Mini advent calendar of Xrisks: nuclear war

Stuart_Armstrong

The FHI's mini advent calendar: counting down through the big five existential risks. The first one is an old favourite, forgotten but not gone: nuclear war.

Nuclear War
Current understanding: medium-high
Most worrying aspect: the missiles and bombs are already out there
It was a great fear during the fifties and sixties; but the weapons that could destroy our species lie dormant, not destroyed.

There has been some recent progress: the sizes of the arsenals have been diminishing, fissile material is more under control than it used to be, and there is more geo-political peace and cooperation.

But nuclear weapons still remain the easiest method for our species to destroy itself. Recent modelling have confirmed the old idea of nuclear winter: soot rising from burning human cities destroyed by nuclear weapons could envelop the world in a dark cloud, disrupting agriculture and the food supplies, and causing mass starvation and death far beyond the areas directly hit. And a creeping proliferation has spread these weapons to smaller states in unstable areas of the world, increasing the probability that nuclear weapons could get used, leading to potential escalation. The risks are not new, and several times (the Cuban missile crisis, the Petrov incident) our species has been saved from annihilation by the slimmest of margins. And yet the risk seems to have slipped off the radar for many governments: emergency food and fuel reserves are diminishing, and we have few “refuges” designed to ensure that the human species could endure a major nuclear conflict.

There are particulate events in the climate record that a model of nuclear winter could be calibrated against -- any major volcanic eruption, for example. Some have even approached the level of severity predicted for a mild nuclear winter: the "Year Without A Summer" following the 1815 Tambora eruption is the first one I can think of.

This isn't perfect: volcanoes mainly release fine rock ash instead of the wood and hydrocarbon soot that we'd expect from burning cities, which behaves differently in the atmosphere, and while we can get some idea of the difference from looking at events like large-scale forest fires there are limits on how far we can extrapolate. But we should have enough to at least put some bounds on what we could expect.