Risks from the UK's planned increase in nuclear warheads

Matt Goodman

Abstract

In March 2021 the UK Government integrated review of Security and Defence announced the intention of the UK government to increase the UK’s nuclear stockpiles from 195 to 260 nuclear warheads. In this post I will argue that this would cause a decrease in nuclear security throughout the world.

Background

In November 2020 the UK government announced its intentions to increase government spending by £16.5 billion over four years. In March 2021 the Integrated review announced details of where this spending would be spent, including an increase of the number of nuclear warheads from an estimated 185, of which 120 are operational, to a cap of 260. The increase scraps a 2010 government plan to “reduce our total stockpile to no more than 180 by the mid 2020s”. The reasons for the reversal are unclear but seems to reflect fears of growing Chinese and Russian military capabilities, with UK secretary of defence specifically mentioning Russian investments in ballistic nuclear missile defence. The increase in both arms funding and nuclear warheads seem to align with the UK prime minister Boris Johnson’s vision for a post-Brexit ‘Global Britain’ to be a major player on the world stage.

Risks

The biggest risk I see is the triggering of a new nuclear arms race. The UK ratified the Nuclear non-Proliferation Treaty (NPT) in 1970. The Treaty requires countries that have nuclear weapons to disarm, and those that don’t have them not to get them. By so flagrantly breaking the terms of the treaty, Britain signals that it is ok for other countries to break the terms, and may risk a new new nuclear arms race and era of international law-breaking. A counter-argument to this claim is that China and Russia have already engaged in a nuclear expansion program - possibly a nuclear arms race has already began, the UK is just responding, and Russian and Chinese nuclear expansion has already rendered the NPT effectively void.
Risk of nuclear launch false alarms does not seem to increase. The UK’s nuclear weapons launch platform is four Vanguard-class submarines. Though the number of warheads is increasing, the number of launch platforms isn’t, so the risks of it wrongly appearing that the UK has launched a nuke probably doesn’t increase.
Risks of accidental detonation, stealing, sabotage, leakage etc may be slightly increased due to having an increased number of warheads.
~~Some research on nuclear winter~~ suggests that 100 Hiroshima- sized nuclear detonations would be enough to destroy the majority of human life on earth.Under such a model, it makes no sense for any country to have more than 100 warheads. Though the increase in warheads is negligible compared to the thousands of warheads owned by Russia and the USA, any increase in the numbers of ready to launch warheads can be seen as taking humanity closer to extinction through nuclear winter.

Possible Actions

Establish a campaign against the UK’s increase in nuclear warheads. The UK is an established democracy and there are plenty of examples where public pressure has caused a U-turn in government policy- far more so than in China or Russia, which are also enlarging their nuclear capabilities. I myself am lack the skills and time to lead such a campaign, and I also have little in-depth knowledge of foreign affairs, political lobbying or nuclear military strategy.However I am a Javascript web developer and I have been part of https://www.point7percent.org/, a campaign against the UK’s cuts to foreign aid, and I could potentially re-work the website to work for an anti-proliferation campaign.

Some useful first actions for a campaign could be:

Researching UK public opinion on nuclear weapons.
Researching the history of the UK anti-nuclear movement. Establish a base rate for how often anti-nuclear campaigns have achieved their stated aims, and what worked in the past.
Collating a list of UK anti-nuclear pressure groups, and getting their opinion on such a political campaign.

Useful links

UK government docs

https://www.gov.uk/government/publications/global-britain-in-a-competitive-age-the-integrated-review-of-security-defence-development-and-foreign-policy

https://www.gov.uk/government/news/pm-to-announce-largest-military-investment-in-30-years#:~:text=The%20Government%20has%20already%20pledged,compared%20to%20last%20year's%20budget.

UK government docs (past policy)

https://www.gov.uk/government/news/reduction-in-uk-nuclear-warheads-begins

Interview with UK Defence Secretary (Mentions warheads 0.755)

https://www.bbc.co.uk/programmes/p09bd7gf

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LarksAug 16 202125

Some research on nuclear winter suggests that 100 Hiroshima- sized nuclear detonations would be enough to destroy the majority of human life on earth.Under such a model, it makes no sense for any country to have more than 100 warheads.

I don't see how you can draw such a conclusion. This report concluded that 100 nukes attacking 100 different cities would cause dramatic climate change, but it could still make sense to have more warheads, as you might have other use cases for them. For example, destroying hardened military targets could take multiple warheads but produce much less smoke than a single city. Additionally, some fraction of your warheads could be destroyed prior to use, increasing the ex ante number required for deterrence.

Matt GoodmanAug 17 20212

Thanks for your comment, it has forced my to clarify in my mind a few things, specifically the distinction between 100 nuclear weapons, and the smoke from 100 destroyed cities - in this manner I misinterpreted the report I was quoting.

