<P> During strong El Niño episodes, a secondary peak in sea surface temperature across the far eastern equatorial Pacific Ocean sometimes follows the initial peak . </P> <P> ENSO conditions have occurred at two - to seven - year intervals for at least the past 300 years, but most of them have been weak . Evidence is also strong for El Niño events during the early Holocene epoch 10,000 years ago . </P> <P> El Niño may have led to the demise of the Moche and other pre-Columbian Peruvian cultures . A recent study suggests a strong El - Niño effect between 1789 and 1793 caused poor crop yields in Europe, which in turn helped touch off the French Revolution . The extreme weather produced by El Niño in 1876--77 gave rise to the most deadly famines of the 19th century . The 1876 famine alone in northern China killed up to 13 million people . </P> <P> An early recorded mention of the term "El Niño" to refer to climate occurred in 1892, when Captain Camilo Carrillo told the geographical society congress in Lima that Peruvian sailors named the warm north - flowing current "El Niño" because it was most noticeable around Christmas . The phenomenon had long been of interest because of its effects on the guano industry and other enterprises that depend on biological productivity of the sea . </P>

What are the effects of an el nino