El Niño's coming! Is that so bad?

Sid Perkins

From Boston, at a meeting of the American Association for the Advancement of Science

Recent satellite observations of rainfall patterns over the eastern Indian Ocean hint that the climate phenomenon known as El Niño—typically marked by warming of the equatorial Pacific—will return later this year. Also, although this weather maker is often blamed for droughts, freak storms, and other ill effects, a broader analysis suggests that the United States garners substantial benefits during an El Niño.

Robert F. Adler, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and his colleagues predict a 2002 El Niño based on a numerical index they have developed. When the short-term variation in the amount of rainfall southeast of India increases and the change occurs more frequently in the presence of strong westerly winds, the numerical value of the index goes up.

Over the past 23 years, there have been five El Niños, and Adler's analysis shows that in each case, a spike in the index precedes the onset of an El Niño by 6 to 9 months. More importantly, the index, if it had been used to predict El Niños during that period, wouldn't have generated any false alarms, he says.

The new index breached what the scientists say is a critical threshold in late January. If history holds, a full-fledged El Niño will appear between July and October, says Adler.

That's not entirely bad news. Many people associate El Niño only with damage from severe weather, says David Changnon, a climatologist at Northern Illinois University in DeKalb. Indeed, during the last El Niño—which began in 1997 and was the strongest on record—California suffered more than $1.1 billion in economic losses. Meanwhile, the unusually warm winter that year in the Midwest and along the East Coast cut demand for natural gas and heating oil by 10 percent—a generally ignored savings of about $6.7 billion.

There were other benefits from the 1997 El Niño, says the researcher. Retail sales in the United States were about $5.6 billion higher than normal because of the milder winter. It also allowed more home construction. Fewer transportation delays and less salt used on roads added more savings.

Changnon contends that the overall economic benefits in the United States from that year's El Niño exceeded losses by about $15 billion.

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References:

Adler, R.F. 2002. Satellite observations of variations and extremes in precipitation. American Association for the Advancement of Science Annual Meeting. Feb. 15. Boston.

Changnon, D. 2002. El Niño and the U.S. economy. American Association for the Advancement of Science Annual Meeting. Feb. 16. Boston.

Sources:

Robert F. Adler
Laboratory for Atmospheres
NASA Goddard Space Flight Center
Mail Code 912
Greenbelt, MD 20771

David Changnon
Meteorology Program
Department of Geography
Northern Illinois University
DeKalb, IL 60115-2895

From Science News, Volume 161, No. 9, March 2, 2002, p. 142.