that there won’t be enough accessible coal to reindustrialise, but I think Will is a bit more concerned about this?)
Thanks for the clarification, David. There are so many concepts of existential risk, and they are often so vague that I think estimates of existential risk can vary by many orders of magnitude even holding constant the definition in words of a given author. So I would prefer discussions to focus on outcomes like human extinction which are well defined, even if their chance remains very hard to estimate.
I also think human extinction without recovery to a similarly promising state is much less likely than human extinction. For a time from human extinction to that kind of recovery described by an exponential distribution with a mean of 66 M years, which was the time from the last mass extinction until humans evolving, and 1 billion years during which the Earth will remain habitable, and therefore recovery is possible, the probability of recovery conditional on human extinction would be 2.63*10^-7 (= e^(-10^9/(66*10^6))).