El Niño is a periodic climate condition that occurs an average of every five years. It is strongest in the Pacific but has global ramifications. Caused when a dominate high pressure system over the Pacific collapses, it causes wind directions and ocean currents in the Pacific to change direction, throwing off prevailing winds and bringing drought to Indonesia, Southeast Asia, southern Africa and Australia, heavy rains and floods to Peru and east Africa, typhoons to Japan, stormy weather to the United States and disruptions to monsoons in India. [Source: Curt Suplee, National Geographic, March 1999]

The name El Niño (Spanish for "the Christ Child") was coined by Peruvian fishermen in the port of Callao north of Lima in early 1970s because the warm air and water associated with change usually first appeared around Christmas. In the 20th century there were 23 El Niños and 15 La Niñas. During the 50 years period between 1950 and 2000, El Nino condition existed 31 percent of the time and La Niña conditions existed 23 percent of the time.

Severe El Niños are though to contributed to the decline and fall of the Moche civilization in Peru around A.D. 500. It also probably created smooth sailing across the Pacific for Magellan in 1520, In 1630, 5 million people died in India from an El Niño-induced drought and famine. During an El Niño that lasted from 1789 to 1793 the flow of the Nile was greatly reduced and 600,000 people died in India.

Scientist have said that El Niños have been getting progressively worse. More powerful and far-reaching than originally suggested, the El Niño of 1982-83 was the strongest of century until that time. It was still creating havoc in 1990s. After that El Niños have been more frequent. The 1997-98 El Niño was the worst on record.

Normal Trade Wind Conditions

Under normal conditions the trade winds blow from east to west across the equatorial Pacific. They are generated by a low pressure system around Indonesia and Australia caused by warm that rises thousands of feet upwards. As it rises and cools it produces rain. High in the atmosphere the air moves from west to east — the opposite direction of the trade winds — pushed by up upper atmosphere winds. The air becomes cooler and heavier as it moves eastward, When the air reaches the Americas it is cold and heavy enough so that it sinks, creating a high pressure system there.

As the trade winds blow from east to west the wind pushes the ocean surface along with them. As a result of this the sea level in Asia is about 18 inches higher than seas along the coast of South America. Because the ocean is lower along the South American coast than it is further to the west, water from deep in the ocean rises up and displaces the missing water. The cooler water is full of nutrients that feed plankton, which in turn feed some of the world's richest fisheries. The thermocline (the depth where surface water and cold deep water meet) also rises bringing even more nutrients.

The trade winds create a balance between the warm waters of the western Pacific and the cool water of the eastern Pacific. Sun heats the waters in the eastern Pacific but the thermocline is only about 40 meters below the surface. Storm clouds form over warm water surfaces in the western Pacific. The winds pick up moisture as they blow across the ocean and releases in the form of south-west monsoon rains in Indonesia, Papua New Guinea, northern Australia and parts of Southeast Asia and the Philippines.

The coastal regions of northern Chile and Peru are among the driest regions on earth because the trade winds blow Pacific moisture away and the Andes block moisture from the Amazon region.

Oceans are the largest sources of atmospheric heat. Water vapor produced by transpiration of heat and evaporation produces more clouds and heat that disrupts patterns around the globe in ways still not completely understood.

El Niño Development

El Niños generally occur an average of once every five years within a three to seven year period. Still there are great fluctuations and El Ninos are difficult to predict. Each El Niño is different and local conditions can change dramatically in single place over a few days.

El Niño are caused when a dominate high pressure system over the Pacific collapses, causing wind directions and ocean currents in the Pacific to change direction. Instead of coming from the east the winds start comings from the west, thrown offing all kinds of things.

El Niños start when prevailing easterly trade winds slacken as air pressure become abnormally low around Tahiti and an unusually high pressure develops over Australia. Warm water from the western Pacific starts flowing eastward, creating a band of warm water that spans the equatorial Pacific. Oceans begin warming up in March or so and then slacken off and gain momentum in September and reach their peak around December.

