ENSO is a climactic oscillation of the Eastern Pacific Ocean temperatures called El Niņo Southern Oscillation, more commonly known as El Niņo.   ENSO events have been occurring every 7-10 years since the birth of the Pacific Ocean, and the early explorers had to have encountered a number of them.  It starts when the east-to-west trade winds weaken, and the warm surface ocean water, which is normally held in the west by the wind, begins to flow back to the east.  This in turn prevents the cold water upwelling in the east.  The normally cold water along the California coast is now 8 degrees warmer, and since ocean temperature affects climate, a chain of "abnormal" meteorological events has begun.

The most recent ENSO and the sloppy use of the term "El Niņo" have perversely heightened rather than reduced public misconception of it.  El Niņo is not a weather phenomenon (such as a storm or hurricane), but a climactic oscillation.