Nations with huge nuclear arsenals are wasting their money because just 100 missiles would be enough to destabilise the globe and kill their own citizens, scientists have said.
Britain currently possesses approximately 215 warheads of around 15,000 worldwide, the vast majority of which are American or Russian.
But researchers have determined that no nation could fire more than 100 without causing a chain of events so catastrophic the impacts are felt at home.
In the first such exercise of its kind, scientists analysed the “environmental blow-back” of a one-way but massive nuclear strike.
Based on models including those of burnable materials in cities, they calculated the amount of soot and dust that would be thrown into the air by the blasts, the consequent blotting of the sun and damage to the atmosphere.
They found that the “nuclear autumn” of such destruction would damage agricultural output by up to 20 per cent, enough to affect widespread food shortages even on the other side of the world.
The concept of nuclear deterrence has traditionally included the doctrine that the bigger the arsenal, the less likely an adversary is to attack.
However, the authors at Michigan Technological University and Tennessee State University say there is no “pragmatic” reason for any nation to maintain more than 100.
Published in the journal Safety, the study follows the historic Singapore summit between President Trump and Kim Jong Un, where both leaders pledged the “complete denucliarisation” of the Korean peninsula.
There are nine official nuclear weaponised nations: the U.S., Russia, the UK, France, China, India, Pakistan, Israel and North Korea.
Britain’s nuclear deterrent consists of at least one of four nuclear-armed submarines being at sea and ready to launch at any time.
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Although both the Conservative and Labour Parties are officially committed to renewing Trident, Jeremy Corbyn has expressed a preference to scrap it.
Under the disarmament proposed in the the new study, the total number of warheads globally would drop to 900 or fewer.
Professor Joshua Pearce, one of the authors, said: “With 100 nuclear weapons, you still get nuclear deterrence, but avoid the probable blowback from nuclear autumn that kills your own people."
"No country should have more nuclear weapons than the number necessary for unacceptable levels of environmental blow-back on the nuclear power's own country if they were used."
Professor Pearce said modeling showed that if the US were to fire 1,000 nuclear warheads, 50-times more Americans would die than did on 9/11, even if no missiles were fired back.
His team analysed a hypothetical US attack on China using 7,000 weapons, 1,000 or 100.
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Even in the smallest attack, 30 million people would be likely to die form the initial blasts.
The altered atmosphere would be expected to result in an overall drop in global temperature, a 19 per cent reduction in rainfall as well as an increase in ultraviolet radiation.
The study warns that its estimated long-term casualties suffered by the aggressor nation are likely to be a significant underestimate, because they reflect only the predicted deaths directly resulting from food shortage, but not the violence and unrest that such deprivation would cause.