In this 80 000 hours interview, Daniel Ellsberg talks about 100 warheads being an upper bound for how many nuclear weapons a country needs to provide an effective nuclear deterrent. Quoting:

"As Herbert York put it... how many weapons does it take to deter an enemy that is capable of being deterred from a nuclear attack? And he said one or 10, or if you really stretch, a hundred. He got to that by saying 100 weapons give you the capability of one individual to destroy as many people as died in World War 2, 60 million in a day or two. It shouldn’t have more than that.
So he said the number you need for this purpose then is between one to 10 to 100, and closer to one than 100."

If he's correct, the UK doesn't need any more nuclear weapons than it already has to provide an effective deterrent, and it could have less weapons, and still have an effective deterrent.

some fraction of your warheads could be destroyed prior to use, increasing the ex ante number required for deterrence.

I don't think this is true for the UK's nuclear deterrence strategy. The UK's nuclear warheads are launched only from four Vanguard-class submarines. Each one carries 8 (but can carry up to 16) Trident nuclear missiles, and at least one is on active service at any one time. This last part is crucial- the deterrence strategy relies on the location of the active submarine and its' warheads being very hard to detect, and I would argue the number of warheads beyond a certain point is irrelevant to deterrence.

All this is to say that that I don't think the argument that 'we need more nukes to have a valid deterrent' is valid, and I think we can have a valid deterrent with less nukes that we currently have. Even if I did believe that increasing the UK's number of nukes increased our deterrent, I would think that the additional danger this could cause by triggering a new arms race, would be more dangerous for the UK and the world.

I must admit I feel a profound disgust reflex to the idea that any one country theoretically has the power to destroy almost all human life on earth, and I strongly dislike the idea of my country being able to do so. I do not trust our leaders, or any other world leader, to have that power.

MichaelA🔸Aug 28 20212

To add to what Larks said, I would also say that:

it's not the case that "Some research on nuclear winter suggests that 100 Hiroshima- sized nuclear detonations would be enough to destroy the majority of human life on earth"
even the smaller claim that that research does make is contested and some parts of it are based on pretty shoddy methods (especially the reasoning to go from reduced crop yields to famine death)
"the majority of human life on earth" would in any case be less than "almost all human life on earth", and the distinction might matter a lot from an existential risk perspective (since recovery looks much less likely if we have 0.01% of people left than if we have 1%, and much less likely with 1% than with 40%)

To expand on that:

I don't remember what the specific paper you cite claims about how many deaths would occur, and I can't quickly find it from skimming, but more recent work by the same authors tends to make the claim that there might be ~2 billion deaths. That is a hell of a lot, but also "only" 25% of the world's population.
And that number is based in part on this non-peer-reviewed report by an advocacy organisation, the methodology in which is very shoddy. (One key issue, from memory, is that it basically argues for "2 billion people could be food insecure", and then later implies that it had argued for "2 billion people could die of famine", despite the fact that there's a big difference between those two things.)
And other authors question other parts of the models leading to that estimate.

(I have more detailed notes on all of this, which I could share on request, but they're not polished.)

MichaelA🔸Aug 28 20212

Btw, here's a relevant section of a post I'm drafting on "10 mistakes to avoid when thinking about nuclear risk", which overviews what I see as some key points on nuclear winter etc.. (I could probably share the draft with you if you want.)

Mistake 5 & 6: Ignoring the possibility of major climate and famine effects following nuclear conflict—or overstating the likelihood/severity of those effects

When thinking about nuclear risk, people often focus on the immediate harms (e.g., from the blast) and the harms from radioactive fallout. And those harms could indeed be huge! But those harms could be dwarfed by the harms from major cooling of the climate - perhaps a nuclear winter, or perhaps a smaller version of the same effects. That cooling could perhaps cause huge numbers of famine deaths (plausibly in the billions, for some nuclear conflicts). And this seems the most likely way for nuclear war to cause an existential catastrophe.[1]

...or maybe not! The effects depend on factors such as:

how many detonations occur
how much flammable material is in the targeted areas
how much black carbon fires in these areas would produce and would reach high enough in the atmosphere to persist there for years
how severely agricultural production would be reduced by various potential climate effects
how people would respond to expected or occurring agricultural production issues (e.g., how well could they adjust what crops they grow, where, and how; how much would food usage patterns change; would international trade continue)
how likely civilization is to recover from a collapse

And, unfortunately, each of those questions are contested, complex, and under-researched.

Ultimately, I suggest:

Recognising that major climate and famine effects are plausible, but that whether they’ll happen and how bad they’ll be is quite uncertain.
Seeing that as a key consideration when deciding (a) how much to prioritise nuclear risk relative to other problems and (b) which nuclear conflict scenario to prioritise reducing the odds of.

