The Younger Dryas cold reversal

Date

c. 12,900 – 11,700 years ago

Category

Environment & climate

Region

Global (especially North Atlantic)

Era

Prehistory

Significance

Just as the planet was warming out of the last ice age, the Younger Dryas was an abrupt return to near-glacial conditions across the Northern Hemisphere, lasting from roughly 12,900 to 11,700 years ago.

Its onset took less than a century, and it persisted for about 1,300 years before ending equally sharply. The cooling is widely attributed to a disruption of the Atlantic Meridional Overturning Circulation, likely triggered by a vast influx of glacial meltwater that altered ocean salinity and heat transport; a contested minority hypothesis invokes a comet or extraterrestrial impact. Temperatures in the North Atlantic region dropped by several degrees, glaciers readvanced, and vegetation belts shifted. The episode is recorded in Greenland ice cores, ocean and lake sediments and tree rings worldwide. Critically, the Younger Dryas overlaps the period when human communities in the Fertile Crescent (the Natufians) were intensifying their use of wild cereals; many researchers argue that the climatic stress of this cold, dry interval helped push such groups toward cultivation, linking it to the origins of agriculture. The end of the Younger Dryas marks the threshold of the warm, stable Holocene.

Related environment & climate events

• The Pleistocene–Holocene boundary and the start of the Holocene
  c. 11,700 years ago (c. 9700 BCE)
• End of the African Humid Period and Desertification of the Sahara
  c. 3500–2700 BCE
• Late Pleistocene megafaunal extinctions and the overkill-vs-climate debate
  c. 15,000 – 10,000 years ago
• The 8.2-kiloyear abrupt cooling event
  c. 6200 BCE
• The Last Glacial Maximum and human refugia
  c. 26,500 – 19,000 years ago
• The Toba super-eruption and the disputed 'volcanic winter'
  c. 74,000 years ago

Further reading

A New Green History of the World

The wider story

A New Green History of the World

Clive Ponting

The classic accessible account of how environment and climate have shaped human history.

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