Younger Dryas
The last glacial maximum (LGM) was about 27,000 to 24,000 years ago. The Younger Dryas was the most recent and longest of several interruptions to the gradual warming of the Earth's climate. The change was relatively sudden, and it resulted in a decline of temperatures in Greenland by 4 to 10 °C (7.2 to 18 °F) Glaciers and dry conditions spread over much of the temperate Northern Hemisphere. It may have been caused by an influx of fresh, cold water from North America to the Atlantic.