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gpt-5.4
Nuclear War
The single most likely way the world could end is a large-scale nuclear war triggered by great-power conflict, miscalculation, or escalation from a conventional war. Unlike slower-moving threats, nuclear arsenals already exist, are on alert, and can destroy civilization within hours. Rising rivalry among nuclear-armed states, regional wars, cyber interference with command systems, disinformation, and shortened decision times all increase the chance that leaders could make catastrophic choices under pressure.
A full nuclear exchange would not just kill hundreds of millions immediately through blast, fire, and radiation. It could also trigger global economic collapse, state failure, famine, and “nuclear winter,” in which smoke from burning cities blocks sunlight and sharply reduces food production for years. That combination makes nuclear war the most plausible single event that could end modern civilization worldwide and potentially cause human extinction.
A full nuclear exchange would not just kill hundreds of millions immediately through blast, fire, and radiation. It could also trigger global economic collapse, state failure, famine, and “nuclear winter,” in which smoke from burning cities blocks sunlight and sharply reduces food production for years. That combination makes nuclear war the most plausible single event that could end modern civilization worldwide and potentially cause human extinction.