I think the reviewer may be concluding from the above that, given no international food trade, calorie consumption would be much lower, and therefore increasing food production via new food sectors would become much more important relative to distribution. I agree with the former, but not the latter. Loss of international food trade is more of a problem of food distribution than production. If this increased thanks to new food sectors, but could not be distributed to low-income food-deficit countries (LIFDCs) due to loss of trade, there would still be many famine deaths there. Many LIFDCs are in tropical regions too, where there is a smaller decrease in crop yields during a nuclear winter (see Fig. 4 of Xia 2022).
Another factor is that if countries are aware of the potential of scaling up resilient foods, they would be less likely to restrict trade. Therefore, I’m thinking the outcomes might be fairly bimodal, with one scenario of resilient food production and continued trade, and another scenario of not having resilient food production and loss of trade, potentially more than just food trade, perhaps with loss of industrial civilization or worse.
Yet, at least ignoring anthropics, I believe there would be a probability of full recovery of 100 % (= 1 - e^(-10^9/(66*10^6))) even then, assuming:
An exponential distribution for the time to go from i) human extinction due to such an asteroid to ii) evolving a species as capable as humans at steering the future, with mean equal to the aforementioned 66 M years.
The above evolution could take place in the next 1 billion years during which the Earth will remain habitable.
I think this assumes a scenario where, after the asteroid that causes human extinction, the next billion years are large asteroid/comet free, which is not a good assumption.
Another factor is that if countries are aware of the potential of scaling up resilient foods, they would be less likely to restrict trade. Therefore, I’m thinking the outcomes might be fairly bimodal, with one scenario of resilient food production and continued trade, and another scenario of not having resilient food production and loss of trade, potentially more than just food trade, perhaps with loss of industrial civilization or worse.
I agree that is a factor, but I guess the distribution of the severity of catastrophes caused by nuclear war is not bimodal, because the following are not binary:
Awareness of mitigation measures:
More or less countries can be aware.
Any given country can be more or less aware.
Ability to put in practice the mitigation measures.
Export bans:
More or less countries can enforce them.
Any given country can enforce them more or less.
In addition, I have the sense historical more local catastrophes are not bimodal, following distributions which more closely resemble a power law, where more extreme outcomes are increasingly less likely.
I think this assumes a scenario where, after the asteroid that causes human extinction, the next billion years are large asteroid/comet free, which is not a good assumption.
Good point! I have updated the relevant bullet in the post:
So Toby would expect an asteroid impact similar to that of the last mass extinction to be an existential catastrophe. Yet, at least ignoring anthropics, I believe the probability of not fully recovering would only be 0.0513 % (= e^(-10^9/(132*10^6))), assuming:
An exponential distribution with a mean of 132 M years (= 66*10^6*2) represents the time to go from i) human extinction due to such an asteroid to ii) evolving a species as capable as humans at steering the future. I supposed this on the basis that:
An exponential distribution with a mean of 66 M years describes the time between extinction threats as well as that to go from i) to ii) conditional on no extinction threats.
Given the above, extinction and full recovery are equally likely. So there is a 50 % chance of full recovery, and one should expect the time until full recovery to be 2 times (= 1⁄0.50) as long as that conditional on no extinction threats.
The above evolution could take place in the next 1 billion years during which the Earth will remain habitable.
Now the probability of not fully recovering is 0.0513 %, i.e. 1.95 k (= 5.13*10^-4/(2.63*10^-7)) times as high as before. Yet, the updated unconditional existential risk (extinction caused by the asteroid and no full recovery afterwards) is still astronomically low, 3.04*10^-15 (= 5.93*10^-12*5.13*10^-4). So my point remains qualitatively the same.
I have also added the 2nd sentence in the following bullet:
Even if nuclear war causes a global civilisational collapse which eventually leads to extinction, I guess full recovery would be extremely likely. In contrast, an extinction caused by advanced AI would arguably not allow for a full recovery.
Another factor is that if countries are aware of the potential of scaling up resilient foods, they would be less likely to restrict trade. Therefore, I’m thinking the outcomes might be fairly bimodal, with one scenario of resilient food production and continued trade, and another scenario of not having resilient food production and loss of trade, potentially more than just food trade, perhaps with loss of industrial civilization or worse.
I think this assumes a scenario where, after the asteroid that causes human extinction, the next billion years are large asteroid/comet free, which is not a good assumption.
Thanks for the comments, David.
I agree that is a factor, but I guess the distribution of the severity of catastrophes caused by nuclear war is not bimodal, because the following are not binary:
Awareness of mitigation measures:
More or less countries can be aware.
Any given country can be more or less aware.
Ability to put in practice the mitigation measures.
Export bans:
More or less countries can enforce them.
Any given country can enforce them more or less.
In addition, I have the sense historical more local catastrophes are not bimodal, following distributions which more closely resemble a power law, where more extreme outcomes are increasingly less likely.
Good point! I have updated the relevant bullet in the post:
Now the probability of not fully recovering is 0.0513 %, i.e. 1.95 k (= 5.13*10^-4/(2.63*10^-7)) times as high as before. Yet, the updated unconditional existential risk (extinction caused by the asteroid and no full recovery afterwards) is still astronomically low, 3.04*10^-15 (= 5.93*10^-12*5.13*10^-4). So my point remains qualitatively the same.
I have also added the 2nd sentence in the following bullet: