Dispatches from the La Niña Summit
(Dispatch #2)
Mary K. Miller
July 16, 1998
Boulder, CO.

Many people have the impression that scientists are lone wolves, toiling away in the lab or field until they wrestle a problem to the ground and emerge with an answer. There's an element of truth to that, but the last two days of the La Niña Summit show that there's another side to science. The 100 or so men and women who constitute most of the world's leading experts on El Niño/La Niña came to NCAR this week to exchange information and ideas, probe, challenge, and sometimes yell at each other. Yesterday, I heard one researcher roar at another who questioned his methods; a few hours later they were chatting over a cup of coffee. The goal of all the debates is consensus, agreement by most of the scientific community on a set of principles. Consensus doesn't necessarily mean the scientists are right, just that they're more likely to be right--until new information or ideas change the picture. And sometimes the consensus is simply that we don't know enough yet.


Some of Michael Glantz's goals in organizing the conference were for scientists to reach consensus on what La Niña is, what should be communicated about it to the public, and what we can expect from the weather this winter. It doesn't look like the experts agree on those answers yet, but they're closing in. One of the difficulties of predicting the weather and climate is that it's always changing and no two years are the same.

Michael Glantz, a social scientist at NCAR (and Milton Berle's nephew) organized the La Niña Summit.


Scientists recognized a developing La Niña last spring when a pool of cool water starting spreading into the eastern tropical Pacific. From past La Niña events, they can offer pretty good odds that the Indian subcontinent, Southeast Asia, and Australia will have heavy or above-normal rains this year, and that the northern U.S. will have a cold, snowy winter, while the Southwest will have a warmer, drier winter. But like every El Niño, every La Niña is different. Scientists never know from statistics exactly how tropical ocean temperatures, winds, and pressure gradients create changing global weather patterns.

To help them figure out the causes and effects of weather and climate, many researchers turn to computer climate models. Computer models, also called coupled or dynamical models, are the lab rats of the climatology profession. They allow researchers to perform multiple controlled experiments with a simulated climate--something they can't do with the real world.

The CIRES computer model--developed by Marty Hoerling and others at NOAA, the University of Colorado, and other universities across the county--is state of the art. The computer code in the CIRES model reconstructs the complex and dynamic interactions that drive our often chaotic climate, especially the relationship between the ocean and atmosphere. The model predicts changes in temperature, wind speed and direction, ocean currents, clouds, rain, heat transfer, and atmospheric pressure patterns--all the factors that help create weather and climate on earth. Those model results are compared with observations from actual climates to ensure that the models are realistic.



Marty Hoerling, a climate modeler from the University of Colorado, is working to tease out the weather impacts of La Nina.

 


So far, as we heard at the La Niña Summit yesterday from Tony Barston, a researcher at the Climate Prediction Center, the dynamical models aren't doing a smashing job at predicting the magnitude or timing of La Niña and El Niño events or their apparent effects on long-range weather patterns. He evaluated models from six different research groups and only one came close to duplicating the last El Niño. "The models have a long way to go," Dr. Barston said, and added that it will probably be another 10-15 years before the models do better than looking at statistics from the past. But even though the models aren't perfect, Barston encouraged researchers to stick their necks out, make predictions, and learn from errors to make the long-range climate models better.

 

 

One meteorologist who did stick his neck out (and incidentally lost his job later) was Joe Friday, former head of the National Weather Service (NWS). During the height of El Niño last winter, he ran experiments with the weather models used by NWS to forecast the national weather. He ran the model with El Nio conditions plugged in, and compared the results with model runs that didn't include El Niño. When he ran the model with El Niño, it duplicated an ice storm that struck the northeastern U.S. last February. Without El Niño conditions, the model didn't produce an ice storm. It was the first time a researcher definitively tied a specific weather event with El Niño. Of course, the scientists at the La Niña Summit hasten to add that not all ice storms can be pinned on El Niño. Joe Friday's results are very controversial, so maybe even last February's ice storm can't be blamed on El Niño. Still, it's possible that some day, in a few years or a few decades, scientists and their computer models will provide more reliable and specific information on when El Niño and La Niña will appear, and how these tropical Pacific conditions affect weather across the globe.

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