With the Russian invasion of Ukraine, the risk of nuclear war has markedly increased. But, as Dr Philip Webber, SGR, points out, the threat comes from all nuclear weapons, not just those in Russian hands.
Responsible Science blog, 3 March 2022
The repeated euphemistic phraseology of ‘nuclear deterrence’, or of a ‘nuclear umbrella’, has lulled most people into a false sense of safety and security.
Reacting to Western support for Ukraine as Russian forces invaded, President Putin announced an increase in the alert level of their nuclear weapons.  Many commentators expressed shock, assuming that ‘the world had moved on’ from such threats. But they forgot – or did not know – that there are already over 900 Russian, and an equivalent number of US, long-range warheads kept ready to fire at a few minutes’ notice.  This has been the situation since the end of the Cold War, three decades ago. It is a highly risky situation that has been criticised even by many senior military and political figures.  Indeed, UK and French nuclear weapons can also be made ready to fire with some 15 minutes’ notice in a crisis. 
The reality is that ‘nuclear deterrence’ threatens death and destruction on such an extreme scale that it is hard to imagine. This is no accident – a detonation above a city is chosen to maximise the lethal blast and fire radius.
SGR has extensively documented the risks, impacts and dangers of the deployment and use of nuclear weapons using the latest data from scientific studies. 
For example, the use of just one typical nuclear weapon  airburst over a major city would overwhelm any possible medical capacity with injuries including severe burns and radiation sickness.  In this scenario, the casualty count could quickly climb to more than a million people. A larger weapon – such as routinely deployed by Russia or the USA – could kill and injure considerably more. 
Indeed, the use of no more than 100 nuclear weapons would be completely disastrous for all humanity in terms of death, injury, radiation releases and widespread ecosystem impacts. Nuclear fireballs would create huge ‘firestorms’, injecting smoke high into the atmosphere sharply reducing sunlight and creating a ten-year ‘nuclear winter’. This would bring about mass starvation and societal collapse as crops failed in unseasonal frosts and darkness. 
In 1985, the leaders of the USA and the Soviet Union agreed that “a nuclear war cannot be won and must never be fought”.  This was affirmed by the leaders of the five largest nuclear weapons nations – Russia, the USA, China, France and the UK – as recently as January this year.  They are right. All the detailed military simulations of nuclear conflict come to the same conclusion – no one can ‘win’. All sides, bystanders and the global environment would be destroyed.
But the clear implication is ignored – that nuclear weapons are rationally unusable. Any use of a nuclear weapon would be disastrous in humanitarian and political terms and would quickly escalate, ending human civilisation. Having large numbers of unusable weapons makes no sense, but this is the policy pursued by the nuclear weapons nations who are all developing new nuclear weapons. Some states – such as the UK – are even increasing their warhead numbers. 
Putin seems to regard his latest nuclear threat as ensuring that he can conduct attacks using conventional weapons without direct retaliation from NATO, under his ‘nuclear umbrella’. This is an example of how nuclear deterrence can be used to facilitate conflict, leading to murderous acts and a humanitarian crisis.
With the war evolving in Ukraine, and as casualties mount, it is again time for organisations such as SGR and the wider peace and environmental movements to make it clear that any possession of nuclear weapons – and acceptance of ‘nuclear deterrence’ – is dangerous and irresponsible. There is no such thing as ‘limited’ nuclear weapons use, it would only lead to global catastrophe. We must take urgent action to publicise the genocidal, ecocidal, and suicidal risk posed by nuclear weapons before they are used by accident, due to equipment failure, or by an unbalanced political leader in a time of extreme tension. We must make the case that the nuclear weapons states should join the UN Treaty for the Prohibition of Nuclear Weapons because it sets out a clear framework to negotiate and verifiably reduce numbers of nuclear weapons to zero.  This would bring about the ultimate goal first set out in the 1968 Nuclear Non-proliferation Treaty – the elimination of all nuclear weapons.
Dr Philip Webber is Chair of SGR, and has written on the threat from nuclear weapons for 40 years, including London After the Bomb (1982) and Nuclear Weapons: a beginner’s guide to the threats (2021).
 See, for example: Global Zero (2015). https://www.globalzero.org/wp-content/uploads/2018/09/global_zero_commission_on_nuclear_risk_reduction_report_0.pdf
 UK Parliament (2006). https://publications.parliament.uk/pa/cm200506/cmselect/cmdfence/986/6031402.htm
 SGR (2022). https://www.sgr.org.uk/projects/nuclear-weapons-threat-main-outputs ; SGR (2021) – as note 2.
 I refer here to a weapon with an explosive power or ‘yield’ equivalent to about 100 kilotonnes of TNT. Many warheads are much larger.
 SGR (2021) – as note 2.
 A nuclear winter would follow the use of 100 ‘small’ (about 15 kilotonne) detonations. SGR (2021) – as note 2.
 Ronald Reagan Presidential Library (1985). https://www.reaganlibrary.gov/archives/speech/joint-soviet-united-states-statement-summit-meeting-geneva
 Federation of American Scientists (2022). https://fas.org/issues/nuclear-weapons/status-world-nuclear-forces/