Nuclear War

Among the existential threats facing humanity, nuclear conflict stands out as the most probable cause of civilizational collapse or human extinction in the near to medium term. As of 2026, the global geopolitical landscape has deteriorated significantly: the Russia-Ukraine war remains unresolved, US-China tensions over Taiwan continue to escalate, and nuclear arsenals are being modernized and expanded by multiple states. Unlike climate change—which is devastating but operates on a slower, degrading timeline—nuclear war can trigger catastrophic, near-instantaneous consequences. A full-scale exchange between major powers would produce immediate deaths in the hundreds of millions, followed by nuclear winter, global famine, and the collapse of supply chains, potentially rendering large portions of the planet uninhabitable.

The risk is compounded by the erosion of arms control frameworks (the collapse of the INF Treaty, the uncertain future of New START), the proliferation of tactical nuclear weapons lowering the threshold for use, and increasing instability in nuclear-armed states. Cyber warfare and AI-driven decision-making also introduce new failure modes in early warning systems, raising the probability of accidental or miscalculated launches. While humanity possesses the tools to prevent this outcome, the current trajectory of great-power competition, combined with the sheer number of nuclear warheads still in existence (approximately 12,000+), makes nuclear war the single most likely path to global catastrophe.