Nuclear War

The single most likely way the world could end is a large-scale nuclear war, most plausibly triggered by escalation between major powers rather than a deliberate plan to destroy civilization. Nuclear weapons remain the only existing technology that can kill billions quickly, collapse global infrastructure, and trigger secondary effects severe enough to threaten human survival worldwide.

Current trends increase this risk: renewed great-power rivalry, active wars near nuclear states, expanding arsenals, weakening arms-control agreements, cyber threats to command-and-control systems, hypersonic delivery systems that shorten decision times, and AI-enabled misinformation or false warnings that could intensify crisis instability. As geopolitical trust declines, the chance of miscalculation rises.

Even if the initial exchange did not kill everyone, the aftermath could. Firestorms in cities could inject soot into the atmosphere, causing abrupt global cooling, crop failures, famine, state collapse, disease, and cascading conflict over remaining resources. That combination makes nuclear war the most probable single pathway to a true global end, compared with slower-moving threats like climate change or more speculative ones like rogue AI or engineered pandemics.