This post is part of a series of rough posts on nuclear risk research ideas. I strongly recommend that, before you read this post, you read the series’ summary & introduction post for context, caveats, and to see the list of other ideas. One caveat that’s especially worth flagging here is that I drafted this in late 2021 and haven’t updated it much since. I’m grateful to Will Aldred for help with this series.

One reason I'm publishing this now is to serve as one menu of research project ideas for upcoming summer research fellowships.

Some tentative bottom-line views about this project idea

What is this idea? Why might this research be useful? How could it be tackled?

Following nuclear conflict, nuclear fallout would likely kill some people directly and also contaminate crops, water, etc. in some areas.

This project should probably focus on investigating how significant these effects would be following various nuclear conflict scenarios, and in particular whether it’s plausible the effects could be large enough to rival those of nuclear winter or to meaningfully increase existential risk. If that does seem plausible, this project could progress to questions such as what can be done to reduce the likelihood of scenarios with such significant fallout effects, what can be done to improve resilience to or recovery from such fallout effects, and how this should update our views on how much to prioritise nuclear risk and what to prioritise within this area.

This could involve considering how the answers to those questions would be affected by plausible technological developments (see Aird & Aldred, 2023), changes in arsenal sizes, or other future changes.

Similar to the case with nuclear EMP attacks, I’d guess that fallout effects would be far less harmful than nuclear winter and that, even conditional on nuclear conflict occurring, they would have less than a 1 in 1000 chance of causing or strongly contributing to an existential catastrophe. I think this makes this research project idea relatively low-priority.

However, I also feel uncertain about those guesses and think that that uncertainty might be substantially reducible with even just 0.5-3 weeks of work, which makes me think this project could be worth pursuing for someone with a strong fit for or interest in it. Also, that risk estimate is based on my tentative belief that it’s very unlikely there’ll be technological developments in the next few decades that massively increase expected harm from fallout conditional on nuclear conflict, but that belief could be misguided.

Ways of tackling this project could include:

• Reading parts of existing work on the topic
• Interviewing several experts on the topic
• Doing some Fermi estimates or more careful modelling, focused in particular on whether we can basically “rule out” this as concern on par with nuclear winter

I’d intended to briefly research this topic myself, so I made some rough notes on it, which can be found here and here.

Some relevant previous work

• Denkenberger and Pearce (2018)
• Ladish’s (2020) section on “Radiation”, and the comments there
• Rodriguez’s (2020) section on “What is the likelihood that radiation causes extinction?”, and the comments there