As the trade winds weaken seawater and moisture-laden clouds don’t move westward. This means that areas that rely on southwest monsoon experience drought. Warner waters in equatorial Pacific cause a low pressure system to form there and dry air descends over Australia and Indonesia, causing drought.

Why a low pressure forms over Tahiti and a high pressure forms over Australia and trade winds slacken is still kind of a mystery. Among the variable that play a part in the complex mechanisms are the Earth’s orbit, strength of ocean currents and possibly global warming.

El Niños contains the seeds for their own destruction. They brings drier, hotter air to the south and wetter, colder air to the north, which eventually lead to their demise.

Meteorologists at the Research Institute for Global Change in Yokohama, Japan have found that the presence of a weather condition in the Indian Ocean — the negative phase of the so-called Indian Ocean Dipole, when warn water occurs in the east and cold water in the east — often occurs a year before El Nino events in the Pacific.

Effects of El Niño

El Niño throws off weather patterns worldwide. In Tahiti, which normally sits under a fair weather high pressure system, waves of typhoon start rolling in. Pacific storm lash the northwest United States and drought descends on Australia, Indonesia, Southeast Asia and as far west as Southeast Africa.

El Niño brings: 1) drought to Indonesia, Southeast Asia, the Philippines and Australia; 2) heavy rains to the west coast of South America; 3) stormy wether and milder winters to western United States; 4) droughts to southern Africa; 5) fewer hurricanes to the Atlantic; 6) heavy rains to eastern Africa; and 7) disruptions to the monsoon cycle in India.

The effects can be far-reaching. During El Niño years temperatures are usually warmer in Japan, India, Alaska. The eastern United States has a warmer-than-normal winters and there are droughts in northeast Brazil. Drought-stricken areas in Indonesia, Southeast Asia, Australia, Papua New Guinea and Brazil often times experience ravaging forest fires.

Effects of El Niño on the Americas

The layer of warm water caused in the equatorial Pacific by El Nino, typically about 175 meters thick, flows over colder, nutrient-rich water and blocks normal upwelling along the North and South American coasts. Sea life there experiences shortages of food. As warm water moves toward South America, heat and moisture from the warm seas rise, producing storm clouds and bringing heavy rainfalls to the Americas.

Along the Equator, where cloud formation is already intense due to the convergence of northern and southern trade winds more clouds than usual develop. Drawn south by by lower atmospheric pressure, the Pacific jet stream intensifies and moves southward, bringing major storms to Mexico and the western United States.

The polar jest stream in the United States moves further north, keeping cold dry air out of the eastern United States. The jest stream shears of the tops of westward-moving Atlantic storms, decreasing the development of Atlantic hurricanes. On the dry west coast of the Americas: instead of cold water being blown away from the continent, warm water gets blown towards it, causing torrential rainstorms.

Off the west coast of the United States and South America, the unusually warm waters and changes in ocean currents dispute fisheries as fish seek colder more nutrient-rich waters. This has severe consequences on people and animals that depend on the fisheries. Fishermen go broke and seas lions and other animals starve to death.

La Niña

El Niña refers to a cooling of the mid-Pacific equatorial region as seawater there cools to temperatures below normal. It often occurs in years following El Nino. The effects are often opposite those of El Niño: floods occurring in places where droughts occurred under El Niño and cold winters occurring where mild winters occurred under El Nino.

La Niñas are like El Niños in reverse. They start when prevailing easterly trade winds intensify as air pressure become abnormally high around Tahiti and an unusually low pressure develops over Australia. The strong trade winds push the water westward. Warm waters flow towards Asia. Cold, deep water upwells to the surface along the Americans. The cool water dilutes the warmer liquid at the surface, causing the temperatures to drop. Nutrients become more plentiful and evaporation decreases, reducing rain and cloud formation in the eastern Pacific. With more warm water pushed to the western Pacific, storm clouds intensify there and bring more rain to Indonesia and Southeast Asia.

