El Niños - What are they?

An El Niño-Southern Oscillation (ENSO) is a naturally occurring climate pattern that is characterized by warming of the ocean surface temperatures in the central and eastern tropical Pacific Ocean. It is considered by climatologists to be one of the most powerful climate driving forces on earth (NOAA). The label "El Nino" comes from fishermen off the coast of South America, who noted periodic warm weather and ocean temperature occurring around Christmas and New Year. El Niño translates to The Little Boy or Christ child in Spanish. ENSO events significantly impact and change weather patterns, ocean conditions, and marine fisheries worldwide and usually occur every 2 to 7 years. Super El Niños usually have a pattern of appearing in multiples of 7, so they can happen every 7, 14, or even 21 years or more. Even though scientists aim to have accurate predictions of when El Niños, especially extreme "super" ones, occur, they are unpredictable forces of nature with unforeseen after effects. Although detailed weather pattern records are an artifact of the 20th and 21st centuries, historic records can be used to look into the recent occurrences and archaeological and paleoclimatic data provide evidence of their occurrence and severity in the more distant past (NOAA). 

In contrast, a La Niña is the reverse of a coastal El Niño, an exaggeration of normal non-Niño conditions. Instead of irregular warming, the Pacific basin cools down. Human consequences of La Niña are much less severe than that of an El Niño.