El Niño, (Spanish: “The Christ Child”) in oceanography and climatology, the anomalous appearance, every few years, of unusually warm ocean conditions along the tropical west coast of South America. This event is associated with adverse effects on fishing, agriculture, and local weather from Ecuador to Chile and with far-field climatic anomalies in the equatorial Pacific and occasionally in Asia and North America as well. The Oceanic Niño Index (ONI), a measure of the departure from normal sea surface temperature in the east-central Pacific Ocean, is the standard means by which each El Niño episode is determined, gauged, and forecast. El