APPNDX SAT 2

This is an appendix to: The Saturation Chronicles - 25

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From: Can We Blame El Niño?

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Misconceptions about El Niño

Since its discovery, people have been trying to understand and explain ENSO by generalizing its effects or connecting it to all extreme weather events. As a result, people may hold some ideas about El Niño that aren't necessarily true. The following brief discussions can clear up some common misconceptions about El Niño.

Misconception #1: All the impacts of El Niño are negative.

Fires in southeast Asia, droughts in eastern Australia, and flooding in Peru often accompany El Niño events. Much of the media coverage on El Niño has focused on the more extreme and negative consequences typically associated with the phenomenon. To be sure, the impacts can wreak havoc in developing and developed countries alike, but El Niño events are also associated with reduced frequency of Atlantic hurricanes, warmer winter temperatures (and reduced heating costs) across the northern United States, and plentiful spring/summer rainfall in southeastern Brazil, central Argentina and Uruguay, which leads to above-average yields from summer crops.

Misconception #2: El Niño periods cause more disasters than normal periods.

On a worldwide basis, this isn't necessarily the case. In some regions, we've seen that El Niño exerts fairly consistent influences on climate. For example, El Niño conditions typically cause more rain to fall in Peru, and less rain to fall in Indonesia and Southern Africa. Combined with socioeconomic factors, these conditions can make a country or region more vulnerable to adverse impacts.

However, compared with normal conditions, characteristic El Niño patterns enable climate scientists to produce more accurate seasonal forecasts and better predictions of extreme drought or rainfall for several regions around the globe. In turn, this improved predictability can help societies be better prepared to avoid or reduce potentially negative impacts. Ultimately, with better predictions, fewer areas with increased vulnerability may develop as disasters.

Misconception #3: El Niño and La Niña significantly affect the climate in most regions of the globe.

Actually, El Niño and La Niña significantly affect only about 25% of the world's land surface during any particular season, and less than 50% of land during the entire time that ENSO conditions persist.

Misconception #4: Regions that are affected by El Niño and La Niña see impacts during the entire 8 to 12 months that the climate conditions lasts.

Most regions experience impacts only during one specific season, and this can be months after the ENSO conditions first develop. For example, the recently developed 2009 El Niño may cause the southern U.S. to get wetter-than-normal conditions from December to March, but Kenyans may see wetter-than-normal conditions between October and December.

Misconception #5: We should worry more during El Niño episodes than La Niña episodes.

Not necessarily. Each set of conditions come with their own features and risks. In general, El Niño is associated with an increased likelihood of drought across tropical land areas, whereas La Niña is associated with an increased risk of drought in the mid latitudes.

Misconception #6: The stronger the El Niño/La Niña, the stronger the impacts, and vice versa.

Not necessarily. The important point to remember is that ENSO shifts the odds of some regions receiving more or less rainfall than they usually do, but it doesn't guarantee that this will happen. For example, scientists expected the very strong El Niño of 1997/98-which triggered wildfires in Indonesia and flooding and crop loss in Kenya-might also result in below-normal summer rainfall in India and South Africa, but this didn't happen. On the other hand, India experienced strong rainfall deficiencies in 2002, during a much weaker El Niño.

Also, there are other large-scale climate oscillations at work in the global climate system. Sometimes when these other oscillations-such as the Pacifical Decadal Oscillation or the North Atlantic Oscillation-are happening at one of their peak phases, their effects can dampen or even completely offset the effects from an ENSO event.

Misconception #7: El Niño and La Niña events are directly responsible for specific storms or other weather events.

Just as we can't blame any particular hurricane on global climate change, we can't confidently pin a single weather event on an El Niño or La Niña. ENSO conditions typically affect the frequency or strength of weather events. What we can say from climate records is that over the course of a season with El Niño or La Niña conditions in place, some regions experience more or less rainfall than average.

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