The Russian invasion of Ukraine has made us all more acutely aware of the dangers of nuclear conflict than at any time since the end of the Cold War. Now, with Russia losing ground against an entrenched Ukrainian resistance, the stakes are only going to get higher.

Avril Haines, the director of National Intelligence for the Biden administration, recently stated that Russian President Vladimir Putin “would probably only authorize the use of nuclear weapons if he perceived an existential threat.” But, as the war drags on, Haines added that it heightens the potential for Putin to see the prospect of defeat as an existential threat.

Any potential of something as devastating as nuclear war should be cause enough for alarm.

Even a singular nuclear launch and limited response from NATO or elsewhere could, in a nightmarish but possible scenario, cascade into a full-scale nuclear exchange. Though it is extremely difficult to accurately predict the likelihood of this happening, it is undeniable that many are justifiably concerned. According to a March 2022 poll, 69% of U.S. adults said that they were worried that Putin’s invasion of Ukraine would lead to nuclear war.

We are all familiar with the immediate devastation that nuclear weapons could do to the cities they target and the radiation clouds that would spread further afield. Nuclear detonations also cause fierce firestorms that loft soot into the stratosphere, which, in high enough volumes, can block out the sun and reduce global temperatures and rainfall. This soot cloud would persist for several years, triggering a phenomenon known as nuclear winter.

A 2007 study suggests global nuclear winter effects could be triggered by as few as 100 low-yield nuclear weapons. If a larger proportion of the world’s 12,700 nuclear bombs were used, the effects would be devastating.


Depending on the severity of the winter, crop yields in the United States could drop to 2% of their current output for up to a decade. This would result in starvation for the majority of Americans, while leaving those left to face subzero temperatures in summer and cascade effects that would almost certainly be fatal.

I began my career in international relations a few years after 1983 — when a war game brought the world close to the brink of a nuclear launch — in order to help prevent nuclear weapons from spreading and to advocate for disarmament. I am now a researcher at Cambridge University’s Center for the Study of Existential Risk, where we look at the different ways that we could trigger an end to our civilization and how they can be counteracted.

It feels as if there is little we can do about the nuclear threat prompted by the invasion of Ukraine, but that’s not true. We need to push our elected representatives to avoid triggering any serious escalation.

Ukraine deserves our support, and Russia our condemnation. But we also have to consider how Russia is perceiving the war and to what extent it would view defeat as an existential threat. In order to prevent the worst outcomes, we need to draw the Russians into negotiation and be prepared to compromise.

Our governments have displayed a singular lack of leadership, commitment and imagination when it comes to finding diplomatic solutions. This needs to change. And urgently.