When you hear about El Niño, perhaps you first think of Chris Farley. Or maybe you lived in Southern California in 1997, so you remember the storms, floods, and mudslides. If you’re a scientist, you might think of that remote section of the equatorial Pacific where higher-than-normal sea surface temperatures define El Niño and influence climate and weather around the globe. Or (just maybe!) you think of my El Niño article from the spring (check it out for more background on the science of El Niño).
But you may not know of the myriad other impacts El Niño can have around the world. Some of them can actually be positive, like better growing conditions for agriculture in Uruguay. But many are negative, and some are less directly obvious. Drought and food insecurity in Cambodia. Rift valley fever in Somalia. Fishery collapse in Peru. Malaria transmission in Colombia, eastern Africa, and other areas.
So how does El Niño exert this broad influence? Some refer to El Niño as a storm, but that’s not quite accurate. The conditions of the ocean and atmosphere in the equatorial Pacific operate on a natural cycle, known as El Niño Southern Oscillation (ENSO). When the cycle swings to one extreme or the other—i.e., sea surface temperatures being much cooler (La Niña) or warmer (El Niño) than normal—it can set in motion a series of cascading atmospheric effects. There are typical patterns of this cascade, which do tend to lead to more storms in some places (like the west coast of South America and Southern California), but also to less rainfall in other places (like Indonesia and Australia). Temperature patterns are similarly affected.
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While many of the El Niño impacts may seem bleak, the silver lining is scientists’ ability to predict them, which gives time for governments and organizations to prepare. Take the malaria example, for instance. Malaria is transmitted to humans via mosquitoes of the genus Anopheles. These mosquitoes are highly “climate-sensitive”—meaning they’re evolved for well-defined temperature, rainfall, and humidity ranges. El Niño can change the ranges of these climate variables in an area, such that conditions may be more or less optimal for mosquitoes. In parts of eastern Africa, for example, the increased precipitation associated with El Niño has directly corresponded with large outbreaks of malaria. While this is not good news, the fact that we know this means actions can be taken, such as extra prevention measures.
Madeleine Thomson works at the intersection of climate and health at the International Research Institute for Climate and Society at Columbia University (disclaimer: I also work there). In addition to the benefit of having time to take action before rains come, she also sees another opportunity. "El Nino acts as a test to see if we’re ready to manage the risks of more extreme climate,” Thomson said. “This is particularly true with malaria. There have been these big declines in malaria over recent years. Can those declines be held down when we have an El Niño, which by all indications looks like it’s going to increase rainfall across eastern Africa?”
Since experts predict that climate change will increase the number of extreme climate events, Thomson added that such a test serves as an indication of our vulnerability to climate change. It’s an opportunity to see if societies can organize to protect themselves from climate risk, she said.
Marc Levy, a political scientist at Columbia University, is also watching the El Niño event closely. As the deputy director of the Center for International Earth Science Information Network, Levy’s research includes environmental security and the dynamics between natural and human systems. While climate scientists predict that this El Niño could be comparable to the 1997-98 event—the strongest since at least 1950—Levy is thinking about how El Niño’s impacts this year will compare to that event. “Whatever social impacts unfold will be a function of today’s patterns of vulnerability and resilience," said Levy. “And the world has changed a lot since 1997-98.”
On the one hand, we have better knowledge of El Niño, with better ability to predict both weather and downstream risks. But there are also changes that have increased our vulnerability, he said.
“In 1997 there were about 5.9 billion people in the world. Today it is 7.3 billion, and that growth has been concentrated in countries that have weak abilities to cope with climate stress,” said Levy. “Real food prices are about 65-70 percent higher today than they were in 1997-98, meaning that shocks to food prices triggered by crop production problems will create greater hardship on societies than before. And, as a result of globalization and changes in government policy, our global grain reserves have shrunk by about 35 percent since 1997-98, making it harder to respond quickly to a large global food crisis.”
So what about impacts in the U.S.? In general, the further from the tropical Pacific, the less influence El Niño has on a region’s climate. Mike Halpert, deputy director of the National Ocean and Atmospheric Administration’s Climate Prediction Center, says that historically the strongest signal of El Niño influence on U.S. climate is for a wetter-than-average winter in the southeastern part of the country, especially the Gulf Coast. Halpert is hesitant to make any statements about the Northeastern U.S., but says if it does turn out to be one of those rare, very strong El Niños, there’s elevated chance for a milder winter.
Halpert cautioned, however, that we have only observed a few strong El Niño events, so experts don’t have much data with which to base predictions. “I know a lot of folks are looking at California because of the drought,” said Halpert. “But the signal isn’t as strong there as it is in the Southeast. From my experience, when you think you have something like this figured it out, you’re thrown a curve ball and learn you don’t have it all figured out.”