Considering interventions to reduce how bad the climate or famine effects would be (e.g., [[example]])

[1] I still consider myself quite confused on those topics, but here are some of my current bottom-line beliefs, in brief:

Climate effects severe enough to qualify as “nuclear winter” seem likely in scenarios in which there are thousands of nuclear detonations on high-population-density areas (e.g., cities or towns). In contrast, nuclear winter seems unlikely in scenarios with less than a hundred detonations on high-population-density areas. I really wish I had a clearer sense of the probabilities, especially for various scenarios between those extremes. (See, e.g., Toon et al., 2007; Reisner et al., 2018; Robock et al., 2019.)
If nuclear winter occurred, it would probably cause at least hundreds of millions of deaths. It’s also plausible but unlikely that it’d lead to an existential catastrophe (via the resulting famine combined with other effects, e.g., further conflict triggered by the famine). (See, e.g., Aird, 2020; Beckstead, 2015; Ladish, 2020; Ord, 2020; Rodriguez, 2019; Rodriguez, 2020.)
Climate effects that are similar to but smaller than “nuclear winter” could plausibly cause hundreds of millions or perhaps billions of deaths. But such effects would be much less likely to cause existential catastrophe.
Even a low probability of existential catastrophe is still really terrible and can be well-worth reducing further!

Matt GoodmanSep 29 20211

Just coming back to this- thanks for these comments! In light of your and Lark's comments I'd no longer endorse this section: "Some research on nuclear winter...". I'll be very interested to hear your coming

However I'm still very concerned by the precedent this sets for nuclear non-proliferation. This move seems a pretty clear breach of the non-proliferation treaty , and the risks it created of a new nuclear arms race remains the central thing that I'm worried about.

Perhaps more relevant to that since this was published is the new of the new AUKUS security pact. I'm really glad to see that being discussed on the EA Forum here.

MichaelA🔸Sep 30 20212

(Btw, on non-proliferation and arms racing, there are some relevant forecasts as part of the Nuclear Risk Forecasting Tournament I'm putting together with Metaculus, and there will be more put up next week and then again over the coming months. I'll also write up some summaries later.)

MichaelA🔸Aug 28 20212

I don't think this is true for the UK's nuclear deterrence strategy. The UK's nuclear warheads are launched only from four Vanguard-class submarines. Each one carries 8 (but can carry up to 16) Trident nuclear missiles, and at least one is on active service at any one time. This last part is crucial- the deterrence strategy relies on the location of the active submarine and its' warheads being very hard to detect, and I would argue the number of warheads beyond a certain point is irrelevant to deterrence.

If that's roughly the case (which I haven't looked into), then it seems like the UK's "secure second strike" capability is actually ~1/4 of its total number of warheads. In which case an increase to 260 is increasing to a secure second strike capability of 65, i.e. still less than 100.

On the other hand, that Ellsberg quote seems to be simply saying that 100 should be the upper limit, rather than specifying "100 that would likely survive a nuclear first strike against that state". But that mostly just makes me think that that quote shouldn't be given much weight. Other things that make me think that are that:

he's just one person
this is just a podcast interview so may lack some of the nuance of his full views
I think some of his claims in that interview and his book are over-the-top or misleading (though I also found parts of that interview and his book useful)
- (I could see if I have notes that would allow me to elaborate, if you'd like)

Btw, I'm drafting a post on "What would be the ideal size and composition of nuclear arsenals?", which I hope to post to the Forum ~October (I'm working on various other things in parallel). I definitely won't have definitive answers, and it'll probably mostly just shallowly highlight various considerations and minor arguments, but may still be of interest to you and to readers of this post.

MichaelA🔸Aug 28 20214

Thanks for this post! Though I disagree with some key claims in it (as noted in my other comments), I also thought it was a handy, concise summary of some important events and possible implications. And your suggested possible actions sound to me like they'd probably be useful. (Though I'm more agnostic about how high-priority they'd be, relative to other ways of reducing nuclear risk.)

Also, more generally, it seems to me that reducing odds of increases of numbers of warheads in countries that already have some is a relatively neglected possible goal for nuclear risk reduction. (This is a relatively tentative view, since that definitely does get some discussion, e.g. in the context of US-Russia arms control treaties. But it seems like the focus is usually on arms reductions, preventing proliferation, or reducing the odds of war.) So I appreciate this post highlighting that.

Risks from the UK's planned increase in nuclear warheads

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Abstract

Background

Risks

Possible Actions

Useful links

UK government docs

UK government docs (past policy)

Interview with UK Defence Secretary (Mentions warheads 0.755)

UK nuclear weapons overview

Legal opinion on the legality of the UK’s actions

Media coverage of the UK’s weapons increase

Coverage from anti-nuclear groups

UN docs on the Nuclear non Proliferation treaty

Nuclear winter research

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Mistake 5 & 6: Ignoring the possibility of major climate and famine effects following nuclear conflict—or overstating the likelihood/severity of those effects