8.2-kiloyear event
▶ Explore on the mapThe 8.2-kiloyear event was an abrupt cooling and drying episode that began about 6200 BCE and lasted roughly two centuries, the most severe climate fluctuation of the Holocene after the ice age. Ice cores from Greenland show a sudden drop in temperature, and pollen records around the Mediterranean, the Sahel and the Arabian peninsula show lakes shrinking and vegetation changing. The cause is usually given as the final drainage of glacial Lake Agassiz into the North Atlantic, which freshened the surface water and slowed the overturning circulation that carries warm water north; other explanations have been proposed, and the timing is still argued. The effects were regional rather than global: settlements in the Near East appear to have been abandoned or reorganised, communities in Greece moved to higher ground, and in China the early cultures of the Yellow river adapted to drier conditions. Because the event falls near the beginnings of farming, it is often discussed as a stress test for early agriculture, though the archaeological signal is uneven and no collapse can be attributed to it with certainty. The event is the standard example of how a change far away, in the meltwater of North America, can reorganise the climate of the whole northern hemisphere.