A Guide to the Coming Weirdness of El Niño

Wildfires torched 2 million acres in Australia. A blistering heat wave killed 2,800 in Indonesia. Thailand’s rice crop failed, causing prices to spike 80 percent. An “atmospheric river” flowed over Northern California, making it rain in San Francisco on 27 days in a single month.

These are just a few of the dramatic effects of the El Niño years of 1982–83 and 1997–98, two of the strongest on record, in the Pacific Rim. This year's El Niño, according to the National Oceanic and Atmospheric Administration, could be even stronger, and researchers are finding convincing evidence that global climate change could be a cause.

El Niño is a phenomenon that occurs irregularly in the tropical Pacific Ocean, usually at intervals of between two and seven years. The name means "the boy" or "the little boy" in Spanish; South American fishers who originally recognized the phenomenon named it in reference to Jesus because they noticed changes in the sea around Christmas.

In a normal year, trade winds blow across the tropical Pacific Ocean from the east—Peru to Indonesia. During an El Niño, those winds weaken, reducing the upwelling of cold water off South America, so the surface water stays warm. Storms typically occurring when oceans are warm—hurricanes happen in summer and early fall, remember—then become more prevalent off the coasts of the Americas. Because the winds aren’t carrying the warm waters to the west, bringing storms with them, Indonesia and Australia suffer droughts. With all the energy the abnormally warm water releases into the atmosphere, El Niño can affect weather virtually anywhere on Earth.

Here’s how El Niño looked in the summer of 1997:

(Illustration by Lauren Wade; Data from U.S. Navy)

On July 27, NOAA's Climate Prediction Center forecast an 80 percent chance that El Niño, which had already started to develop, would continue through spring 2016. It also raised its estimate of the likelihood that this year’s El Niño would be even stronger than the one in 1997–98, to 60 percent.

Could this be related to global warming? As 2015 sets records for air temperatures and a powerful El Niño is forecast, scientists are looking into whether climate change is making this year’s El Niño stronger and whether El Niño will be more frequent as we continue pumping climate-trapping gases into the atmosphere.

Here’s what global sea surface temperature anomalies look like this summer:

(Illustration by Lauren Wade; Data from U.S. Navy)

“Global warming is going on and sea temperatures are higher, so when the events that occur with El Niño take place, the consequences are greater,” said climatologist Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colorado. “There is so much variability from one El Niño to the other that it is hard to tell any linear pattern,” Trenberth said, but one thing we do know is global warming is happening, and we know that it and El Niño both warm the ocean. Therefore “when the two reinforce one another, they have a much bigger effect than either of them individually.”

While Trenberth expects, as a result of global warming, more severe effects from El Niños when we get them, Kim Cobb, a climate scientist at the Georgia Institute of Technology, and her colleagues published a paper in Science in 2013 indicating El Niños are getting stronger. And strong El Niños can be expected to occur more frequently, says climate modeler Wenju Cai of the Commonwealth Scientific and Industrial Research Organisation in Australia.

With the warming this year, we have seen a weak monsoon in South Asia; droughts in southern Australia, the Philippines, and Peru; unseasonal snow and rain in the United States; a heat wave in Brazil; and extreme flooding in Japan.

It might just be the perfect storm for a tumultuous winter. Click on the icons in the map below to see some of the strange weather phenomena, and their consequences, previous strong El Niños have brought, and some we have already seen in 2015 and 2016's El Niño.

Additional reporting by Sean Eckhardt and Nicole Mormann