El Nino, the periodic warming in the equatorial Pacific that can change weather worldwide, is more predictable than previously thought, researchers report.
While some forecasting methods had limited success predicting the 1997 El Nino a few months in advance, the Columbia University researchers say their method can predict large El Nino events up to two years in advance.
That would be a boon for governments, farmers and others seeking to plan for the droughts and heavy rainfall El Nino can produce in various parts of the world.
Able to anticipate
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 Thursday’s issue of the journal Nature.
The researchers say their method is not perfect, but Bryan Weare, a meteorologist at the University of California, Davis, who was not involved in the work, said it “suggests El Nino is indeed predictable.”
“This will probably convince others to search around more for even better methods,” said Weare.
The new method “makes it possible to predict El Nino at long lead times,” said lead author Dake Chen of Columbia University’s Lamont-Doherty Earth Observatory.
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, Chen said.
Human, financial costs
The ability to predict the warming and cooling of the Pacific is of immense importance.
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, Anderson wrote in an accompanying commentary.
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.
Chen said 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.