Error

This post represents the culmination of research into the severity of the risks of nuclear war. I think the series as a whole was very helpful in figuring out how much the EA movement should prioritize nuclear risk and whether nuclear risk represented a true existential risk. Moreover, I think this post in particular was a great example of how there can be initial errors in analysis and how these errors can be thoughtfully corrected.

Disclaimer: I am co-CEO at Rethink Priorities and supervised some of this work, but I am writing this review in a personal capacity as a personal reflection. I did not share this review with anyone at RP, so it’s quite possible other people might disagree and I may be wrong here, so do not take this as an official RP position.

Thank you for updating your research. I understand that only a handful of scientists are working on the nuclear winter problem. It seems like this is an area where effective altruism and yourself can make a major difference. I do have a few questions about nuclear winter since you mentioned looking into that subject in greater detail for future publications.

1. If cities burn without creating a firestorm to lift black carbon into the stratosphere then would a nuclear winter persist for years or would it quickly rain out?

2. Smoke is the result of incomplete combustion. A firestorm generates enormous temperatures due to the blast furnace effect heating fuels to temperatures between 1,400F and 2,000F. Carbon, like in diamonds, burns at 1,292F to create CO2. A smokeless incinerator is able to burn plastics without releasing black smoke and only release CO2 and water vapor. Do the sources you reference already account for the combustion of pure black carbon in a high temperature firestorm?

3. A few pyrocumulonimbus clouds have been studied. They appear to be mostly water vapor. If a firestorm releases a large amount of water vapor that condenses into ice as it rises then would the black carbon act as condensation nuclei? Would an ice coating change the color and stop the self-heating and rising necessary to reach the stratosphere? If an ice coated black carbon particle does reach the stratosphere then how does that impact the longevity of a nuclear winter?

4. If the sources are ambiguous then is this something that smaller scale table top experiments or additional observations can factually determine?