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A Weather Phenomenon

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Vehicles were tossed about inside homes as several tornadoes tore through central Florida in February 1998. (Reuters)

Explaining El Niño

By Curt Suplee
Washington Post Staff Writer
Autumn 1997

(Editor's note: The following article was written entering the 1997-1998 El Niño season.)

There's trouble in the air. Specifically, in the air off the west coast of the Americas, where the sea surface has been heated to abnormal extremes by an ominous, intermittent flood of hot water called El Niño.

The last time conditions looked like this was when the strongest, most destructive El Niño on record struck in 1982-83. By the time that event subsided, some 2,000 people had died in flooding, mud slides, droughts, fires and sundry related calamities, hundreds of thousands were forced out of their homes, and economic losses topped $8 billion worldwide -- $1.5 billion in the United States.

This year's version promises to approach or even equal 1982-83, which climate researcher James J. O'Brien of Florida State University's Center for Ocean-Atmospheric Prediction Studies (COAPS) calls "the mother of all Los Niños." Already, El Niño has begun to have dramatic effects in some parts of the world and the UN-sponsored World Climate Research Programme warns it "could be the climatic event of the century."

"This one leapt out of the starting blocks," said Ants Leetmaa, director of the National Weather Service's Climate Prediction Center. "By this summer it was ahead of all the others we've seen" since 1950 in terms of early and strong sea-surface warming.

Unlike 1982-83, the world has advance warning this time and the opportunity to protect itself. The threat of a repeat has prompted a rush of scientific symposiums, congressional hearings and anxious regional palavers from Zimbabwe to Australia to flood-leery California,
Pacifica, Calif/AFP
Heavy mudslides cause houses along a cliff in Pacifica, Calif., to begin slipping off the edge in February 1998. (AFP)
where a federal-state "El Niño summit" has been scheduled for next month in Los Angeles. "We're preparing for the worst, but hoping for the best," said Douglas P. Wheeler, California's secretary for resources.

In addition, the likely ferocity of this year's event has scientists wondering whether the frequency and intensity of El Niño episodes is suddenly on the rise -- and what that might mean.

Christmas Surprise
El Niño, the Spanish term for the Christ child, got its deceptively soothing name decades ago because it tended to show up around Christmas in Peru every three to seven years. It is part of a larger natural pattern, the combined El Niño-Southern Oscillation (ENSO), causing a vast, periodic reversal of conditions in the equatorial Pacific that unsettles weather patterns worldwide.

El Niño's impact is usually greatest in the winter and lasts for several months, though sometimes it can continue into the spring. If this year's El Niño is anything like its predecessors, it will bring the United States: cooler, wetter weather across the entire southern tier, including rain-short Southern California; a warmer, drier winter in the northern tier; more soggy days but fewer hurricanes in the southeast; and uncommonly dry conditions in the mid-Atlantic. ("We're reasonably sure" that the current rainfall deficit locally is an ENSO effect, Leetmaa said.).

In many parts of the world, its effects began this summer. In Indonesia, where drought began weeks ago, one of the world's largest coffee crops is endangered and dry conditions are aggravating fires in some of the planet's last tropical rain forests. In the northern Philippines, farmers reportedly carried images of the infant Jesus into their fields, praying for rain that has been scarce since May.

In Chile, an erstwhile coastal desert suddenly bloomed this year after dozens of inches of rain. In Peru, freak, heavy snowstorms have stranded travelers in the Andes. And for all of northwestern South America, there is almost certainly more to come. (During the 1982-83 episode, many parts of Ecuador and Peru got 100 inches of rainfall in six months, according to the U.S. National Oceanic and Atmospheric Administration. That's nearly three times what the D.C. area gets in a year.)

In parched Australia, where some ranchers reportedly are killing cattle they won't be able to feed, the government estimates that the wheat crop will be 28 percent below normal. In Zimbabwe, experts have been meeting to plan a response to what is expected to be an uncommonly severe drought there and in South Africa. The last ENSO-related dry spell reduced Zimbabwe's economy by 12 percent, according to one estimate.

Silver Linings
Yet for all their celebrated meteorological mayhem, ENSOs always blow good fortune to somebody. In fact, on balance, most of the continental United States usually benefits -- although the salmon population in the Pacific Northwest is suffering because El Niño pushes Pacific mackerel northward, which eat young salmon and compete with adult salmon for food.

