The Dallas Morning News - 7/22/2002

Health/Science

El Niño tiptoes back in

Weak new cycle may make Texas winter a bit wetter, cooler

07/22/2002

By ALEXANDRA WITZE / The Dallas Morning News

Last time El Niño showed up, it was climate's enfant terrible. This year it's

behaving more like an enfant pacifique.The newborn El Niño in the Pacific

Ocean seems much quieter than the screaming version that arrived five

years ago. The 1997-98 El Niño caused at least $32 billion in damage

through droughts, floods, wildfires and other natural disasters worldwide.

The 2002 El Niño may not cost a penny.

Still, even a quiet child conceals secrets. And scientists are using this

summer to coax out the secrets of El Niño.

This year's El Niño won't affect weather in the United States until fall,

scientists say. They're using that time to ponder why they haven't made

much progress since 1997 in forecasting the onset of El Niños.

Says El Niño researcher Mark Cane, "I

would have to count the level of progress

as somewhat disappointing. ... Certainly

there have been no great

breakthroughs."

There is some promising news. Although forecasters can't predict exactly

when an El Niño might appear, once it arrives they can track its growth

and forecast its effects better than ever. Researchers also better

understand the many climate factors, from wind patterns to ocean

currents, that can transform a slight warming of the Pacific Ocean into a

full-fledged, planet-altering phenomenon.

Fishermen working off South America were the first to recognize El Niño

about a century ago as the presence of unusually warm water in the

eastern Pacific. They named it "the little boy" in Spanish, in reference to

the Christ child, because the phenomenon tended to show up around

Christmas.

In recent years, scientists have targeted El Niño with a new fleet of

weather satellites, ocean buoys and ship voyages to track slight

temperature changes in the Pacific. Other researchers develop

sophisticated computer models to try to predict the onset of El Niños.

This year, El Niño forecasting has been more on target than in 1997. But

that owes more to the weakness of this El Niño, scientists say, than to

skill on the part of computer models.

Without any dramatic changes in ocean temperature to really test this

year's El Niño forecasts, "it's been a sort of frustrating experience," says

Lisa Goddard, a climate forecaster at the International Research Institute

for Climate Prediction.

Early this year, the ocean waters in the eastern equatorial Pacific began

warming just slightly more than usual – typically a sign of an approaching

El Niño. In late May and early June, the warming picked up speed.

This month, the National Oceanic and Atmospheric Administration

announced that the ocean temperatures were toasty enough to qualify as

a true El Niño event. Sea surface temperatures in a designated swath of

the Pacific had been measured at 0.5 degrees Celsius (0.9 degrees

Fahrenheit) above normal for three months in a row.

That meets NOAA's definition of an El Niño, but other researchers aren't

yet ready to give the warming a label.

"I call it an incipient El Niño," says oceanographer Michael McPhaden of

NOAA's Pacific Marine Environmental Laboratory in Seattle. "We're at the

beginning of something that, if it continues along this path, will eventually

turn into an El Niño."

To Dr. McPhaden, an El Niño requires warmer-than-normal temperatures

for five, not three, months straight.

Rather than quibble about definitions, forecasters are busy trying to track

the warming and improve their computer models.

This year's warming barely compares with that of 1997-98, the event "that

made El Niño a household name all over the world," says Dr. McPhaden. By

this time in summer 1997, sea surface temperatures in the eastern

equatorial Pacific were 3 to 4 degrees Celsius (roughly 5 to 7 degrees

Fahrenheit) warmer than normal.

Heat stored in the upper layers of the ocean is a major force driving

Earth's climate. The extra heat of an El Niño can alter wind and ocean

currents, creating weird weather events worldwide. The 1997-98 event

was one of the most powerful ever seen – perhaps even bigger than the

monster El Niño of 1982-83, which caused $13 billion in damage.

Still, in 1997, forecasters missed how early and how hard the El Niño

would begin. That may be because, among other factors, forecasters

didn't yet appreciate the role of westerly winds in the western Pacific, says

Dr. Goddard.

Many climate ingredients came together in 1997 to prime the ocean for a

massive El Niño, she explains. Early that year strong westerly winds blew

across the Pacific, sending warm water eastward toward South America.

The winds blew strongly enough, at just the right time, to pump the

eastern equatorial Pacific full of heat.

"Once you tweak the system hard enough, it kind of gets you into a point

of no return for El Niño," she says. "We haven't seen that level of

disturbance this year."

Today, the heat content in the same region of the Pacific is less than half

what it was during the summer of 1997, says Dr. McPhaden. And a puny El

Niño means puny effects on everyday weather.

In Texas, the presence of an El Niño generally means that winters will be

cooler and wetter than normal, says Benjamin Giese of Texas A&M

University.

"It's part of a change that occurs all the way from California through

Florida, where the southern-tier states experience colder and wetter

winters," he says.

Accordingly, NOAA's seasonal outlook for Texas calls for a

wetter-than-normal fall 2002 through spring 2003.

But don't blame El Niño for bad weather this summer, such as the recent

flooding in Central Texas, Dr. Giese says. El Niño's effects typically show up

first in the Southern Hemisphere – such as in Ecuador, which experienced

record flooding in March – and move into the Northern Hemisphere by fall

or winter.

By next summer, forecasters should know whether their models worked

better than in 1997. There are dozens of computer models that try to

simulate El Niño conditions; only about four of them are sophisticated

enough to link the effects of wind and water together, making those

models the most accurate.

Scientists have offered various explanations for what failed in 1997 – such

as flaws in the data or gaps in information about certain regions of the

world such as the Indian Ocean. And with fixes, some of the models

appeared to work better in hindsight on the 1997 event.

But forecasters may never make that breakthrough that allows them to

see an El Niño coming months in advance, says Vernon Kousky of NOAA's

Climate Prediction Center in Camp Springs, Md.

"These things are like weather phenomena," he says. "You can't really

anticipate them – it's like trying to forecast the weather a month in

advance."

As one example, Dr. Kousky points to the westerly wind bursts that primed

the ocean for an El Niño in 1997. Figuring out why these westerly wind

bursts occur every 30 to 60 days, and what effect they have on Pacific

warming, is one frontier for El Niño research.

Another is studying a longer-period phenomenon, a climate factor known

as the Pacific Decadal Oscillation.

Like El Niño, which oscillates into a cold phase (known as La Niña) and

then back to warm every four to five years, the Pacific Decadal Oscillation

fluctuates between cold and warm about every 50 years. Some

researchers speculate, without much data, that this oscillation may be on

the verge of switching from warm to cold.

If so, that might mean that El Niños could be weaker and come less

frequently than they have during the past 25 years, says Dr. Giese of

Texas A&M.

And this year's weak El Niño might just be a harbinger of the future.

For more on El Niño, visit www.elnino.noaa.gov.

E-mail awitze@dallasnews.com

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