Nuclear weapons have the potential to kill hundreds of millions of people directly, and billions due to subsequent effects on agriculture. The potential for a ‘nuclear winter’ poses some unknown risk of human extinction, or of a social collapse from which we never recover.

There are many examples of moments in which the US or Russia appear to have come close to accidentally or deliberately using their nuclear weapons, so a nuclear war between global powers might not be as unlikely as it seems.

However, nuclear security is already a major topic of interest for governments, making it harder to have an impact relative to other global problems.

Most opportunities to influence the risk from nuclear weapons seem to be through work in the military or foreign policy institutions, or research in the think tanks that offer them ideas for how to lower the risk of nuclear conflict. Some less conventional approaches could involve working independently to improve relationships between people in the nuclear powers, or trying to improve the resilience of our food supply in the case of a serious agricultural collapse.

Our overall view


Working on this issue seems to be among the best ways of improving the long-term future we know of, but all else equal, we think it’s less pressing than our highest priority areas.


We believe work to reduce the probability of nuclear war has the potential for a large positive impact, as nuclear war would have devastating effects, both directly and also through secondary effects such as nuclear winter. We think the chance of nuclear war per year is around 0.01–2%. Assuming this remains constant, the chance of a nuclear war is 10–85% in the next 100 years, although we expect this yearly chance will decrease over time. Estimates of existential risk from nuclear war within the next 100 years range from 0.005% to 1%. We think the direct existential risk from nuclear war (i.e. not including secondary effects) is less than 0.01%. The indirect existential risk seems around 10 times higher.


This issue is not as neglected as most other issues we prioritise. Current spending is between $1 billion and $10 billion per year (quality-adjusted).1


Making progress on nuclear security seems somewhat tractable. While many routes to progress face significant political controversy, there may also be some more neglected ways to reduce this risk.2

Profile depth


This is one of many profiles we've written to help people find the most pressing problems they can solve with their careers. Learn more about how we compare different problems, see how we try to score them numerically, and see how this problem compares to the others we've considered so far.

Why might nuclear security be an especially pressing global issue?

Despite reductions in nuclear weapons arsenals following the Cold War, there are still around 10,000 nuclear warheads in the world, with the United States and Russia in possession of around 90% of the world’s weapons.

These weapons have the potential to cause suffering and destruction on an unprecedented scale. Research by 80,000 Hours Research Analyst Luisa Rodriguez estimated that a US–Russia nuclear exchange would directly kill 51 million people (90% confidence interval: 30 million–75 million deaths).

Total deaths caused directly by nuclear exchange

Although initial effects from such a nuclear exchange would be horrible, the aftereffects could be even worse. A nuclear exchange could cause a nuclear winter — a release of black carbon into the atmosphere, blocking the Sun’s thermal energy. That in turn would lower temperatures globally for up to a decade, open up new holes in the ozone layer, and reduce global rainfall by about 10% — triggering crop failures and resulting in widespread food shortages. Nonetheless, there remains uncertainty about how many nuclear weapons would have to be detonated for long-lasting climatic effects to be triggered, and whether the effects of a nuclear winter would be merely bad, or an existential risk to humanity.3

Rodriguez estimates that a famine caused by a US–Russia nuclear exchange would kill around 5.5 billion people (90% confidence interval: 2.7 billion–7.5 billion deaths). That is, between 36% and 96% of the world population would die a horrible and prolonged death.

But worse still, nuclear war is thought to create some risk of outright human extinction. Various estimates have been made of this risk:

  • In The Precipice, Toby Ord estimates the chances of existential catastrophe resulting directly from nuclear war by 2120 as 0.1%.4
  • A survey of academics at the Global Catastrophic Risk Conference by the University of Oxford estimated a 1% chance of human extinction from nuclear wars over the 21st century.5
  • Pamlin and Amstrong (2015) estimate a 0.005% chance of “infinite impact” from nuclear war by 2115.6

As with climate change, we think that nuclear war may pose a greater indirect existential risk than risk in itself. That is, we think there are reasons to be particularly concerned about the resilience of a world after the use of nuclear weapons — for example, whether we could be resilient to global catastrophic biological risks or risks from currently unknown future technology. We’d estimate that this indirect risk is around 10 times higher than the direct risk of nuclear war.

