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These images of sea-surface height relative to normal ocean conditions are evidence of an imminent 'bad' El Niño. A warm water oscillation (white/red) is shown in the equatorial Pacific during March and April this year. The data were collected by the joint US/French TOPEX/Poseidon satellite. Credit: AP/JPL

Predictions that the expected El Niño — the appearance of warm waters off the coast of South America, bringing droughts, storms and floods in its wake — will be stronger than usual are facing scepticism from the countries that could be most strongly affected.

In particular, scientists from Argentina and Peru say they are not yet convinced by reports from the US National Oceanic and Atmospheric Administration (NOAA) that El Niño, which usually occurs in winter every two to seven years, could arrive early, and be the strongest for 25 years.

The forecast, issued on 26 June, says that Indonesia and India are expected to be drier than normal (see panel), while central Chile, Uruguay, southern Brazil, Peru and central Argentina are likely to experience a wetter than normal winter.

But Pablo Lagos, scientific director at the Geophysical Institute of Peru in Lima, is unconvinced. He says it is far too early to take drastic steps, such as changing agriculture patterns, in response to the NOAA prediction. “What is the point of spending so much money if the prediction turns out to be wrong?” he says. “It is better to wait and act only when we are sure.”

Hugo Hordij, director of the Climatic Analysis Centre of Argentina's National Meteorological Service, agrees, adding that he doubts Argentina will be affected by El Niño to the extent predicted by NOAA.

The NOAA prediction was based partly on the abnormally high sea-surface temperatures that have been recorded in parts of the East Pacific, and along and near the west coast of South America. These temperatures continued to increase throughout June, and are now around 2-3°C higher than average.

Such conditions are similar to those observed in 1957 and 1972, both years in which an El Niño event led to droughts near the eastern end of the Pacific Ocean and caused increased rain leading to floods at the western end of the Pacific.

Michael Glantz, a senior scientist at the National Center for Atmospheric Research at Boulder, Colorado, and author of Currents of Change: El Niño's Impact on Climate and Society, believes that the advice given to the governments of Peru and Argentina by their scientists is prudent. “You can't take these predictions at face value,” he says.

“There is no one-to-one correlation between high sea-surface temperatures and an El Niño,” says Glantz. For example, he says, the 1991-92 El Niño was preceded by variable temperatures off the coast of Peru which fluctuated considerably above and below their average values.

Lagos, meanwhile, says that Peru is not wholly disregarding the latest forecast, merely waiting for more precise data. Peru, he says, has a comprehensive two-stage action plan in place, should an El Niño strike. The plan is based in part on the lessons that the country learned in 1982-83, when a lack of preparation for what turned out to be the strongest El Niño since 1950 led to 600 deaths as a result of severe flooding, and US$900 million worth of damage.

The first phase, which Lagos says has already been set in motion, consists of campaigns to make the public aware of the possibility and the possible impact of an El Niño. The second phase starts “once we are more sure about an El Niño”, Lagos adds.

This phase includes drilling into underground water aquifers to ensure clean water supplies, and encouraging the textile industry to ensure that stocks of warm clothing are protected from floods. A law is being considered banning anchovy fishing to conserve depleted fish stocks, which migrate during an El Niño. Farmers, meanwhile, may be encouraged to grow crops that would benefit from a wetter climate.

An El Niño, however, is not all bad news for Peruvian farmers. Some take advantage of the prospect of torrential rainfall by planting copious quantities of seed in desert areas, in the hope of cultivating pastures for their cattle. “Many farmers have already started doing this,” says Lagos.