For Florida, where El Niño events are credited with reducing the number and severity of hurricanes in the Atlantic, and for most of Dixie, "El Niño is a good dude," according to Florida State's O'Brien. In a science colloquium earlier this year, he described it as "wonderful positive climate happening for the southeast United States," and noted that, according to preliminary studies, it may even suppress tornadoes in a stretch from Indiana to Mississippi where twisters apparently are more frequent when the opposite of El Niño conditions prevail.

California sports fishermen are buoyant as abnormally warm waters flood the west coastal area with exotic species such as barracuda and yellowtail, presaging a bumper year for the $1 billion-per-year industry. Tuna have been spotted around Alaska. A 100-pound marlin, whose species normally prefers northern Mexican waters, was caught for the first time in recorded history off Washington state. All along the coast, surfers are doffing their wet suits. From Minnesota to Maine, climate-savvy householders are hoping for the kind of lower winter fuel bills they saw in 1983. (El Niño events raise average temperatures about 4 degrees.)

And if ranchers are in trouble Down Under, Australian growers of cotton -- a plant well adapted to warm, dry conditions -- are reporting a spectacular season.

No one is sure yet whether this year's El Niño will beat The Big One. In some respects, it is stronger. For example, since the event started in March, the seas got hotter faster this year than ever before. Even hundreds of feet below the surface, water temperatures in the eastern Pacific are now an extraordinary 14 degrees Fahrenheit higher than normal and surface readings are near 84 degrees.

Nonetheless, the Weather Service's Leetmaa said, "We don't think it can get any bigger than '82-83 because the sea-surface temperatures then were about as high as they could get."

"It's a kind of a horse race now" between this year and the 1982 ENSO, said Michael J. McPhaden, director of NOAA's mid-Pacific network of ocean buoy monitors, called TAO. "I don't know if this one's going to win, but it's certainly going to place."

Scientists have only studied ENSOs meticulously for the past 15 years, after the record-busting 1982-83 event took the world by surprise and wasn't even recognized until it was well underway and ravaging weather patterns around the globe.

One of the most sensitive and useful tools to track sea-surface temperatures, wind patterns and moisture content wasn't in place until 1994: NOAA's TAO network of 70 sensor buoys, tethered along the equator, that report hundreds of measurements daily by satellite relay. Add data from free-floating sensors released by ships and imagery from weather satellites, and there are now thousands of detailed readings per day, every day, from the equatorial Pacific. That's how investigators were able to see telltale signs of this year's event as early as last winter.

On-and-Off Pattern
Researchers also have found that, in general, an El Niño events often tend to be followed by their La Niña opposite: a combination of abnormally cold surface water and abnormally high air pressure in the eastern Pacific, last seen in 1996. Although the ENSO phenomenon predates by thousands of years the human carbon dioxide pollution that now threatens to cause global warming by enhancing the "greenhouse" effect, some scientists worry that the frequency and severity of El Niño effects may have begun to change within the past two decades years.

"We've had two 'hundred-year' events separated by only 15 years," said Leetmaa, who cautions that it's far too early to know whether that might simply be a statistical fluke. So far, most climate experts would probably agree with marine physicist Tim Barnett of the Scripps Institution of Oceanography, who told a Sept. 11 House subcommittee hearing that the best models available show that "As you increase [in the atmosphere], you don't see any increase in El Niños."

Others believe that something odd may be going on. Kevin E. Trenberth, director of climate analysis at the National Center for Atmospheric Research, said "If one simply looks at what's been happening in the tropical Pacific during the past 20 years, it's very unusual." Not only did it have "one of the biggest [El Niño's] on record," but also "this peculiar event that lasted from 1990 to 1995 and is either the longest on record, or three separate events in a row."

Trenberth also notes that there have been eight El Niño events but only three La Niña episodes in that period. By comparison, a study from COAPS shows that in the 53 years from 1944 to 1996, there were 27 neutral years, 15 cold or La Niña episodes, and 11 El Niños. If that is something like a "normal" distribution (and it is impossible to know if it is, or even whether a typical pattern exists because the data cover too short a time span), then the past 20 years have had a disproportionate number of El Niño events.

