Peruvian fishermen noticed that the arrival of El Nino often coincided with the Christmas season so named the phenomenon after the "the baby boy" Jesus. The warmer water of El Nino reduced the number of fish available to catch. The warm water that causes El Nino is usually located near Indonesia during non-El Nino years. However, during periods of El Nino the water moves eastward to lie off the coast of South America.
El Nino increases average ocean surface water temperature in the region. This mass of warm water is what causes climatic change around the world. Closer to the Pacific Ocean, El Nino causes torrential rains across the west coast of North America and South America.
Very strong El Nino events in 1965-1966, 1982-1983, and 1997-1998 caused significant flooding and damage from California to Mexico to Chile. Effects of El Nino are felt as far away from the Pacific Ocean as Eastern Africa (there is often reduced rainfall and thus Nile River carries less water).
An El Nino requires five consecutive months of unusually high sea surface temperatures in the Eastern Pacific Ocean off the coast of South America to be considered an El Nino.
La NinaScientists refer to the event when exceptionally cook water lies off the coast of South America as La Nina or "the baby girl." Strong La Nina events have been responsible for the opposite effects on climate as El Nino. For example, a major La Nina event in 1988 caused significant drought across North America.
El Nino's Relationship to Climate ChangeAs of this writing, El Nino and La Nina do not appear to be significantly related to climate change. As mentioned above, El Nino is a pattern that had been noticed for hundreds of years by South Americans. Climate change may make the effects of El Nino and La Nina stronger or more widespread, however.
A similar pattern to El Nino was identified in the early 1900s and was called the Southern Oscillation. Today, the two patterns are known to be pretty much the same thing and so sometimes El Nino is known as El Nino/Southern Oscillation or ENSO.