This is an extract from our report “Nuclear Weapons, the Climate and Our Environment”.
Studies have shown that a nuclear exchange using less than 1% of the world’s 13,400 nuclear weapons would alter the Earth’s climate and precipitate widespread famine.
If 100 Hiroshima-sized nuclear bombs were targeted on cities in a regional nuclear conflict, such as a war between India and Pakistan, firestorms would send millions of tonnes of smoke and dust into the atmosphere. Some of this smoke would be lofted into the stratosphere where it would remain for years, preventing sunlight from reaching the Earth’s surface.
Global average temperatures would drop by several degrees and rainfall would be reduced, impacting food production in many regions for at least a decade. Food scarcity and the resulting increase in food prices would leave two billion people at risk of starvation. Many more would be threatened by epidemics of infectious disease.
This so-called “limited” nuclear war would also damage the Earth’s ozone layer, increasing levels of UV radiation that would harm plants, animals and aquatic ecosystems and pose grave health risks to people, such as vision impairment and skin cancers.
According to Scientists for Global Responsibility, detonation of the 40 nuclear warheads carried on a British nuclear-armed submarine could have similar climactic consequences.
A larger nuclear conflict, such as a war using Russian and US strategic nuclear weapons, would cause a full-blown nuclear winter. The amount of smoke in the stratosphere would block 90% of sunlight across most of the world and global average temperatures would plummet to levels last experienced during the Ice Age, 18,000 years ago.
These climactic changes would “basically kill all of our crops and most of us would be sentenced to death by famine”, according to distinguished climatologist, Professor Alan Robock.
 I Helfand, “Nuclear Famine: A Billion People at Risk? Global Impacts of Limited Nuclear War on Agriculture, Food Supplies, and Human Nutrition” (2nd edn, Physicians for Social Responsibility, November 2013): https://www.psr.org/wp-content/uploads/2018/04/two-billion-at-risk.pdf.
 MJ Mills et al, “Massive global ozone loss predicted following regional nuclear conflict”, PNAS 8 April 2008 105 (14) 5307-5312; https://doi.org/10.1073/pnas.0710058105.
 S Parkinson, “The environmental impacts of the UK military sector” (Scientists for Global Responsibility, May 2020), pp 26 ff: https://www.sgr.org.uk/publications/environmental-impacts-uk-military-sector.
 A Robock et al, “Nuclear winter revisited with a modern climate model and current nuclear arsenals: Still catastrophic consequences”, Journal of Geophysical Research, Vol. 112, D13107, 6 July 2007: https://doi.org/10.1029/2006JD008235.
 A Robock speaking during “Nuclear Weapons 101 – risks, consequences and solutions”, a panel discussion at the ICAN Paris Forum (14 February 2020): https://www.facebook.com/icanw.org/videos/143425496747324/.