Technological University and Tennessee State University analysed how many missiles a country could fire before unleashing a chain of events so catastrophic that scores of its own citizens would die even without retaliation. Using estimates of soot and dust thrown into the air by nuclear blasts, and the consequent blotting of the Sun, the team concluded that if a nation were to detonate fewer
than 100 warheads, the consequences, though dire, would mostly be confined to other regions. Above 100, however, and the “environmental blowback” of a oneway strike would wreak global havoc,
reducing agricultural output by up to 20% and causing widespread food shortages. Most of the world’s nine official nuclear nations have more than 100 warheads: Britain has 215, France has 300, and America and Russia have around 7,000 each. “With 100 nuclear weapons, you still get nuclear deterrence, but avoid the probable blowback from a nuclear autumn that kills your own people,” said Professor Joshua Pearce, one of the report’s authors.
