Balmy temperatures in New England, drought in the Caribbean, flooding rains in California that are responsible for at least 14 deaths and $2 billion in damage—the world of weather this winter has turned upside down. What gives? Climate experts say much of the blame falls on a seemingly innocuous Pacific Ocean weather pattern known as El Niño.
"The effects of El Niño can be both exciting and deadly, "says Tim Barnett, a research marine physicist at Scripps Institution of Oceanography in Lajolla, Calif, and a foremost authority on the sporadic condition. But Barnett, 56, who lives in La Jolla with his wife, Judie, 55, a high school English teacher, cautions that the phenomenon is only beginning to be understood. He spoke with correspondent Kurt Pitzer.
What is El Niño?
El Niño is a large-scale change in the global climate that occurs when a permanent pool of warm water near Indonesia begins spreading eastward, warming the surface of the Pacific along the equator all the way to Peru and Ecuador. Typically, El Niños happen every two to seven years and last about a year.
What causes them?
They begin to form when Pacific trade winds weaken, allowing a large water mass to move eastward along the equator. Changes in the ocean temperature can in turn affect the winds. There's a circular effect.
How much do the temperatures change in the affected parts of the ocean?
Not much. You might see a difference of several degrees—maybe from about 82° to 86° Fahrenheit—though the difference can be as much as 10 degrees off the coast of South America.
How can El Niño affect temperatures in New England?
El Niño causes atmospheric changes. It displaces the subtropical jet stream flowing four miles above the ocean, so the storm patterns that follow the jet stream get moved either north or south of their normal path. This year it put a storm track over New Mexico, Arizona and California, which may have helped increase rainfall in those states.
So there are other forces involved?
Yes, we're discovering other powerful climate creatures at work. For example, we recently discovered a 20-year cycle—originating in the North Pacific—in which colder, wetter weather alternates with warmer, dryer weather over large regions of North America. But how factors like this interrelate with El Niño is unclear.
How about the floods in The Netherlands?
The El Niño effect is very hard to find there. The atmosphere is a very chaotic, noisy place. By the time you get to Europe, it's hard to find weather changes related to El Niño.
Where did El Niño get its name?
Its effects, periods of heavy rains and floods, were noted in the old log books of the missions of Peru and Ecuador in the 1500s. In the 19th century Peruvian fishermen, noticing that the ocean tended to get warmer at Christmas time, termed the phenomenon El Niño, the Christ child. Scientists adopted the name to describe the stronger periodic warming of the waters. Before then it was called the Painter, because as the water gets warmer in the shallow bays and estuaries, plankton die and turn the bottoms of the boats black.
Do the equatorial waters ever get cooler instead of warmer?
Yes, the phenomenon has two personalities: warm and cold. A cold one is called La Niña, and everything sort of happens in reverse. We had one in the summer of 1988; some studies suggest it was responsible for the drought in the Midwest, with barges high and dry on the Mississippi River.
Are El Niños surfacing more frequently?
It's not clear, but we have seen a swarm of them during the past 15 years. They've occurred in the winters of 1982-83, 1986-87, 1987-88, 1991-92 and this year. The worst one was in 1982-83. There were devastating floods in Peru and fires in Australia from lack of rain. This year's El Niño is relatively mild.
Does the frequency have anything to do with global warming?
Some scientists suggest there may be a connection, but there have been other times in history where this sort of frequency occurred. It's sort of controversial right now.
Does El Niño ever have any benefits?
Generally not, because it generates weather that wasn't planned for. But there are isolated exceptions. If you like to sportfish off Southern California, you get an incredible run of tuna coming in El Niño years, when the ocean temperatures rise to those of the tuna-rich waters off Mexico.
What would happen if there were no El Niños?
The weather would probably be a heck of a lot more routine. You wouldn't have the wilder extremes of colder and wetter winters. It would certainly be less exciting.
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