La Niñas tend to develop from March to June and reach the peak of their intensity at the end of the year. The phenomena is linked to fewer typhoons in the Pacific but more in the Atlantic. In the Pacific a “cold water tongue” stretches along the Equator from Ecuador to Samoa. The equatorial cloud formation there becomes split, separated by the Tahiti high. The Pacific subtropical jet stream is similarly split and weakened, allowing Atlantic hurricanes to move westward and gain strength.

La Niña brings higher temperatures and more rainfall to Australia, Indonesia and Southeast Asia and causes heavier rainfalls in the monsoon season in India and wetter than normal condition as far west as Africa. In the Western hemisphere, the polar jet stream moves southward bringing cold temperatures to the northern United States. The weak subtropical jet stream weakens causing less ran in the Gulf of Mexico and the southeast United States.

La Niña and El Niño are like a pendulum that goes back and forth. There were La Niñas after the El Niños in 1982-83 and 1986-87 A La Niña occurred in late 2005 and early 2006 and occurred after the El Niño ended in 2007

El Niño 1997-98

A mild El Niño occurred in late 2006 and early 2007 and late 2009. There were also mild El Niños in 1986-87, 1991-92 and 1995.

The 1997-98 El Niño was the worst of record. Producing as much energy as a million Hiroshima bombs, it killed an estimated 2,100 people and caused $33 billion in damage. Some attributed 21,000 death to the phenomena.

The El Niño of 1997-98 caused a multitude of unusually powerful cyclones and typhoons, compered to only a few in previous years, in the Pacific and flash floods in Peru and Ecuador. More than 80 people were killed by mudslides, flooding and disease in December 1997 and January 1998.

During the 1997-98 El Niño the waters off Peru's northen coast were up to 10 degrees warmer than usual. The result was heavy rain. Parts of the Nazca Lines were washed away. People worried about flash floods camped out on their roofs. Major highways were washed out, making delivery of emergency supplies nearly impossible. Cholera outbreaks occurred in the cities. The weather became the highest-rated shows on both television and radio. More than 200 people were killed and hundreds of thousands of homes were destroyed.

Torrential rains caused by the 1997-98 El Niño left 120,000 people homeless in Ica (4 hour south of Lima). 'We woke up in hell — or at least some kind of bad movie," one Ica resident told the Washington Post. "The river banks broke, and the water poured out in currents. It carried me down for blocks until I hit the walls of the school. I was screaming for my children. Everyone was screaming. We had a neighborhood here but now we just have a bunch of rocks and sticks.”

On islands off of California, the mortality rate among sea lion pups was 70 percent, compared to 25 percent in normal years, as warm waters caused the squid and small fish the sea lions feed on to swim deeper in the ocean to reach of cooler, nutrient-rich waters, beyond the sea lion’s rage. In drought-stricken Brazil there were devastating fires and violent demonstrations by farmers demanding aid.

Smoke from fires caused by droughts in Indonesia reduced air visibility to less than half a mile hundreds of miles away in the Maldives. In Mongolia an unusually high temperature of 108 degrees F was recorded. Central France recorded record floods. Madagascar was hit by devastating cyclones.

El Niño 1982-83

The 1982-83 El Niño caused 2,000 deaths and $13 billion worth of damage world wide It was the strongest on record up to that time. Sea temperatures were as high as 18 degrees F above normal and droughts and storms were catastrophic.

In Peru, the 1982-83 El Niño left 300 people dead and caused $1 billion in damage. The north was hit by floods and landslides. The disappearance of fish stocks caused the economy to plummet 12 percent. The event caught scientist by surprise. The weather effects were at their peak before the sea temperature changes were observed.

