<P> Developing countries that are dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are usually most affected . In American Spanish, the capitalized term "El Niño" refers to "the little boy", so named because the pool of warm water in the Pacific near South America is often at its warmest around Christmas . The original name, "El Niño de Navidad", traces its origin centuries back to Peruvian fishermen, who named the weather phenomenon in reference to the newborn Christ . "La Niña", chosen as the' opposite' of El Niño, literally translates to "the little girl". </P> <P> Originally the term El Niño applied to an annual weak warm ocean current that ran southwards along the coast of Peru and Ecuador at about Christmas time . However, over time the term has evolved and now refers to the warm and negative phase of the El Niño Southern Oscillation and is the warming of the ocean surface or above - average sea surface temperatures in either the central and eastern tropical Pacific Ocean . This warming causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia and Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean . The low - level surface trade winds, which normally blow from east to west along the equator, either weaken or start blowing from the other direction . </P> <P> Historically, El Niño events are thought to have been occurring for thousands of years . For example, it is thought that El Niño affected the Moche in modern - day Peru, who sacrificed humans in order to try to prevent the rains . Scientists have also found the chemical signatures of warmer sea surface temperatures and increased rainfall caused by El Niño in coral specimens that are around 13,000 years old . In around 1525 when Francisco Pizarro made landfall on Peru, he noted rainfall occurring in the deserts which subsequently became the first written record of the impacts of El Niño . Modern day research and reanalysis techniques have managed to find at least 26 El Niño events since 1900, with the 1982 - 83, 1997--98 and 2014--16 events among the strongest on record . </P> <P> Currently, each country has a different threshold for what constitutes an El Niño event, which is tailored to their specific interests . For example, the Australian Bureau of Meteorology looks at the trade winds, SOI, weather models and sea surface temperatures in the Nino 3 and 3.4 regions, before declaring an El Niño . The United States Climate Prediction Center (CPC) and the International Research Institute for Climate and Society (IRI) looks at the sea surface temperatures in the Niño 3.4 region, the tropical Pacific atmosphere and forecasts that NOAA's Oceanic Niño Index will equal or exceed + 0.5 ° C for several seasons in a row . However, the Japan Meteorological Agency declares that an El Niño event has started when the average 5 month sea surface temperature deviation for the NINO. 3 region, is over 0.5 ° C (0.90 ° F) warmer for 6 consecutive months or longer . The Peruvian government declares that a coastal El Niño is under way, if the sea surface temperatures in the Niño 1 and 2 regions, equal or exceed + 0.4 ° C for at least 3 months . </P>

Where was the el niño phenomena first recognized