Wakeup Call

By the early 1980s researchers had effectively confirmed Jacob Bjerknes's earlier insights on how an El Niño event tends to evolve. Scientists analyzing data covering six El Niños from 1950 to 1976 found that in December or January sea surface temperatures off Peru would begin to rise but, unlike in "normal times," would not drop as the Southern fall season (February-April) progressed. These anomalously warm temperatures would gradually migrate westward, growing warmer as they did so. The warm waters in the eastern Pacific would eventually lower atmospheric pressure, thereby causing the trade winds to collapse, and around the end of the year sea surface temperatures in the central and eastern Pacific would peak. This phase of El Niño would typically last into spring in the northern hemisphere, where its effects were felt most strongly. Finally, sea surface temperatures in the central Pacific would begin to cool and El Niño would bow out and be replaced either by La Niña or by average conditions.

However, when the severe El Niño struck in 1982 to 1983, its timing was unusual. This tempest did not show the typical warming of waters off Peru around April. Hindsight now shows that El Niño's signs were evident by July 1982. Unfortunately, satellites making measurements of sea surface temperature in the Pacific were confounded by the April eruption of El Chichon volcano in Mexico, which had spewed a massive cloud of fine particles high into the atmosphere. To the satellites, sea surface temperatures appeared much colder than they actually were. Although the equatorial buoys were in place, measurements from them were available only after the instruments were recovered months later. As a result, scientists were virtually blind to the coming threat.

Australia, already in the grip of its worst drought of the century, suffered wildfires and catastrophic agricultural and livestock losses that together cost billions of dollars of lost revenue and damage. Drought racked much of sub-Saharan Africa, forcing even normally food-exporting nations such as the Republic of South Africa and Zimbabwe to turn to the international community for help. In parts of southern Ecuador and northern Peru, up to 100 inches of rain fell during a six-month period. Swollen rivers carried a thousand times their normal flow. In all the event was blamed for nearly 2,100 deaths worldwide and forced hundreds of thousands of people to be evacuated, left thousands more homeless, and caused over $13 billion in damage worldwide.

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