Satellite Photos Show El Nino May Be Ebbing
The El Nino current dominating the equatorial Pacific Ocean, which climate experts have forecast as one of the century’s largest and potentially most disruptive weather phenomena, may be on the wane, according to new satellite data released by NASA’s Jet Propulsion Laboratory.
In recent weeks, the vast pool of warm water associated with El Nino--which by November had grown to almost twice the size of the United States--has shrunk by at least 10%, falling to a level last observed in early September.
Although scientists with NASA’s Topex / Poseidon satellite project said the decline could be an early sign that El Nino is retreating, they were reluctant to call it conclusive proof that this year’s powerful current is on its way out.
Even if El Nino is waning, they warned, it has already released enough energy into the atmosphere this year to disrupt weather around the world and warrant predictions of an unusually wet, stormy California winter.
“Anybody who thinks El Nino is going away in the next two months is doing wishful thinking,” said JPL research oceanographer Bill Patzert. “This baby is still big.”
The latest glimpse of El Nino comes from a NASA satellite, launched in 1992, that monitors the status of the world’s oceans by measuring how changing temperatures make the sea surface rise or fall.
Part of a little-understood global climate cycle, the El Nino current arises every few years when the prevailing tropical trade winds abate and the surface waters of the equatorial Pacific grow unusually warm. Scientists do not know what causes the effect and only recently have come to appreciate its far-reaching consequences for the world’s weather.
The current has been appearing more frequently since the late 1970s, many experts believe, with a prolonged El Nino episode dominating global weather patterns from 1990 to 1995. The present episode began last winter, and the current has been gathering force ever since.
Based on the most recent data gathered by satellite and a network of ocean sensors last week, oceanographers concluded that this year’s El Nino has just completed a “double-peak” pattern--because the size of the current peaked first in early October and again in early November.
That pattern, they said, is very similar to what was observed during the 1982-83 El Nino, which devastated the coast of California and caused $10 billion in weather-related damage worldwide. If history repeats itself, scientists say, this year’s current can be expected to peter out over the next several weeks.
But this year’s El Nino current has already demonstrated its unique character. It began earlier and has grown stronger than any previously observed, researchers said.
Indeed, this El Nino may simply be pausing, they said, before gathering even greater force to reach a third peak of intensity before finally subsiding next year. No previous El Nino current has behaved that way, though.
“This may be an early sign of its demise,” said Lee-Lueng Fu, chief project scientist for the U.S. / French satellite project. “We cannot be sure. The next two to three weeks is critical. We will keep a close eye to see if we will have a third peak, which would be rather unprecedented.”
JPL researchers said Monday that they would not be surprised if El Nino continued to grow because the trade winds have not yet regained their strength. Not until they do will the current cycle end, they said.
Even then, the pool of warm water generated by this year’s El Nino is so vast that it could take months to diminish completely.
“The key is the wind,” Fu said. “Even if this is the beginning of the decline, it is going to persist through January and February.
“We are not out of the woods by any stretch of the imagination.”
Another unusual element of this El Nino has been its failure to measurably affect global temperatures. A variety of satellite-based sensors show that temperatures have remained unusually cool despite El Nino, according to researchers at the University of Alabama’s earth system science laboratory in Huntsville.
The heat generated by the enormous pool of warm Pacific water is believed to be equivalent to about 100 times the annual total energy from fossil fuels consumed in the United States.
Yet global temperatures have remained below the seasonal norms throughout the fall, said John Christy, an atmosphere expert at the University of Alabama who gathers accurate satellite temperature readings for almost all regions of Earth.
“The warm El Nino signal appears to be muted in the temperature record,” Christy said, based on temperature reports through October. “We would have expected that by this time the global temperature would be above normal.
“The fact that it isn’t is curious,” he said. “If there is more heat going into the atmosphere from the El Nino, something is happening in the atmosphere to release that extra heat.”
