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Fact Sheet

Charting El Nino

Satallite photo
A June 2001 NASA satellite image shows what may be the beginnings of an El Nino.  


El Nino, like many weather patterns, is one of those systems that nearly everyone has heard of, but whose origins are not so widely known. An elixir of unusual trade wind patterns and warming waters, the weather event can dominate climatic conditions across the world.

Thank 19th century fishermen for coining the name "El Nino." Fishermen plying the waters off the coast of Peru in the late 1800s were the first to notice an occasional seasonal invasion of warm, southward ocean current that displaced the north-flowing, cold stream in which they normally fished. Typically, it happened around Christmas, or the first of the year hence the name "El Nino," which means "little boy" or "Christ child" in Spanish.

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  • El Nino has been falsely linked to global warming and unfairly blamed for hurricanes in the Atlantic, and properly takes credit for droughts in Australia and floods in California. It also is responsible for regional depletion of fish stocks and fluctuations in seasonal temperatures.

    An El Nino occurs when the ocean-atmosphere system in the tropical Pacific Ocean is disrupted. Normally, trade winds blow toward the west across the tropical Pacific Ocean, piling up warm surface water in the west Pacific. In a classic El Nino, the trade winds relax in the central and western Pacific, leaving warm water in the east Pacific. Heavy rainfall follows the warm water eastward, leading to flooding in Peru and California, among other places. Meanwhile, areas far to the west, such as Indonesia and Australia, suffer droughts.

    Notable effects attributed to El Nino in 1997-98 

    Displacing heat in the east Pacific also prompts changes in the global atmospheric circulation, meaning changes in weather in regions far removed from the Pacific. The alteration in water temperature also affects fish reproduction, which has repercussions along the aquatic food chain.

    El Ninos occur about every four years, with the most recent episode occurring in 1997-98. The 1983-84 El Nino is considered the strongest and most devastating on record, responsible for more than 1,000 deaths, causing weather-related disasters on nearly every continent and totaling $10 billion in damages to property and livestock.

    El Nino conditions typically last one or two years, and are usually followed by "La Nina," or "little girl," in which a cooling of those same mid-Pacific waters triggers a reversal of climate impacts.


    El Nino appears to be living up to its four-year cycle, say scientists, who last month cited a "steady evolution" of signs that point to a return of the weather event. Foremost is the warming of temperatures in the mid-Pacific Ocean.

    "This warming represents an early stage of El Nino's onset," said Vice Adm. Conrad C. Lautenbacher Jr., head of the National Oceanic and Atmospheric Administration, which employs an array of experts and tracking equipment to follow El Nino and other patterns. "If the warming persists, it will be several more months before mature El Nino conditions develop."

    Information from heat-sensing satellites and a network of monitoring buoys across the Pacific shows sea-surface temperatures in the past year have jumped roughly 2 degrees Celsius, from slightly below normal to slightly above normal, NOAA said. Such a change often indicates El Nino is on the way.

    Some events already hint that it may be here already. Officials in Thailand, the world's top rice exporter, blamed El Nino for a looming drought, which could force farmers to cut rice production. And in Australia, the national Bureau of Meteorology said the odds this year of an El Nino occurring in the tropical Pacific region were double the normal level of risk.

    It is too early, say specialists, to predict how pervasive this latest El Nino could be.


    Is it too early to predict how pervasive this latest El Nino could be?

    Can El Nino be predicted?


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