All Signs Point to El Niño

Global weather patterns may be changing this year.

Since March, ocean temperatures have rapidly increased in a short period of time, suggesting that the climate pattern known as La Niña was on her way out. Last month, the National Oceanic and Atmospheric Administration announced it was now on the lookout for the opposite climate shift—El Niño. The watch was established because “conditions are favorable for the development of El Nino within the next six months,” the agency wrote. Here’s what that means.

What is El Niño and how does affect North America? 

El Niño is when the “ocean temperatures are warmer and precipitation is greater than normal in the area spanning the central to eastern Pacific Ocean,” according to NOAA. The name means “the boy” or “little boy,” and the phenomenon is named after el niño dios, which is what many Latin Americans call baby Jesus. The change in temperature was first noticed in South America around Christmas time, which is why the shift is named after the religious figure.

El Niño’s sister, La Niña (“the girl”) is the opposite shift, where ocean temperatures are cooler than average. Both of these can last as short as several months, but either can also stick around for several years. La Niña recently hung around for about three years before officially leaving. The warming of the ocean during El Niño years changes some global weather patterns. Tt causes the Pacific jet stream to move south, bringing more rain to the U.S. East Coast and higher temperatures in northern climates. Another sign that El Niño conditions are forming are changes in the wind.

“We have what are called the trade winds, which blow from east to west, through most of the tropics,” Aaron Levine, a research scientist at the University of Washington, told Earther. “What we’re looking for is a weakening of those trade winds.” During this time, parts of Canada and the Northern U.S. tend to be warmer and drier than average. Meanwhile, areas along the bottom half of the U.S. see more precipitation and higher chances of flooding.

According to Levine, the Western U.S. could see a milder wildfire season, which often peaks in the summer. And though it’s warmer during this time period, there is a likelihood of more precipitation for a lot of the country. But this isn’t a hard rule. “The winter of 2015-16, which was a fairly large El Niño event, was not actually a wet year in California,” Levine noted.

A map of how El Niño can affect North America.Image: NOAA

Marine animals are also affected by El Niño. Upwellings that bring nutrient-rich water from deeper in the ocean closer to the surface are less likely to occur. This means that there are fewer phytoplankton off the Pacific Coast and fewer fish that eat the phytoplankton.

How does El Niño affect hurricane season?

During recent La Niña years, there was a more active Atlantic hurricane season. During El Niño, the hurricane season shifts away from the Atlantic. “It increases activity in the eastern Pacific basin, but tends to decrease to less than normal activity across the Atlantic basin,” Jon Gottschalck, chief of the operational prediction branch at NOAA’s Climate Prediction Center, told Earther.

This means that the East Coast may see fewer hurricanes from the Atlantic Ocean and the Caribbean, while the Gulf Coast and the Pacific will see an uptick in tropical storms. During El Niño, storms form and get closer to islands off the West Coast, including the Hawaiian islands. There are other factors that have affected the summer to fall hurricane season, too, like rising global temperatures connected to climate change.

“We know in a general sense by studying previous events over the last 50 years, or longer, about what the typical impacts are,” Gottschalck said. “We’re constantly trying to learn more information on the physical drivers of how El Niño develops.”

Is El Niño responsible for recent ocean temperature spikes?

According to Gottschalck, the recent spikes in ocean temperatures can’t yet be pinned to a potential formation of El Niño. Experts are keeping an eye out for all of the conditions, so we’re not officially in one yet. Though ocean temperatures have risen this year, trade winds are still going strong. This means that the warming from the ocean has not spread, which is why El Niño has not been officially declared, Reuters reported.

“Those impacts may come in during the late fall, winter, and help spur on generally a warmer year overall,” Gottschalck said. “There is some time for the atmosphere to respond to the changes in the ocean. There’s a lag there. So it’s not instantaneous.”

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