Scientists change how El Nino is labelled to keep up with temperature spikes

The natural El Nino cycle, which warps weather worldwide, is both adding to and shaped by a warming world, meteorologists said.

A new study calculated that an unusual recent twist in the warming and cooling cycle that includes El Nino and its counterpart La Nina can help explain the scientific mystery of why earth’s already rising temperature spiked to a new level over the past three years.

Separately, scientists have had to update how they label El Nino and La Nina because of rapid weather changes caused by global warming. Increasingly hot waters globally have caused the U.S. National Oceanic and Atmospheric Administration this month to alter how it calculates when the weather pattern has flipped into a new cycle. It’s likely to mean that more events will be considered La Nina and fewer qualify as an El Nino for warming tropical waters.

Earth’s average monthly temperature took a noticeable jump up from the long-term upward trend connected to human-caused climate change in early 2023, and that increase continued through 2025. Scientists have many theories about what’s happening, including faster global warming, less pollution from ships, an underwater eruption, and increased solar output.

In a new study in Nature Geoscience this month, Japanese researchers looked at how the difference in energy coming to and leaving the planet — called earth’s energy imbalance — increased in 2022. An increased imbalance, or more trapped heat, then leads to warmer temperatures, scientists said. The researchers calculated that about three-quarters of the change in earth’s energy imbalance can be attributed to the combination of long-term human-caused climate change and a shift from a three-year cooling La Nina cycle to a warm El Nino one.

El Nino is a cyclical and natural warming of patches of the equatorial Pacific that then alters the world’s weather patterns, while La Nina is marked by cooler than average waters. In turn El Ninos tend to increase global temperatures and La Ninas depress the long-term rise.

From 2020 to 2023, earth had an unusual “triple dip” La Nina without an El Nino in between. In a La Nina, warm water sticks to a deeper depth, resulting in a cooler surface. And that reduces how much energy goes out into space, said study co-author Yu Kosaka, a climate scientist at the University of Tokyo.

She compared it to what happens when people have fevers: “If our body’s temperature is high then it tends to emit its energy out, and the earth has the same situation happening. And as the temperatures increase, it acts to emit more energy outward. And for three-year La Nina, it’s the opposite.”

About 23% of the energy imbalance driving the recent higher temperatures comes from this unusually long La Nina pattern, with slightly more than half coming from gases from the burning of coal, oil and gas, the study authors said. The rest can be other factors.

Scientist Jennifer Francis of the Woodwell Climate Research Center, which wasn’t involved in the study, said the research makes sense and explains an increase in energy imbalance that some scientists were attributing to accelerated warming.