La Niña, the climate event that causes water to be colder than normal in the eastern Pacific, has now been shown by new research released Monday to be responsible for simultaneous megadroughts in the North and South American Southwest over the past 1,000 years.

Megadroughts are extended periods of drought that last at least 20 years. In a study published in the journal Nature, researchers found that these megadroughts occurred simultaneously in the North American and South American Southwest “regularly” and often during a La Niña event.