Emory Report

February 2, 1998

 Volume 50, No. 19

First Person

Is there an El Niño in your
future or just a bad hair day?

There is a phenomenon afoot, and you'd have to have been locked in a closet the past six months not to have noticed. Actually there are two phenomena: the physical one we call El Niño and the media blizzard it has spawned. The two are not necessarily related nor is it clear which is the more dangerous.

The physical El Niño is, among other things, a warming of the waters of the equatorial eastern Pacific Ocean. It has been blamed for an astounding variety of events from last summer's catastrophic floods in eastern Europe to the prolonged dry season in Indonesia to, no doubt, the Braves' failure to win the National League Championship. The warming is one phase of an irregular cycling of events along the equatorial realm known as the El Niño-Southern Oscillation (ENSO). The ENSO acronym illustrates our present understanding that the phenomenon is both oceanographic (El Niño) and atmospheric (Southern Oscillation) in origin and effect.

The opposite end of the cycle, when the eastern Pacific is unusually cold, is called La Nina. It too has a list of global climate effects. As complex as ENSO is, we now understand it well enough to be able to predict confidently the onset of the warm phase and give reasonable warning to those regions likely to feel its effects.

The media blitz surrounding El Niño is far more difficult to predict and has significantly broader and longer-lasting consequences. As a general rule, scientists know they're in over their heads when their research specialty becomes the subject of a Dave Barry column and is summarily explained away as a combination of espresso machines and whale snot. This is not quite what our science mavens had in mind when they directed us to spread the gospel of science's role in the human condition, but it had to happen.

El Niño has become a buzzword in the buzzword center of the universe. It's short, rather catchy as buzzwords go and exotic. Exotic is especially important when it comes to laying blame-America's new pastime. In the world of weather it's as good a scapegoat was we're likely to get, short of the impact of an asteroid the size of Macon-but that's a separate report. Even though there is some correlation between the El Niño of Barry's column and this year's weather, the recent blame is only partially deserved.

Climatologists base El Niño correlations, known as teleconnections, on statistics, painting their forecasts in terms of seasonal probabilities. The general public doesn't understand probabilities, choosing either to ignore or to misinterpret probability-based phenomena. Do you, for instance, really know what a forecast calling for "a 60 percent chance of rain" means? Does anybody really know what a 60 percent chance of rain means?

Actual government forecasts of expected El Niño effects on Atlanta-area weather might say, "Mid-latitude low pressure systems tend to be more vigorous than normal in the Gulf of Mexico and along the southeast coast of the United States, resulting in wetter than normal conditions in that region." This forecast covers the winter months of December, January and February. This is not quite the same as "Run inside, Helen, there's an El Niño coming up the street!"

Here's the problem: it rained all yesterday, is worse today and the forecast calls for two more days of rain. Is this an El Niño storm? No. Will climatologists attribute the winter precipitation total, higher in part due to this storm, to El Niño? Yes. There's an important distinction to be made between weather and climate as well as between direct and indirect effects.

Weather is what it's like when you step outside; climate is what it's been like in recent history, usually 30 consecutive years. One day's storm gets blurred into seasonal norms.

El Niño's tropical effects are significantly different than its effects outside the tropics. Because we live outside the tropics, all El Niño teleconnections are indirect effects: the weather system moves pools of warm water in the tropics, which moves pools of water outside the tropics, which affects the speed, shape, and location of the polar and subtropical jet streams, which alters the surface storms that bring our winter precipitation.

Within the tropics the effects are more direct. Thus Indonesia's prolonged drought is a direct effect of El Niño, as is the storm that floods the coastal desert of Peru, which typically gets a cupful of rain in a good year. And if Peru can have an El Niño storm, then why can't the greatest nation in the world, for goodness sakes? In a way, we're seeing the effects of our over-efficient news system, which can show the floods in Somalia and the haze in Indonesia as they occur. Modern telecommunications have effectively eliminated time as a news factor and, in doing so, have removed distances as well. If it can happen there, why can't it happen here?

Few Americans seem to know enough physical geography to understand how weather and climate vary across the globe and through the seasons. So we wind up blaming climate effects for specific disasters and mixing tropical causes with extra-tropical events.

The situation boils down to an exercise in communication. The physical scientist predicts a wetter, more turbulent winter, and the public sees a disaster coming up the street. The communication is there-and I believe the broadcast and print media do a good job informing the public-but, understandably, there are different perceptions of what is being communicated.

This is based partly on a general lack of understanding of our physical world and partly on our human tendency to prefer the specific to the general. Few people, for example, can warm up to a forecast of an 80 percent probability of a 35 percent increase in winter precipitation over the norm. It's far more satisfying to blame the storm that just ruined your best umbrella and soaked your socks on that alien interloper El Niño and convince yourself that somehow Peru is behind it all.

Nevertheless, the misconceptions and fun we're having with El Niño this winter are similar to the difficulties before us as we begin to face up to the onus of potential global warming. Back to you, Dave.

Woody Hickcox is senior lecturer in geosciences. For more information about weather and climate conditions, he suggests visiting the Climate Diagnostics Center web site at <http://www.cdc.noaa.gov/ENSO/>.

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