The Younger Dryas
The world falls back into near-glacial cold for 1,200 years, then exits it within a decade.
- When
- —
- Duration
- 1.2 thousand years
- Known to
- ± 100 years
- Era
- Late Pleistocene, Quaternary
About 12,900 years ago the warming reverses sharply and the Northern Hemisphere returns to cold, dry, glacial-like conditions for roughly 1,200 years. The leading explanation is a freshwater flood from the collapsing Laurentide ice sheet shutting down Atlantic overturning circulation; a comet impact has been repeatedly proposed and repeatedly failed to hold up, and recent work points to volcanic forcing at the onset. Its end, around 11,700 years ago, is abrupt — Greenland warms about 10 degrees within a few decades — and that moment defines the start of the Holocene.