The risk of such a catastrophic nuclear exchange is fairly low, because neither side would want such an outcome. That said, there remains some possibility of:

  • Escalation from a traditional conflict unintentionally leading to a nuclear war (e.g. escalation of conflicts in Kashmir, Taiwan, or Ukraine).
  • One nuclear state incorrectly believing that they are being attacked due to a technical error and retaliating.
  • A highly irresponsible leader taking power in a nuclear state, or a breakdown in the nuclear chain of command.

Chatham House has compiled 16 examples of nuclear ‘near misses’ through history that include examples of each of these risks.7 In one notable example of a near miss in 1983, the USSR’s early warning system detected the launch of five missiles by the US. The officer on duty at the early-warning command centre, Stanislav Petrov, correctly guessed that this was a false alarm and decided not to relay the warning up the chain of command.

Overall, estimates of the probability of a nuclear attack each year — deliberate or accidental — range between 0.01% and 2.21%.

What are the major arguments against working on this problem?

This area receives a lot of attention already from governments, the military, think tanks, and international organisations (such as the United Nations). It is almost universally recognised as a risk that needs to be reduced. As a result it is considerably less neglected than other top problems.

The risk is dominated by decisions at the highest levels of foreign policy and the military, which may make it hard for most people to have much influence without dedicating their career to building expertise and credibility.

But we have also seen more novel approaches to reducing the existential risk from nuclear conflict that don’t rely primarily on influencing governments — things like finding ways to produce food without the Sun or building shelters could reduce the existential risks posed by nuclear war.

Because of the nature of nuclear deterrence and conflict between countries, there is the risk of accidentally causing harm. For example, discouraging countries from maintaining an aggressive posture in which they say they will use nuclear weapons if attacked could make the world less safe by encouraging conventional conflict.

Key judgement calls you need to make

  • How would a nuclear war play out? There’s lots of uncertainty about what would really happen during a nuclear war. For example:
  • Likelihood of recovery from collapse. If a nuclear catastrophe led to societal collapse, how likely is it we would be able to recover back to our present state, and beyond? We think this is unclear, though suspect recovery is more likely than not. Luisa Rodriguez has written about this in more detail.
  • Importance of existential risks. This problem has a particularly large scale if you place value on mitigating a disaster that would prevent the existence of all future generations. We think this is indeed very important.
  • Comfort with uncertainty. It is not possible to have strong evidence that interventions to solve this problem will succeed, or even which interventions would be net good or net bad, so you need to be comfortable with a high chance of not having any influence.

What can you do about this problem?

There are a range of possible options for reducing the risk of nuclear conflict, none of which we have yet investigated in great detail:

  • Work on improving foreign relations between the main nuclear powers (the US, UK, France, Russia, and China) and defusing any potential conflict.
  • Convince politicians or voters in these countries to prioritise avoiding war above other concerns.
  • Ensure that monitoring of first strikes and communication between nuclear powers is sufficiently good to prevent a false alarm escalating into a full-scale war.
  • Develop resilience within command and control structures in militaries to reduce the risk of false alarms.
  • Prevent nuclear proliferation.
  • Encourage declarations of no first use policies.
  • Ensure nuclear materials are safely guarded and cannot be used by rogue actors.
  • Prevent the development of ballistic missile defence in the US in hopes of making US–Russia and US–China mutual arms reductions more likely.
  • Reduce the deployment of nuclear weapons that force decisions to be made in short periods of time, like nuclear-armed cruise missiles or intercontinental ballistic missiles.
  • Work on improving foreign relations at other nuclear weapon flashpoints, such as India and Pakistan, North Korea, or Iran and Israel.
  • Shrink nuclear stockpiles.
  • Improve adaptation and recovery in the face of an electromagnetic pulse (EMP) attack.
  • Improve resilience of the food supply to nuclear winter.
  • Build civilisational refuges to increase the chances that at least some people survive the worst kinds of nuclear catastrophe.

