What is EL Nino?

Simply put by Billy Kessler, an Oceanographer for the Pacific Marine Environmental Laboratory at NOAA-Seatle in his FAQ about El Nino: Suppose a relatively brief opposing wind occurs over the west Pacific warm pool. It may last for as little as one month. This starts and estward current that pushes the warm pool a little bit east of it's usual position. If the ocean and atmosphere were not coupled, then this motion would soon stop when it ran into the trade winds. But we have shown that the trade winds exist because of the temperature contrast between east and west. If the central Pacific is warmed by flow from the west, even a small amount, then the region of rising air will ten to move east with the warm water. That means the trade winds will also shrink back east a little, since those winds are caused by the rising air. But then the pressure of the trades holding up the sea surface slope to the west is weakened, and even more west Pacific water tries to slosh eastward. That wardms the central Pacific a little bit more, and the rising air moves further east, and the trades shrink more. This collapse continues until the water is warm across the Pacific, the trades are weak, and the thermocline zone between the warm upper-sunlit waters and the colder deep-sundeprived watersi and sea surface slope flatten out. b3l7lc
When a cataylist weakens the easterly trade winds around the equator, warm water that is usually stockpiled around Indonesia slowly moves toward the South American coastline. This, in turn, warms the waters off the coast of South America several degrees. Because there is an interaction between the ocean and the atmosphere, the warm water warms the air near to the water. Since warm air rises, this creates instability (as you go up in altitude, air temperatures decrease, but if you get patches of warm air rising into a mass of cool air this causes conflicts or ‘instability' in the atmosphere). Most commonly, this instability influences the production of storms. Also, since the warm water has moved eastward and has taken its storm producing capabilities with it, the path of the Jet Stream, the directions in which storms travel, has also changed. Storms, during El Nino conditions are shot up into the general direction of the U.S. rather than the usual path into Mexico. This was partly why the California area experienced severe flooding during last winter. Because, El Nino conditions, on average, form every 2-7 years around Christmas time, Peruvian fishermen named the event, El Nino or "The Christ Child," in the mid-1500s. However, the event was not recognized as a large-scale event until the 1960s, when satalite technology became available. As mentioned above, the event is triggered by the weakening of trade winds and the mass movement of warm water westward, and, depending on the strength of the event, it continues into mid-Spring, Summer, or Fall time.
El Nino can have many drastic effects on world climate. Huricanes in the Atlantic and Gulf States are surpressed and less numerous than in normal years, and Huricanes and Tropical storms in the Eastern Pacific are more plentiful. Floods can be found in Southern and Central America along with California and the Southwest United States. The Pacific Northwest experiences a warmer winter with less snow and more rain. It has also been found that tornados are somewhats less numerous during the El Nino phenomenon. Coastal errosion can be found all along the North & Central American coastline, as was witnessed by the many homes slowly falling off cliffs in the California area during the major El Nino of 1997-98. Droughts occur in Indonesia and Eastern Australia, as was attested to in the Indonesian fires of 1997-98. Scientists at NASA's Goddard Space Flight Center have also found that El Nino slows the Earth's rotation by an average of 300 to 400 microseconds. At the peak of the most recent El Nino in July 1997, the rotation was slowed by as much as 800 microseconds (almost one thousanth of a second). The success of the Pathfinder mission to Mars was attributed to this slowing of Earth. However, La Nina affects the Earth's rotation causing it to speed up, but only about three-quarters as much as El Nino slowed it down. Indirectly, El Nino causes some rivers to swell, because of increased snow pack and rain. At the peak of the 1997-98 El Nino, 12 people had died while rafting on California rivers alone, more than in the previous four years combined. Fisheries in the Pacific Northwest and South America also disapear because ocean temperatures comonly rise 6-10°F above normal.
Why El Nino forms or what the initial catylist that triggers the conditions is still remains a mystery to the scientific community, although research is currently being conducted by many groups. Theories in the past have included volcanic eruptions, but this has been ruled out because many El Ninos have not been preceeded by eruptions; sea floor venting and sunspots have also been blamed for the rise in temperature shifts, but these predictions have been investigated and have turned up no positive proof.

La Nina

La Nina, in theory, is exactly the opposite of her partner in crime. During a cold event, or La Nina, sea surface temperatures in the Pacific around the equator drop several degrees due to the strenghtening of trade winds. These stong winds cause "upwelling", a process in which nutrient rich water from the bottom of the ocean is brought to the top of the ocean near South America. La Nina, also called El Viejo (the old man) occurs every 4-10 years.
La Nina, opposite not only in principle but also in her effects, causes almost a reverse in climatic conditions around the globe. Historically, La Nina enhances the Huricane season in the Atlantic and Gulf States and surpresses Huricanes and Tropical Storms in the Eastern Pacific. Droughts occur in Southern and Central America along with California and the Southwest United States. The Pacific Northwest experiences a colder winter with more snow at lower elevations. La Nina also been found to enhance the production of tornados from Ohio to the Tennessee River Valley. Mass flooding occurs in Indonesia, Eastern Australia, and Southern Asia. Similarly to El Nino, why La Nina occurs still remains a mystery.

The Future of El Nino & La Nina and Global Warming...

Some scientists feel that the climatic phenomena are becoming more frequent due to global warming. Others feel that El Nino and La Nina are contributing to the warming/cooling of the earth. Still yet, some people believe that the El Nino and La Nina events are simply part of a larger cycle of climatic changes. Unfortunately, we have been studying these events far to short to tell.