Are your ideas about El Niño and La Niña primarily influenced by Chris Farley’s 1990s “Saturday Night Live” sketches?The late comedian’s definitions were funny, if a bit lacking in scientific precision. (Meaning of “Niño” in Spanish)
There is now much more interest in the tropical Pacific climate patterns, and they are even more complex than SNL described.
El Niño occurs when ocean temperatures in the tropical Pacific Ocean rise far above average. Because this area is much warmer than the surrounding water, the atmosphere reacts and weather patterns change. That’s why we care so much about El Niño and its cooler sister, La Niña.
The old method of detecting this was known as the oceanic Niño index. Scientists compared ocean temperatures in a specific region of the tropical Pacific Ocean, known as the Niño 3.4 region, with other regions of the tropical Pacific Ocean. The greater this difference, the greater the El Niño phenomenon.
However, global warming has made this method difficult. The rapid warming of the entire tropical Pacific Ocean is masking El Niño-related anomalies. If the oceans heat up everywhere, El Niño becomes harder to see.
So scientists switched to a new way to measure El Niño and La Niña: RONI (Relative Ocean Niño Index). The new method involves a simple but effective mathematical trick. Scientists subtract the temperature anomalies in the rest of the tropical Pacific Ocean from the temperature anomalies in the region that are most important for El Niño.
The new method essentially removes climate change from the entire equation, making El Niño easier to spot. Scientists will be able to see it sooner and long-term weather forecasts will also improve.
It is critical that scientists accurately predict and detect El Niño and La Niña events. That’s because El Niño and La Niña events can change weather patterns even thousands of miles away, causing flooding in some areas and drought in others, causing billions in damages. It also impacts the Atlantic hurricane season.
To better understand what this new index means and how it works, I reached out to two of the most knowledgeable scientists in the field: Michel La Roux of the National Oceanic and Atmospheric Administration and researcher Emily Becker of the University of Miami.
Le Roux, who leads NOAA’s El Niño and La Niña forecasts, said the new index “better captures ocean-atmosphere interactions across the tropical Pacific.” Older methods are “increasingly capturing changes in the ocean that are not reflected in upper-level atmospheric circulation.”
El Niño and La Niña are known as linked phenomena, meaning that changes in the ocean are reflected in changes in weather patterns in the atmosphere.
“Coupling means that changes in things like wind and rainfall need to move in sync with changes that are occurring at sea level,” says Rollou.
Leroux said traditional methods are gradually losing sight of El Niño due to background warming occurring across the Pacific Ocean. “The old index was like looking at the tropical Pacific Ocean through blurry glasses, but now I’ve upgraded to new prescription glasses and can see El Niño/La Niña more clearly,” she said.
Becker pointed to human-induced climate change as the cause of the blurred vision.
“What we found is that over the past decade or so, the strength of El Niño and La Niña events, as measured by the traditional Niño index of 3.4, has become out of sync with the pattern of influence that we were seeing,” Becker said. “Through our research, we discovered that the Earth’s oceans are warming so rapidly that our traditional measures are warming them too fast.”
He said the new index better captures the intensity of these events and their impact on weather patterns, while subtracting the effects of changing climate baselines.
In other words, we can now more accurately detect the “Niño event” in Farley’s sketches, taken at the height of the massive El Niño event of 1997-1998, and predict its effects more clearly.
