Early residents of what is now coastal Ecuador and Peru on the west coast of South America knew that bad things often happened to their weather and affected their fishing, and that these “bad things” occurred near the end of the year on a semi-routine basis. 

They called this event “El Niño” (Spanish for “the Boy”), which was later referred to as “Christ Child” because it appeared near the time of Christmas. They did not know what caused the event, but they knew it created extreme hardships to their way of life. Heavy rains inundated their normally arid countryside resulting in widespread flooding and destruction of villages and irrigation canals. Just as importantly, the coastal waters warmed, resulting in the demise of fish and bird life depriving the population of their primary food sources. 

During later years, the El Niño occurrence was scientifically documented but only as a local event. It was found that El Niño is caused by the slacking of steady easterly winds (east to west) routinely blowing across the equatorial Pacific Ocean.  Similar easterly winds in the Atlantic Ocean are called “trade winds” because they brought sailing ships, starting with Columbus, across the Atlantic to the new world.

These steady Pacific easterly winds result in the piling up of water to the west in the vicinity of Indonesia. Along the equatorial west coast of South America, coastal waters are “pushed off” the coast to be replaced with cold subsurface water. This cold, nutrient rich “up-welled” water results in bountiful fish and marine life and a dry coastal environment. 

When the easterly winds across the Pacific slacken, the El Niño event starts. Coastal upwelling decreases, coastal water warms, coastal fish and wildlife die or depart, heavy rains fall over the arid countryside - all resulting in extensive flooding and famine. 

Presently, as with many other large earth cycles and variations, it is not fully understood what causes the decrease of these easterly winds.  It has only been during the past 20 to 30 years that science, with global monitoring satellites, deep ocean weather buoys and powerful computers, has determined the effects of El Niño on weather across the earth.  Such correlations are called “teleconnections” - the effect of an event causing related events elsewhere across the globe.

We now know that El Niño events usually occur every 3 to 5 years – some stronger, some weaker – and that they normally last 9 to 12 months. We know that during such events, Indonesia and northern Australia can experience extreme drought, the Pacific Northwest normally has warm winters, and the southwest United States is wetter than normal.

Closer to home, El Niño episodes result in wetter and cooler winter conditions along the northern Gulf of Mexico coastline and reduced Atlantic hurricane activity. The rapidly developing El Niño this year likely diminished this past season’s Atlantic hurricane activity.

El Niño is perhaps the most well known periodic, large scale event affecting our earth. Its opposite, La Niña, is an ocean cooling event that results in conditions opposite its brother.  There are numerous other earth-related large scale variations and cycles related to hurricanes, droughts, ocean currents, ice ages, global warming and cooling periods, volcanoes spewing out dust - all of which affect our weather and environment.

We are accustomed to short term atmospheric variations. We routinely discuss periods of drought or what seems like weeks of rain or busy or slack cycles of hurricanes. Now we now know some of our abnormal weather might be related to an El Niño event occurring off the coast of South America!
 

NOAA Sea Surface Temperature Analysis from 12/05/06 showing the El Niño of 2006, indicated by the warmer waters along the equator in the central and eastern Pacific Ocean