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El Nino

While some forecasting methods had limited success predicting the 1997 El Nino a few months in advance1, the Columbia University researchers say their method can predict large El Nino events up to two years in advance. That would be good news for governments, farmers and others seeking to plan for the droughts and heavy rainfall that El Nino can produce in various parts of the world.

Using a computer, the researchers matched sea-surface temperatures to later El Nino occurrences between 1980 and 2000 and were then able to anticipate El Nino events dating back to 1857, using prior sea-surface temperatures. The results were reported in the latest issue of the journal Nature.

The researchers say their method is not perfect, but Bryan C. Weare, a meteorologist at the University of California. Davis, who was not involved in the work, said it “suggests2 El Nino is indeed predictable.”

“This will probably convince others to search around more for even better methods,” said Weare. He added that the new method “makes it possible to predict El Nino at long lead times3.” Other models also use sea-surface temperatures, but they have not looked as far back because they need other data, which is only available for recent decades, Weare said.

The ability to predict the warming and cooling of the Pacific is of immense importance4. The 1997 El Nino, for example, caused an estimated $20 billion in damage worldwide, offset by beneficial effects in other areas, said David Anderson, of the European Centre for Medium-Range Weather Forecasts in Reading, England. The 1877 El Nino, meanwhile, coincided with a failure of the Indian monsoon and a famine that killed perhaps 40 million in India and China, prompting the development of seasonal forecasting, Anderson said.

When El Nino hit in 1991 and 1997, 200 million people were affected by flooding in China alone, according to a 2002 United Nations report.

While predicting smaller El Nino events remains tricky, the ability to predict larger ones should be increased to at least a year if the new method is confirmed.

El Nino tends to develop between April and June and reaches its peak between December and February. The warming tends to last between 9 and 12 months and occurs every two to seven years.

The new forecasting method does not predict any major El Nino events in the next two years, although a weak warming toward the end of this year is possible.

1. The method used by the Columbia University researchers can predict El Nino a few months in advance.

A Right B Wrong C No mentioned

2. The Columbia University researchers studied the relationship between the past EI Nino occurrences and sea-surface temperatures.