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Climate researchers revise decades-old definitions as global temperatures surge
Scientists are revising how the world’s most influential climate cycle — El Niño and La Niña — is measured and labelled, as global warming pushes ocean temperatures beyond the limits of traditional forecasting methods.
For decades, meteorologists used a relatively simple benchmark: when sea surface temperatures in a key region of the equatorial Pacific rose 0.5°C above average, the event was classified as El Niño; when they fell below that threshold, it was labelled La Niña. But in a warming world, what counts as “average” has been rapidly shifting. As a result, scientists now say the old method is increasingly unreliable.
To address this, the U.S. National Oceanic and Atmospheric Administration (NOAA) has introduced a new measurement system that compares Pacific temperatures to the wider tropical ocean rather than a fixed historical baseline. The change aims to better reflect how the atmosphere and oceans interact in a climate already altered by human-driven warming.
The revision signals a broader reality: climate systems that scientists have studied for generations are now behaving differently.
The Climate Engine Behind Global Weather
El Niño and La Niña are phases of the El Niño–Southern Oscillation (ENSO), a natural climate cycle that shifts temperatures across the equatorial Pacific Ocean every two to seven years. These fluctuations influence weather patterns worldwide.
During an El Niño, warmer Pacific waters can drive hotter global temperatures, alter rainfall patterns, and disrupt agricultural seasons. Regions such as South America often see increased rainfall, while areas including Australia and Southeast Asia can experience drought.
La Niña, by contrast, brings cooler Pacific waters and often produces the opposite effects — including stronger hurricanes in the Atlantic and wetter conditions in parts of Asia and Australia.
Together, these phases act as a powerful regulator of global weather, influencing everything from monsoon intensity to wildfire risk.
A Mysterious Temperature Spike
The changes to ENSO classification come after scientists observed an unexpected jump in global temperatures between 2023 and 2025, above the already rising trend caused by greenhouse gas emissions.
Research suggests that part of the explanation lies in a rare “triple-dip” La Niña event that persisted from 2020 to 2023. During this prolonged phase, cooler surface waters effectively trapped heat within the Earth system.
When the cycle shifted toward El Niño conditions, much of that stored energy was released into the atmosphere — similar to removing the lid from a pressure cooker.
Scientists estimate that roughly three-quarters of the recent increase in Earth’s energy imbalance can be attributed to the combination of long-term human-caused warming and the transition from La Niña to El Niño.
Other possible contributors to the temperature spike include reduced pollution from shipping, increased solar output, and the effects of underwater volcanic eruptions — though greenhouse gas emissions remain the dominant driver.
Why “Normal” No Longer Works
For more than 75 years, ENSO classifications relied on comparing ocean temperatures to a 30-year historical average. However, as global oceans steadily warm, that baseline has become outdated.
Scientists first attempted to adjust the system by updating the baseline every decade. Later, they shortened the update period to five years. But even that proved insufficient as warming accelerated.
The newly adopted relative oceanic index instead measures Pacific temperatures against the broader tropical ocean. In practice, this means future climate records may report more La Niña events and fewer El Niño events, even if the physical processes remain similar.
The goal is not to redefine the climate cycle itself, but to ensure that the classification accurately reflects how atmospheric patterns respond to ocean conditions.
What It Means for the Future
Climate forecasters are already watching the Pacific closely. Some projections indicate a significant chance of El Niño conditions emerging later in 2026, which could push global temperatures even higher in the following year.
If that occurs, 2027 could challenge or exceed current global temperature records.
Scientists caution that while El Niño and La Niña are natural cycles, their impacts are now unfolding in a warmer climate system loaded with excess heat.
That combination can amplify extreme weather events — including heatwaves, droughts, floods, and powerful storms.
As one climate researcher warned in response to the new findings, the message is simple: the climate system is entering unfamiliar territory, and societies should prepare for increasingly volatile conditions.
References
- Euronews – Scientists change El Niño labelling to keep up with temperature spike
https://www.euronews.com/2026/02/23/everyone-should-buckle-up-scientists-change-el-nino-labelling-to-keep-up-with-temperature- - Associated Press / AP News – Scientists change how El Niño is labeled to keep up with spike in temperature
https://apnews.com/article/e3499ef5e1081604770c4cf5f95910b3 - NOAA Climate Prediction Center – ENSO Monitoring and Oceanic Niño Index
https://www.cpc.ncep.noaa.gov - The Guardian – Chance of El Niño could push global temperatures to record highs
https://www.theguardian.com/environment/2026/feb/08/global-weather-el-nino-pacific-ocean-high-temperatures-2027 - San Francisco Chronicle – New rules change how La Niña and El Niño are classified
https://www.sfchronicle.com/weather/article/el-nino-la-nina-noaa-21316733.php
