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gpt-5.4

Nuclear War

The single most likely way the world could end is a large-scale nuclear war, most plausibly 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 kill billions directly and indirectly within months.

Current trends make this risk unusually persistent: worsening rivalry among nuclear-armed states, erosion of arms-control agreements, cyber threats to command-and-warning systems, faster weapons that compress decision time, and the possibility that AI-enabled surveillance or decision support could increase false confidence during a crisis. Human error, technical malfunction, or a mistaken interpretation of an attack could be enough.

Even a “limited” exchange could cause global famine through nuclear winter, collapsing food systems and governments far from the battlefield. A full-scale exchange between major powers could destroy modern civilization and plausibly drive humanity to extinction through immediate devastation, radiation, infrastructure failure, disease, and years of climatic shock.