 The Younger Dryas was the most recent and longest of several interruptions to the gradual warming of the Earth's climate since the severe LGM, about 27,000 to 24,000 years BP.The change was relatively sudden, taking place in decades, and it resulted in a decline of temperatures in Greenland by 4 to 10°C (7.2 to 18°F) and advances of glaciers and drier conditions, over much of the temperate Northern Hemisphere.It is thought to have been caused by a decline in the strength of the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, in turn thought to have been caused by an influx of fresh, cold water from North America to the Atlantic.