In addition to this, there was a post on LessWrong pointing out that the nuclear winter agricultural impacts studies carried out by Robock Toon and others was based on the assumption that humans take no adaptive response to global cooling of ten degrees C. This study found 5 billion dead, but this is an obvious overestimate for a realistic response to massive global cooling. I suspect the death estimates they give are out by at least two orders of magnitude, given the various unrealistic assumptions they use
Preliminary results from ALLFED suggest that (see Fig. 1), in a 150 Tg scenario[1] without food trade, stopping the consumption of animals and biofuels, reducing waste, and rationing stored food[2] would increase calorie supply by a factor of 3 (= 0.63/0.19). On the other hand, “failure of electrical grids, transportation infrastructure, telecommunications, or other infrastructure destruction due to the nuclear war is not considered” (neither in ALLFED’s preliminary results nor Xia 2022).
This study found 5 billion dead, but this is an obvious overestimate for a realistic response to massive global cooling. I suspect the death estimates they give are out by at least two orders of magnitude, given the various unrealistic assumptions they use
50 million dying from starvation (more than 50 million would die from the direct impacts of the nuclear war) is possible with a ~90% reduction in non-adapted agriculture (with current applications of fertilizers, pesticides, etc), but trade, resilient foods, and subsidies would have to go very well. I have significant probability mass for current awareness and preparation on most of all trade (not just food trade) breaking down with loss of industry in most areas, and significantly greater than 5 billion dead. This is partly because in overshoot scenarios, population can go to significantly below the equilibrium due to people “eating the seed corn.”
Thanks for clarifying. If instead one uses a mean (though I do think the tails should be weighted more heavily) closer to Luisa’s and my analysis of 30 Tg, then Xia predicts about 1.6 billion starvation fatalities and about 110 million direct fatalities (though this latter number would probably be higher because Xia assumes that all areas hit would firestorm, which I don’t, so I think more area would be hit to produce that amount of soot to the stratosphere). This is pessimistic in that it assumes no international food trade, no planting location adaptation, limited response in biofuels and animals, stored food runs out in a year, and no resilient foods. However, it is optimistic in assuming food only goes to the people who would survive. The extreme case would be if there is not enough food to go around, if the food is shared equally, then everyone would die. “Eating the seed corn” means that desperate people would eat the seeds and not be able to grow food in the future. This could apply to eating wild animals including fish to extinction, and then not being able to have food in the future. The Xia number is also optimistic in assuming that nonfood trade will continue, such that countries will still have the agricultural equipment, fuel, fertilizers, pesticides, etc. to produce the crops. There is also the chance of losing cooperation within countries, significantly increasing mortality. For instance, if farming is lost, there would be around 99.9% mortality returning to hunting and gathering with the current climate, worse in nuclear winter conditions (assuming we can figure out how to revert to hunting and gathering, which is not guaranteed). Overall, I think we should have large uncertainties in the response to a shock of this magnitude.
In addition to this, there was a post on LessWrong pointing out that the nuclear winter agricultural impacts studies carried out by Robock Toon and others was based on the assumption that humans take no adaptive response to global cooling of ten degrees C. This study found 5 billion dead, but this is an obvious overestimate for a realistic response to massive global cooling. I suspect the death estimates they give are out by at least two orders of magnitude, given the various unrealistic assumptions they use
Thanks for noting that, John!
Preliminary results from ALLFED suggest that (see Fig. 1), in a 150 Tg scenario[1] without food trade, stopping the consumption of animals and biofuels, reducing waste, and rationing stored food[2] would increase calorie supply by a factor of 3 (= 0.63/0.19). On the other hand, “failure of electrical grids, transportation infrastructure, telecommunications, or other infrastructure destruction due to the nuclear war is not considered” (neither in ALLFED’s preliminary results nor Xia 2022).
The one for which Xia 2022 report 5 billion deaths.
Xia 2022 assumes “all stored food is consumed in Year 1”.
50 million dying from starvation (more than 50 million would die from the direct impacts of the nuclear war) is possible with a ~90% reduction in non-adapted agriculture (with current applications of fertilizers, pesticides, etc), but trade, resilient foods, and subsidies would have to go very well. I have significant probability mass for current awareness and preparation on most of all trade (not just food trade) breaking down with loss of industry in most areas, and significantly greater than 5 billion dead. This is partly because in overshoot scenarios, population can go to significantly below the equilibrium due to people “eating the seed corn.”
I was thinking of all of the assumptions, i.e. about the severity of the winter and the adaptive response.
Sorry if I’m being thick, but what do you mean by ‘eating the seed corn’ here?
Thanks for clarifying. If instead one uses a mean (though I do think the tails should be weighted more heavily) closer to Luisa’s and my analysis of 30 Tg, then Xia predicts about 1.6 billion starvation fatalities and about 110 million direct fatalities (though this latter number would probably be higher because Xia assumes that all areas hit would firestorm, which I don’t, so I think more area would be hit to produce that amount of soot to the stratosphere). This is pessimistic in that it assumes no international food trade, no planting location adaptation, limited response in biofuels and animals, stored food runs out in a year, and no resilient foods. However, it is optimistic in assuming food only goes to the people who would survive. The extreme case would be if there is not enough food to go around, if the food is shared equally, then everyone would die. “Eating the seed corn” means that desperate people would eat the seeds and not be able to grow food in the future. This could apply to eating wild animals including fish to extinction, and then not being able to have food in the future. The Xia number is also optimistic in assuming that nonfood trade will continue, such that countries will still have the agricultural equipment, fuel, fertilizers, pesticides, etc. to produce the crops. There is also the chance of losing cooperation within countries, significantly increasing mortality. For instance, if farming is lost, there would be around 99.9% mortality returning to hunting and gathering with the current climate, worse in nuclear winter conditions (assuming we can figure out how to revert to hunting and gathering, which is not guaranteed). Overall, I think we should have large uncertainties in the response to a shock of this magnitude.