Nuclear weapons: beginner's guide

The document outlines the existential risk posed by the approximately 12,000 nuclear warheads held by nine nations. It explains the physics of fission and fusion weapons and analyzes the catastrophic effects of detonations, ranging from immediate blast and radiation deaths in urban centers to global climate disruption. The guide highlights the instability of 'launch on warning' postures and the potential for 'nuclear winter' and ozone depletion, arguing that even regional conflicts would cause global famine and societal collapse.

• There are approximately 12,000 nuclear warheads globally, with nearly 4,000 deployed and ready to fire. About 90% of these are held by the USA and Russia.
• The USA and Russia maintain a 'launch on warning' status with 300 to 400 missiles each ready to fire within minutes, leaving leaders as little as five to ten minutes to decide on a launch, which increases the risk of accidental nuclear war due to human or technological error.
• Modern nuclear weapons possess immense destructive power; for example, a single Russian SS-18 missile can carry ten 800kT warheads, totaling 8MT, which is more than twice the explosive power of all bombs dropped during World War II.
• A single 100kT warhead detonated over a medium-sized city like Manchester is estimated to cause approximately 80,000 immediate deaths and 210,000 injuries, overwhelming all possible medical and humanitarian responses.
• Even a regional conflict, such as one between India and Pakistan using 100 Hiroshima-sized weapons, could cause 21 million deaths and trigger global climate disruption, including severe frosts, drought, and famine lasting up to ten years in the northern hemisphere.
• Large-scale nuclear war would likely result in the loss of 50% of the ozone layer's protective value due to nitrogen oxide gas and soot, increasing UV radiation and damaging phytoplankton, which are critical to aquatic ecosystems.
• The 2017 United Nations Treaty on the Prohibition of Nuclear Weapons renders the development, production, use, and threat of use of nuclear weapons illegal under international law.

APA

Webber, P. (2025). Nuclear weapons: beginner's guide. Scientists for Global Responsibility. https://www.sgr.org.uk/resources/nuclear-weapons-beginner-s-guide-threats

Chicago

Webber, Philip. Nuclear weapons: beginner's guide. Scientists for Global Responsibility, 2025. https://www.sgr.org.uk/resources/nuclear-weapons-beginner-s-guide-threats.

Wikipedia

{{cite report |last1=Webber |first1=Philip |title=Nuclear weapons: beginner's guide |publisher=Scientists for Global Responsibility |date=4 August 2025 |url=https://www.sgr.org.uk/resources/nuclear-weapons-beginner-s-guide-threats |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{webber2025nuclear, author = {Webber, Philip}, title = {{Nuclear weapons: beginner's guide}}, institution = {Scientists for Global Responsibility}, year = {2025}, month = aug, url = {https://www.sgr.org.uk/resources/nuclear-weapons-beginner-s-guide-threats}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }