The El Nino Effect
Nature's footnote to the end of the last millennium, the 1997-98 El Nino wreaked havoc with global climate patterns and brought chaos to the world. In Ecuador alone, floods and landslides killed more than 220 people and made 30,000 families homeless. The infrastructure, too, was severely damaged as the storms washed away more than 1600km of main roads, 11,000km of secondary roads and over fifty bridges. In the worst affected coastal areas, cases of hepatitis, cholera, malaria and dengue fever escalated. As all the Pacific countries affected by El Nino pick up the pieces, conservative estimates of the cost of reparation is at around US$20 billion. The phenomenon itself is no new thing. Records document such events over 400 years ago, but it was only in the 1960s that the Norwegian meteorologist, Jacob Bjerknes, identified the processes that lead to an event. He saw that the El Nino - meaning "the Little Boy" or "the Christ Child", a name given by Peruvian fishermen to the body of warm water that would arrive around Christmas - was intimately connected to extremes in the so-called Southern Oscillation , wherein atmospheric pressures between the eastern equatorial Pacific and the Indo-Australian areas behave as a seesaw, the one rising as the other falls. In "normal" years, easterly trade winds blow across the Pacific, pushing warm surface water westwards towards Indonesia, Australia and the Philippines, where the water becomes about 8°C warmer and about half a metre higher than on the other side of the ocean. Back in the east, the displacement of this water allows the cold, nutrient-rich water, known as the Humboldt or Peru Current, to swell up from the depths along the coast of South America, providing food for countless marine and bird species. An El Nino event , however, occurs when the trade winds fall off and the layer of warm water in the west laps back across the ocean, warming up the east Pacific and cooling the west. Consequently, air temperatures across the whole of the Pacific begin to even out, tipping the balance of the atmospheric pressure seesaw, which further reduces the strength of the trade winds. Thus the process is enhanced, as warm water continues to build up in the eastern Pacific - bringing with it abnormal amounts of rainfall to coastal South America, whilst also completely starving other areas of precipitation. The warm water also forces the cold Humboldt current and its micro-organisms to deeper levels, effectively removing a vital link in the marine food chain, killing innumerable fish, sea birds and mammals. Meanwhile, the upset in the Southern Oscillation disturbs weather systems around the world, resulting in severe and unexpected weather. In the past twenty years, El Nino-Southern Oscillation ( ENSO ) events seem to have become stronger, last longer and occur with greater frequency, leading many to suggest that human activity, such as the warming of the earth's atmosphere, through the greenhouse effect, could well be having an influence. If this is true, failure to cut emissions of greenhouse gases may in the end cost the lives and livelihoods of millions of people across the world.
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