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  February 1998    

South America's unruly child
Every few years, an El Niño causes the world's weather to go haywire. The name - Spanish for "The Child," referring to the baby Jesus - was originally given to the warm current that comes to the coast of Peru and Ecuador every Christmas. Now, the term is reserved for the exceptionally warm and long-lived currents that arrive every two to seven years, beginning in the summer and lasting as long as 18 months.

According to Michael Glantz, a senior scientist at the National Center for Atmospheric Research, Boulder, Colorado, until 1982 the world had ignored El Niņo's gentle balm at its peril. Dr. Glantz was the guest speaker at a UNU Public Forum on 12 November titled "Usable Science: El Niño Forecasts in the Service of Society." He told the audience that El Niño phenomena have a big impact on the weather not only locally but around the world as well.

"Some places get floods and storms; some get droughts. The effects of El Niño can be devastating," he warned. The strongest El Niño this century, which peaked in the winter of 1982-83, is estimated to have caused at least $12 billion-worth of damage.

Dr. Glantz recounted that the 1982-83 El Niño caught the attention of the world's scientists and that since then scientists have pretty much figured out what goes on during an El Niño. He pointed out that the Pacific Ocean normally is fanned by the constant breath of the trade winds - east-to-west breezes that push warm surface water away from the ocean's eastern side (off Peru and Chile) and allow cold water to well up from the depths in its place. He said that under normal conditions the surface water builds up in the west, around Australia and the Philippines, making the water several degrees warmer and a meter or so higher than on the eastern side of the ocean. But he said that if the winds slacken, warm water begins to slosh back across the ocean, while the upwelling in the east slows down.

"The effect is somewhat like tilting a bathtub so that there is more water at one end and then straightening it so that the water sloshes back," Dr. Glantz explained.

The end result is like shifting the western Pacific Ocean and its weather systems 6,000 km eastward, while holding the rest of the world still. When the Pacific's warm water moves east, so does the rain, leaving previously wet areas like Indonesia, the Philippines and northern Australia in drought. Conversely, the western edge of South America, off which the ocean is normally too cold to trigger much rain, gets a soaking.

This is just the beginning. Dr. Glantz said that through ever more complicated twists, an El Niño's odd effects are propagated across the world's weather systems. A change in the weather patterns over Africa causes the Middle East to get some welcome extra rain during El Niño winters but creates droughts in places like Zimbabwe and India. Weather systems that develop in the Caribbean are less likely to turn into hurricanes. And so on.

Dr. Glantz told the audience that predicting El Niños can help people take advantage of their good effects as well as reduce their bad ones. But though the effects of El Niños are now becoming clearer, he acknowledged that what triggers them still remains mysterious.

Dr. Glantz announced that the UNU is planning a project called "El Niño and the Pacific Rim Countries" to help make El Niño less of a mystery. "We want to make people more aware of El Niño's impact and to conduct a lot more training on how its effects can be mitigated," he said. Dr. Glantz is hopeful that the UNU's project might create an El Niño early warning system. This would be a major accomplishment. Unfortunately, any early warning system will never remove all uncertainties: El Niños will likely always produce unforshadowed changes. However, the UNU's project is sure to improve decision-making.

Decision makers need more than just predictions about whether an El Niño will occur. They need reliable information about El Niño's social impacts that they can use. For example, knowing how an El Niño will affect people living in dry parts of Papua New Guinea will help authorities choose which crops to plant in order to avoid hunger, or such information may help motivate governments in wet countries where mosquitoes flourish to launch nationwide inoculation programmes. An El Niño-related storm cannot be stopped, but a famine or a severe outbreak of malaria just might.

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