September 20, 2023 — The Pacific Ocean is a juggernaut. It’s the largest ocean on our planet, almost double the size of the Atlantic. Its vast expanse, exposure to trade winds, and range of temperatures makes it incredibly dynamic. All these factors contribute to create the El Niño—Southern Oscillation (ENSO), a climate pattern that affects seasonal precipitation, heat, storms, and more around the world.
ENSO is made up of three stages: El Niño and La Niña, which can both increase the likelihood of extreme weather from the Philippines to Hawaii to Peru—and the neutral phase that we are typically in. El Niño is currently underway and is predicted to go strong until winter. With it come a slew of weather patterns like exacerbated heat waves in the northern US and Canada, increased risk of flooding in the south and southeast US, delayed rainy seasons, and even droughts in countries like Indonesia and the Philippines. And this is for an El Niño period that is predicted to be strong, but not particularly extreme. But as the Pacific warms due to human-driven climate change and temperature gradients across the ocean widen, scientists warn that El Niño and La Niña periods are becoming longer, more extreme, and more frequent.
In one recent study published in the journal Nature Reviews, researchers looked at different climate models to see how ENSO has changed through the past century, and how it may shift in coming years. While El Niño and La Niña ordinarily last nine to 12 months, the vast majority of models predict that we will see them stretch out over multiple years. “In the 20th century you got about one extreme El Niño per 20 years,” says Wenju Cai, chief research scientist at the Commonwealth Scientific and Industrial Research Organisation in Australia and lead author of the Nature Reviews paper. “But in the future, and in the 21st century on average, we will get something like one extreme event per 10 years—so it’s doubling.”