What Is El Niño?

El Niño (Spanish word for male child) is a naturally occurring event in the equatorial region which causes temporary changes in the world climate. El Niño refers to a whole complex of Pacific Ocean sea-surface temperature changes and global weather events. The ocean warming off South America is just one of these events. Every three to seven years, an El Niño event may happen during many months to more than one year causing economic and atmospheric worldwide. The worst El Niño occurred in 1997-1998.
In contrast, La Niña (Spanish word for female child) refers to an anomaly of unusually cold sea surface temperatures found in the eastern tropical Pacific. La Niña occurs roughly half as often as El Niño.