Nuclear War

Escalating great-power rivalries, the erosion of arms-control treaties, and the integration of artificial intelligence into early-warning and command systems are shrinking the margin for error. A miscalculation, cyberattack, or regional conflict drawing in nuclear-armed states could trigger a large-scale exchange. The resulting nuclear winter—caused by firestorms injecting soot into the stratosphere—would collapse global agriculture, leading to mass starvation and the breakdown of civilization within a few years.