El Niño is here. And prepare for a bumpy ride, scientists say: By the end of 2026, it could become the strongest El Niño on record.
On June 11, the U.S. National Oceanic and Atmospheric Administration confirmed that Earth had officially entered the “warm” El Niño phase of an approximately two- to seven-year-old ocean-climate pattern known as the El Niño Southern Oscillation, or ENSO.
El Niño events affect weather patterns globally – and the stronger they are, the more disruptive they can be to human health, agriculture and infrastructure. Forecasters currently predict that there is a 63% chance that by winter this event will become a “very strong” El Niño, sometimes called a “super El Niño.”
Here are three things to know as this weather pattern takes hold.
What is an El Niño?
The El Niño phase of ENSO (unlike a neutral phase or La Niña) is characterized by months of warmer-than-normal sea surface temperatures in the eastern equatorial Pacific. Peruvian fishermen in the 1600s noticed this warming that often occurred around Christmas time and dubbed the phenomenon “El Niño,” meaning “little boy” or “baby Jesus” in Spanish.
“Southern Oscillation” refers to a shift between areas of high atmospheric pressure and low atmospheric pressure over the eastern Pacific Ocean and the western Pacific Ocean. This shift triggers changes in atmospheric circulation, air temperature and precipitation on a global scale.
Scientists track these air pressure changes at two main weather stations: in Darwin, Australia (to the west) and Tahiti, in French Polynesia (to the east). During neutral and La Niña phases, the high pressure area is to the east, so the prevailing winds blow westward across the equatorial Pacific Ocean. Winds push warm surface waters of the Pacific westward, away from the coasts of the Americas, allowing cold, nutrient-rich water to well up from the ocean depths. This keeps the waters of the eastern equatorial Pacific cold.
But every few years there is a reversal, with high pressure over the western Pacific and lower pressure over the eastern Pacific. This weakens or even reverses the direction of prevailing winds, allowing warm surface waters to stay in place – and effectively suppressing upwelling of cold water. Sea surface temperatures are warming rapidly in the eastern Pacific, signaling the start of an El Niño phase.
According to Tom Di Liberto, a climate scientist with the Washington, D.C.-based nonprofit Climate Central, no two El Niño events are the same. But what they all have in common is that they transfer a huge amount of heat from the tropical Pacific into the atmosphere. And this heat blast can significantly increase global temperatures during the event.
What would make this year’s event “great”?
An El Niño phase officially begins when sea surface temperatures in the eastern equatorial Pacific Ocean remain at least 0.5 degrees Celsius above average for several months. The warmer the waters, the stronger the impacts are likely to be. Waters 2 degrees Celsius warmer above average signal the start of a very strong, or “super,” El Niño.
Since April, researchers have observed consistently above-average temperatures in the eastern equatorial Pacific Ocean, and dozens of forecasts around the world predict an impending El Niño. By June, as the ocean continued to warm, these forecasts began predicting it would be a major event.
Climate change has made it more difficult to detect temperature anomalies that signal the onset and intensity of an El Niño phenomenon, due to uneven warming from one region to another. So in May, NOAA’s Climate Prediction Center adopted a new tool for its El Niño forecasts, called the Relative Ocean Niño Index, which adjusts for warming linked to climate change.
Using this new measurement, NOAA predicts that this winter, sea surface temperatures in the eastern tropical Pacific will likely be 63 percent warmer than 2 degrees Celsius above average this winter, signaling the start of a super El Niño.
Climate simulations predict “incredibly high” global temperatures for November and December, Di Liberto says. Such heat can have deadly consequences, not only because heat-related illnesses, but also increase in pest-borne diseases such as cholera, typhoid and malaria.
In addition to increasing global temperatures, El Niño changes the position of the Pacific jet stream, meaning some areas become drier, while others become wetter. For the United States, one of the biggest impacts is from tropical cyclones: While El Niño years can generally mean more and more intense cyclones in the Pacific, changes in wind patterns can hinder the formation of hurricanes in the Atlantic.
That said, the life cycle of an El Niño is relatively short: events typically form in summer, strengthen in winter, then die out in spring.
How will this year compare to past powerful El Niños?
The most recent El Niño episodes occurred in 2015-2016, 1997-1998 and 1982-1983.
The 1997-1998 event was the largest on record. This increased the average global temperature for that period 1.5 degrees Celsiusand led to devastating extreme weather events. These include torrential rains and flooding in Peru and East Africa, which in turn sparked an outbreak of Rift Valley Fever in the region; droughts that sparked deadly wildfires in Southeast Asia; powerful storms that caused catastrophic flooding and landslides in California. Rising ocean temperatures have caused the bleaching of about 16 percent of the world’s coral reefs.
Such strong El Niño events leave a long mark on the global economy, researchers reported in 2023 in Science. Global economic losses attributed to the 1997-1998 event are estimated at around $5.7 trillion. The 1982-1983 event cost the world an estimated $4.1 billion.
It is not yet certain whether this year’s event will reach super status. But because this event occurs on top of an already rapid warming of global temperatures due to human-caused climate change, its impacts will likely be dramatic, even if the event proves only moderately strong, Di Liberto says. “It wouldn’t take a very strong El Niño to see records broken this year. »