Three months before Christmas in 1982 a layer of warm water, 450 feet thick, arrived off the coast or Ecuador and Peru, smothering the cool water current which dominates the region. The fish vanished and the simmering sea started cooking up batches of storms. Places that normally measured rain inches were drowned by ten feet.

In the 1982-83 El Niño raging rivers poured through the streets of Chulliyachi, Peru, killing people and destroying homes. Six meter waves washed away entire blocks, food was airlifted to people on high ground and rescue workers evacuated 1,500 by air. The residents were so traumatized they set up a new town a mile away. Parts of the city of Tumbes where under water for eight months.

The 1983 El Niño had a surprising consequence. The nutrient rich runoff from the swelled rivers fueled an explosion of shrimp off the coast. Fisherman that switched to shrimpers made a fortune.

A 1972 El Niño caused the herding anchovies into a pocket of cold water near the coast. Fishing vessels descended on the trapped fish as if they were a merciless conquering army. As much as 180,000 tons of fish were harvested a day. The fish and birds have never recovered. Some of the world's largest schools were gone and the fishing towns became ghost towns. For a while sardines replaced the anchovetas, but they too are now gone. [Source: Thomas Y. Canby, National Geographic, February 1984]

El Niño and Global Warming

El Niños occurs on average every four or five years but over the past couple of decades they seem to be occurring more frequently. Some scientists believe that this is because of global warming. In the early 1990s there were several El Niño in a row. After dying down in 1995 and 1996 another one appeared in 1997-98 El Niño. The increased intensity of the El Niños is also blamed on global warming.

The relationship between El Niño and global warming is being researched but is still not understood. Scientists are trying to pin down if global warming will lead to more and stronger El Ninos that could cause more droughts, fires and crop failures.

Scientists are investigated El Niño by using oil drills to take core staples from coral reefs in the middle of the Pacific. Bleached layers of coral strata caused by the warming of waters in El Niño years indicate when past El Niños have taken place in the past. This research seems to indicate that after 1880 El Niños began occurring once every 4.9 years compared to every 7.5 years before 1880 (with La Niñas every 4.2 years, compared to once a decade).

Studying El Niño

El Niño and La Nina are monitored with satellites and buoys that measure ocean temperatures. After th El Niño of 1982-83 caught everyone by surprise, the National Oceanic and Atmospheric Administration (NOAA) launched the tropical atmosphere/ocean array program to measure and predict future El Niños. It consists of 70 anchored buoys that span the equatorial pPacific, the buoys measure air and wind conditions at the surface and sea temperatures to a depth of 1,600 feet with the data submitted to satellites and to NOAA’s Pacific Marine Environmental Laboratory in Seattle.

The U.S.-French TOPEX/Poseidon satellite orbits the Earth at a height of 830 miles, measuring sea-surface elevation and information about ocean circulation, including enormous rhythmic sloshing called Kelvin and Rossby waves that travel back and forth across the entire Pacific.

Data from the buoys, satellite, research hips and other sources is arranged in complex models and fed into supercomputers to predict future El Niños. The processes are so complex it is difficult enough to predict general trends and almost impossible to predict th waether in a specific location. When such prediction are made sometimes floods appear in places that were predicted to have drought and visa versa.

Scientists are also pouring over historical records and available data from the past to get statical likelihoods for events. There is evidence that coastal communities that lived in Peru 13,000 years knew of El Ninos and the Incas made adjustments for them. Adm Giampietr Rojas of Peru’s Institute of the Sea told National Geographic, “They built their cities on the tops of hills, and the population kept stores of food in the mountains. If they built on the coast , it was not near the rivers,” usually the most logical location. “That’s why so many of their dwellings are standing today.”

Image Sources: World Meteorological Organization; National Oceanic and Atmospheric Administration (NOAA), Wikimedia Commons

Text Sources: World Meteorological Organization; National Oceanic and Atmospheric Administration (NOAA), New York Times, Washington Post, Los Angeles Times, Times of London, Yomiuri Shimbun, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

Last updated January 2012

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