Scientists welcome key milestone for nuclear weapons ban treaty

Media release, 25 October 2020

Scientists for Global Responsibility (SGR) welcomes the 50th ratification of the UN Treaty on the Prohibition of Nuclear Weapons – reached late yesterday – which means the treaty will now enter in force on 22 January 2021.

The treaty bans the production, testing, possession and use of nuclear weapons by signatory nations, along with other activities that could enable or assist any other nation to acquire or use these weapons of mass destruction. The treaty now puts nuclear weapons in the same category as other weapons of mass destruction – i.e. biological and chemical weapons – which are banned by international treaty.

The treaty is the culmination of the efforts by campaigners led by ICAN (the International Campaign to Abolish Nuclear Weapons) – 2017 recipient of the Nobel Peace Prize – of which SGR is a partner organisation.

Dr Philip Webber, Chair of SGR, said, "Since SGR's forerunner Scientists Against Nuclear Arms was formed in 1981, we have argued that nuclear weapons pose an unacceptable threat to human civilisation and indeed all life on Earth. There are still currently 1,800 nuclear weapons deployed and ready to fire at short notice – and some of these deployed by the UK. We strongly urge the UK government and other nuclear nations to support this treaty."

Dr Rebecca Johnson, peace activist and first president of ICAN, said "The treaty exists now because of 75 years of humanitarian activism, from the 'Hibakusha' and indigenous survivors of nuclear weapons and testing, to the Aldermaston marchers and Greenham Common peace women who helped to ban nuclear testing and get US cruise missiles removed from British soil. Together we persuaded UN governments to bring this ground-breaking nuclear disarmament treaty into international humanitarian law."


1. The Treaty on the Prohibition of Nuclear Weapons was agreed by the UN in 2017. Honduras became the 50th nation to ratify on 24th October. For more details on the treaty and the wider campaign, see:

2. Scientists for Global Responsibility (SGR) is a UK membership organisation promoting responsible science and technology. Its 700 members include natural scientists, social scientists, engineers and others with expertise in peace and environmental issues. SGR has been a partner organisation of ICAN from soon after it was formed. For more information, see:

3. Dr Philip Webber, a physicist by training, has written and campaigned about the threat from nuclear weapons for 40 years. He is an author of the 1982 book, London After the Bomb, as well as numerous SGR briefings and articles on the issue, including some used by ICAN in a range of international meetings in Norway, Mexico and Austria in the run up to the agreement of the treaty. For a list of SGR’s key outputs on nuclear weapons, see:

4. For more details on the current numbers of nuclear weapons, see: Federation of American Scientists (2020). Status of World Nuclear Forces.

Nuclear explosion

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