[2] The term was first used by Connie Woodhouse and Jonathan Overpeck in their 1998 paper, 2000 Years of Drought Variability in the Central United States.
[2] Benjamin Cook suggested that the definition be a drought which is exceptionally severe compared to the weather during the previous 2,000 years.
[4] Past megadroughts in North America have been associated with persistent multiyear La Niña conditions (cooler than normal water temperatures in the tropical eastern Pacific Ocean).
[5] Megadroughts have historically led to the mass migration of humans away from drought affected lands, resulting in a significant population decline from pre-drought levels.
They are suspected of playing a primary role in the collapse of several pre-industrial civilizations, including the Ancestral Puebloans of the North American Southwest,[6] the Khmer Empire of Cambodia,[7] the Maya of Mesoamerica,[8] the Tiwanaku of Bolivia,[9] and the Yuan Dynasty of China.