US Dept. Of Energy/SPL

Sabres are rattling again between Moscow and Washington, not to mention India and Pakistan, feuding over Kashmir. China’s nuclear arsenal is growing. Some still fear the nuclear intentions of Iran. North Korea is a nuclear power. The cold war may be over, but the weapons and geopolitical flashpoints are still there. Could nuclear war happen sometime in the next 60 years?

The world still possesses around 10,000 nuclear warheads, overwhelmingly in Russia and the US. But let’s assume these two nations do not press the button, and that tensions eventually explode between India and Pakistan.

Most people away from South Asia might imagine such a conflict would not threaten them too much. Think again. The two countries have just over 200 relatively small nuclear warheads between them. Suppose they unleash half of them, a hundred 15-kilotonne weapons the size of Little Boy, dropped on Hiroshima in 1945.

The carnage from the blast, as well as firestorms and radiation in megacities like Karachi and Delhi, would kill millions. But that would be just the start, according to simulations by Alan Robock of Rutgers University in New Jersey and Michael Mills at the National Center for Atmospheric Research in Boulder, Colorado.

The fires would send about 5 million tonnes of hot black smoke into the stratosphere, where it would spread round the world. This smog would cut solar radiation reaching Earth’s surface by 8 per cent – enough to drop average winter temperatures by a startling 2.5 to 6 °C across North America, Europe and much of Asia, and not just for a few days. It would …