Climatologists are already confident this will rank as at least the second worst El Nino this century, if not the worst. The current record holder, which happened from 1982 to 1983, is estimated to have killed 2,000 people and caused more than pounds 5bn worth of damage.
"This one is well underway and it's proving to be a very large event,'' said Mike Davey, the El Nino expert at the Meteorological Office's Hadley Centre for Climate Prediction in Bracknell, Berkshire.
Taking no chances, the South African Cabinet decided yesterday to start preparing. A special committee for disaster management was set up, and an urgent meeting of African ministers convened. Ministers said a severe drought was expected from November to March 1998.
In a world where the key natural resources of freshwater, fertile soil and forests are squeezed by a rising human population, drastic departures from normal weather patterns become more damaging. Yet some scientists believe that global warming, caused by mankind changing the make-up of the atmosphere, may itself be exacerbating the natural climate oscillation of El Nino which has been going on for thousands of years, increasing its threat.
In the last few years, El Nino has moved out from the lecture halls and laboratories of climate science and academia into the wider world.
The phenomenon lasts from two to five years and begins roughly every five years. Normally, in the absence of El Nino, the trade winds blowing across the Pacific from east to west "bunch up" warm, surface waters on the western side of the Pacific. The sea level there is several feet higher than on the east, and the sea temperatures are also higher. Along the South American coast, cold waters well up from deep ocean trenches, helping to maintain this temperature difference across 9,000 miles of ocean.
El Nino erases this difference. When it starts, usually around June, the trade winds slacken and the sea surface temperatures in the central and eastern Pacific begin to rise. What begins this process is not known (and its onset cannot yet be accurately predicted) but it is a positive feedback - the rising sea temperatures tend to weaken the trade winds, which in turn raises the temperatures further.
Scientists using satellites and sensor buoys spot the phenomenon as a fast growing area of surface water where the temperature is several degrees warmer than it should be for the time of year. This temperature "anomaly" grows in area and depth, soon covering sea the size of a continent. By Christmas it is pressed up against hundreds of miles of Ecuador and Peru; people there named it "the boy child" after Jesus. The ocean upwelling slows down, the surface water is as much as eight degrees warmer than normal, and the fishing is severely disrupted.
Onshore there is extremely heavy rainfall. The effects swiftly spread to other continents as the atmosphere and winds respond to the change in sea temperatures. On the other side of the Pacific, drought has already hit large areas of South East Asia and Australia - and El Nino is being blamed. Dr Davey said its impact on weather was heaviest around the Pacific rim, but it could be seen in Africa and as far north as Alaska. One of the few places where no climatologist can confidently claim El Nino is at work, at least as yet, is Europe. In Australia, a government-backed forecasting organisation is predicting that the country's next wheat harvest could be slashed by one sixth because of the resulting drought. And in South Africa, Agriculture Minister Derek Hanekom said last week that the expected onset of El Nino-related drought could halve the country's corn crop, costing more than 1 billion rand (pounds 130m) in lost exports.
David Lubin, economic adviser for emerging markets at banking group HSBC in London, said: "No one is able to identify the global effects but the basic picture is that prices will go up, incomes will go down and trade balances will be hit." There are worries about how El Nino will affect cocoa, coffee and tea harvests. At the world's biggest futures exchange, the Chicago Board of Trade, some traders have already noticed abnormally large price hedging.
El Nino will be threatening southern hemisphere maize and wheat harvests just after world grain reserves have begun to recover from a couple of lean years which have sent international prices soaring.
In Indonesia, fires used to clear brushwood from plantation sites have gone out of control due to the dry conditions, and El Nino is blamed again. A pall of smoke and haze has covered Singapore and swathes of Malaysia as well as much of Indonesia, threatening the health of millions of people and closing airports. In Papua New Guinea, villagers are leaving their homes in the highlands and traditionally prized pigs are being sold to buy food as a drought continues.
In the country closest to the phenomenon, Peru, the Central Bank forecast a slowdown in economic growth to 5 per cent next year from 6 per cent in 1997 because of likely flooding along the northern coast, droughts in the southern highlands and reduced fish catches.
Weather, The Eye,
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