The prolonged absence of sufficient water — through deficient rainfall, depleted groundwater, or both — that has collapsed civilizations, driven mass migration, and shaped the political geography of every inhabited continent, and whose intensification under climate change is making it one of the defining crises of the twenty-first century.
Every major civilization has a drought story. The Akkadian Empire. The Maya. The Bronze Age Collapse. The Dust Bowl. Drought is the most politically dangerous form of climate — it moves slowly enough to trap people, fast enough to destroy what they depended on. And it is getting worse.