Even a small amount of global warming, Trenberth said, might reinforce ENSO effects, or nudge the cycle so that they "oscillate around a somewhat different average."

Other scientists see the current ENSO as a reversion to an earlier weather pattern. "In 1982, '86 and '91, we found that there was a tendency for the [ENSO] patterns to develop over a large region of the central and eastern Pacific in the latter part of the calendar year, and then to persist considerably -- or all the way -- into the next year," said Stephen E. Zebiak, an ENSO expert at Columbia University's Lamont-Doherty Earth Observatory.

But this year's "is very reminiscent of the evolution of some of the most distant events, such as 1972, which affected coastal South America in its year of development" and went "through its life cycle and decay rather rapidly," he said. Thus it may be "following rather close to the pattern of these older-style events."

An Inexact Science
These are not academic questions. After all, the Weather Service's Leetmaa noted, most of the immigration boom into Sunbelt havens such as Arizona has taken place in the past 20 years. If that turns out to have been an unusually wet period due to frequent El Niño episodes, where will millions of residents get enough water when the climate turns back closer to the norm?

He and other ENSO veterans suspect it may take 10 or 15 more years of careful measurements to get answers to questions of that sort -- if federal funding for the observation systems continues, which is by no means certain. (The House Appropriations Committee has not funded the administration's request for $4.9 million for the Tropical Ocean-Global Atmosphere observing program at NOAA -- one of the world's premier sources of early data on El Niño formation.)

Among other nagging but fundamental questions, said Michael H. Glantz of NCAR, is the critical issue of "when an El Niño locks in. You tell me when, and I'll have 12 or 16 months of useful information to work with."

More research also could lead to better predictions of ENSO effects, which would have a value of $240 million to $323 million per year in U.S. crop savings alone, Department of Agriculture Under Secretary I. Miley Gonzalez told Congress earlier this month. Overall, the cost-benefit ratio of research expenditures to savings in disaster aid and lost crops is at least 10 to 1, and may be as high as 300 to 1, according to various experts.

However, even if El Niño forecasts were 100 percent accurate, they would only account for approximately one-third of the variability in weather patterns for virtually any specific site. The other two-thirds are determined by unique local conditions, together with other climate shifts that occur on annual, biannual and even decade-long schedules. "El Niño forecasts are information to hedge with, not to sell your farm by," said Glantz.

But the major problem governments here and abroad face has far less to do with shortcomings in the forecast system than with getting people to use the information already available. In this country, that could potentially reduce the estimated $1.2 billion the federal government spends each year in supplemental disaster aid. As Michael J. Armstrong, associate director of the Federal Emergency Management Agency, said at the Sept. 11 House hearing, "The solution to reducing future disaster costs is mitigation." Yet there is comparatively little national or regional planning to anticipate ENSO conditions.

Australia is quite advanced in this regard. The Southern Oscillation index (the difference in air pressure in Australia and Tahiti) is sufficiently well studied, writes Neville Nicholls of Australia's Bureau of Meteorology Research Centre, that it can be used to predict yields "even before the crop is planted." Suitable advance warning, he reported at a July colloquium, can result in "significant increase of profit (up to 20 percent) and/or reduction of risk (up to 35 percent)" when farmers adjust their crop management to match the forecasts.

There might also be substantial public-health advantages. Around the world ENSOs are "associated with upsurges of water-borne diseases such as hepatitis, shigella [dysentery], typhoid and cholera," writes Paul Epstein of Harvard's School of Medicine, as well as diseases carried by animals, including malaria, dengue, yellow fever, encephalitis, schistosomiasis, plague and hantavirus.

He suggests the 1993 outbreak of hantavirus -- carried by mice -- may have been encouraged by El Niño-induced rains. "Six-year droughts in the Southwestern U.S. that devastated populations of owls, snakes and other rodent predators were followed by heavy rains in 1993 that increased food sources for rodents," Epstein writes. "In the absence of predators the well-nourished rodents flourished" and communicated the disease to humans.

Given the ample benefits of planning and the fact that it is now possible to flag presumptive ENSO events months before they peak, "the big question is: What are we going to do about it?" said marine physicist Barnett.

© Copyright 1997 The Washington Post Company

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