Most of these opportunities are only available within the foreign policy, intelligence, and military establishments of nuclear powers.

A few — such as peace activism, increasing cooperation between the nuclear powers, or foreign policy research — can be conducted independently through think tanks and academia.

Open Philanthropy conducted a shallow investigation of nuclear weapons policy, and concluded that “the largest potential gaps in this space appear to be work on nuclear weapons policy outside of the U.S. and U.S.-based advocacy, with the former gap being larger but harder for a U.S.-based philanthropist to fill.”

Another option is to work on this problem indirectly by reducing the risk of great power conflict.

What skills and resources are most needed?

To work in this space, it’s helpful to have:

  • Technical expertise in nuclear weapons policy.
  • Expertise in diplomacy, foreign policy, and minimising the risk of war.
  • Influence over public attitudes.

The above skillsets are also most needed particularly relating to countries where there are existing or potential stockpiles, such as the US, Russia, Pakistan, India, Israel, Iran, and North Korea.

Who is working on this problem?

The area is a significant focus for governments, security agencies, and intergovernmental organisations.

Within the nuclear powers, some fraction of all work dedicated to foreign policy, diplomacy, military, and intelligence is directed at ensuring nuclear war does not occur. While it is hard to know exactly how much, it is likely to be in the billions of dollars or more in each country.

The US budget for nuclear weapons is comfortably in the tens of billions.8 Some significant fraction of this is presumably dedicated to control, safety, and accurate detection of attacks on the US.

In addition to this, some intergovernmental organisations devote substantial funding to nuclear security issues. For example, in 2016, the International Atomic Energy Agency had a budget of €361 million.9 Total philanthropic nuclear risk spending in 2021 was approximately $57–190 million.

Philanthropic organisations working on reducing nuclear risk include:

What can you concretely do to help?

We’ve written a number of career reviews that we think could be particularly effective if you choose to focus on reducing risks of nuclear war:

Other things that might help you enter the field:

Finally, you might also consider donating to the Future of Life Institute, Cambridge Centre for the Study of Existential Risk, Alliance to Feed the Earth in Disasters, or the Global Catastrophic Risks Institute.

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    Notes and references

    1. The resources dedicated to preventing the risk of a nuclear war globally, including both inside and outside all governments, is probably $10 billion per year or higher. However, we are downgrading that to $1–10 billion per year quality-adjusted, because much of this spending is not focused on lowering the risk of use of nuclear weapons in general, but rather protecting just one country, or giving one country an advantage over another. Much is also spent on anti-proliferation measures unrelated to the most harmful scenarios in which hundreds of warheads are used. It is also notable that spending by nongovernment actors represents only a tiny fraction of this, so they may have some better opportunities to act.

    2. Unintended effects make it hard to say which policies will truly reduce the risks.

    3. Luke Oman estimates the probability “for the global human population of zero resulting from the 150 Tg of black carbon scenario in our 2007 paper would be in the range of 1 in 10,000 to 1 in 100,000.” This being said, we think this estimate is too low, as it doesn’t account for the potential for weaknesses in their model or the risk of a societal collapse causing a permanent reduction in humanity’s ability to reach its potential (which is nonetheless an existential risk even if people remain).

      See also Wikipedia’s summary of criticism of the idea of nuclear winter .

    4. The Precipice (2020), Toby Ord. Chapter 6 “The Risk Landscape.”

    5. Archived link

    6. “Infinite impact… refers to the state where civilization collapses and does not recover, or a situation where all human life ends.” From Pamlin and Armstrong (2015), Global Challenges: 12 Risks that Threaten Human Civilisation, Global Challenges Foundation. Archived link

    7. Archived link

      Section 4 of “A Model for the Probability of Nuclear War,” Baum et al., 2018 also lists relevant historical incidents.

    8. Archived link

    9. Archived link