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Most of the snow was precipitation that usually falls somewhere over the western Pacific, perhaps in Indonesia or Australia. But in 1997, for reasons scientists still don't understand, Pacific trade winds slackened --a telltale signature of El Niño-- and the weather came our way instead. My problems were small compared to South Americans who lost entire villages to El Niño-driven floods, but I was still passionate when I hoped El Niño would leave and not return. Above: The question on every dog's lips is "When is the snow coming back?" Recently, their sledding season has been cut short thanks to the influence of La Niña. Be careful what you wish for, they say, it might come true. Indeed, El Niño didn't return after 1998. But what came next, La Niña, was in its own way just as bad -- only longer-lasting. "La Nina conditions developed soon after the '97-98 El Niño," says Bill Patzert, an oceanographer at NASA's Jet Propulsion Laboratory. "That's normal. Big El Niños are always followed by a few years of La Niña -- an extreme anti-El Niño weather pattern."
Above: Dams like this one on the Sacramento River in northern California generate hydroelectric power and account for roughly 20 percent of the state's electricity. During dry years there's less hydro-power to go around. Image courtesy of the U.S. Bureau of Reclamation. "Droughts aren't caused entirely by La Niña," cautions Patzert. "Other factors, like the human impact on farmland, are important too. But La Niña does contribute." Even California's energy crisis is due, in part, to La Niña conditions. Hotter-than-average weather means more air conditioners running full blast, while dry conditions reduce stores of hydroelectric power.
Although few of us long for the stormy perils of 1997, there are some Californians who feel that a nice wet El Niño --perhaps just a modest one-- wouldn't be such a bad thing.
Right: Dry conditions lead to wildfires. Image credit: John McColgan (Bureau of Land Management, Alaska Fire Service) and the Alaskan Type I Incident Management Team. What's holding El Niño at bay? "It could be the Pacific Decadal Oscillation," Patzert says. The Pacific Decadal Oscillation, or "PDO" for short, is a widespread pattern of sea-surface temperatures in the Pacific Ocean that cycles back and forth between two opposite phases every 10 to 20 years (for comparison, El Niño-La Niña appear every 2 to 7 years). In the "negative" phase of the PDO cycle cooler surface waters in the eastern part of the Pacific are surrounded by warmer waters in the north, west and south. (The positive phase is just the opposite.) Negative PDOs appear in sea surface temperature maps as a "horseshoe" of warm water surrounding a cooler "wedge."
Left: This June 7, 2001, sea surface elevation map from the U.S.-French TOPEX/Poseidon satellite reveals a wedge of cool (blue/purple) water in the Eastern Pacific is surrounded by a vast horseshoe of warmer water to the north, west, and south. [more] It seems that "negative PDOs can also act as El Niño repellents," says Patzert. In the 1950's, 60's, and 70's, decades characterized by a negative PDO, El Niños were less frequent and weaker. In the 1980's and 90's, when the PDO was positive, strong El Niños happened more often. If history is a reliable guide --and this is still controversial, cautions Patzert-- the ongoing negative PDO could increase our wait for a new El Niño and weaken it when it does arrive.
The coming years and decades will be an exciting time for researchers as they monitor the PDO and its shorter-lived cousins El Niño and La Niña. "We're just beginning to learn all the rhythms of the Pacific," says Patzert, "and how they mold weather across the globe. Satellite measurements of these patterns are critical to improve our climate models and forecasts." Meanwhile, there's a yard full of sled dogs in California who couldn't care less about climate models, but they sure would enjoy some snow and they're willing to live through another El Niño to get it. It seems they'll have to wait at least another year -- bad news for sledding, perhaps, but a welcome respite from snow shoveling! Editor's note: It's tempting to think of El Niño and La Niña -- both extreme weather patterns -- as bad. After all, they can trigger floods and fires, wash away villages, and even contribute to the energy shortage! But that's not the whole story. "For example," notes Patzert, "the El Niño winter of '97-98 was so mild in the northern United States that the price of oil dropped because of lower demand for heating oil. El Niños also suppress destructive Atlantic and Gulf hurricanes. And west coast surfers love El Niño because it brings waves and warm water." Good or bad? It all depends on your perspective. |
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June
28, 2001 -- During the winter of 1997 and '98, I learned
to really dislike El Niño. At my mountain home in California
it wouldn't stop snowing. I spent several hours a day shoveling
the stuff, mainly out of my dog yard, the home of a dozen Siberian
Huskies. Whenever the snow level reached about five feet they
could jump the fence en masse and wreak havoc around the
neighborhood. So rather than dog sledding, which is what we usually
did when it snowed, I shoveled.
In 1997,
El Niño pulled North America's 
Alas, the 
USA
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