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According to the U.S. National Oceanic and Atmospheric Administration (NOAA), there is a 50–60 percent chance that El Niño will develop between July and September and continue beyond that period. At the same time, NOAA expects the transition from La Niña to a neutral ENSO state to occur between February and April, with a probability of around 60 percent.
However, NOAA warns that model uncertainty remains “considerable.” Forecasts made this early in the year are often less accurate.
What are El Niño and La Niña?
El Niño and La Niña are two opposing climate phenomena in the Pacific Ocean that influence weather patterns around the world. Normally, trade winds blow from east to west across the Pacific, pushing warm surface water toward the western Pacific.
- El Niño (Spanish for “the boy”) occurs when these winds weaken or reverse. Warm water then accumulates in the eastern Pacific, raising sea surface temperatures above normal.
- La Niña is the opposite: the trade winds strengthen, pushing warm water further west toward Australia and Southeast Asia. Cold deep water rises along the coasts of North and South America (a process called upwelling), cooling the sea surface there—especially along the Americas.
El Niño events occur irregularly, roughly every two to seven years, and typically last about a year, sometimes longer. They are often followed by a La Niña phase.
How does El Niño affect global weather?
“El Niño usually suppresses rainfall across large parts of tropical land areas,” says Kieran Hunt, a climate scientist at the UK’s National Centre for Atmospheric Science.
This often means:
- Drier monsoon seasons in Asia, Africa, and South America
- Increased rainfall and occasional flooding in the southern United States, Peru, Argentina, southern Europe, Kenya, and Uganda
- Stronger heatwaves in tropical regions
Because of these effects, El Niño years are often among the warmest on record. Many meteorologists estimate that a typical El Niño temporarily raises the global average temperature by about 0.1 to 0.2°C.
This effect is still much smaller than human‑driven climate change, which has already warmed the planet by about 1.0 to 1.5°C since pre‑industrial times.
A new way to define El Niño
For 75 years, meteorologists classified El Niño and La Niña based on temperature deviations in three tropical Pacific regions compared to long‑term averages.
- El Niño: sea surface temperatures 0.5°C above normal
- La Niña: 0.5°C below normal
These “normal” values were based on 30‑year averages.
But as greenhouse gases continue to heat the planet, what counts as “normal” is shifting.
NOAA therefore introduced a new index last month. Instead of comparing Pacific temperatures only to historical Pacific averages, it compares them to temperatures across the entire tropical belt.
Recently, differences between the old and new methods have reached up to 0.5°C. “That’s enough to matter,” says Nat Johnson, a meteorologist at NOAA’s Geophysical Fluid Dynamics Laboratory.
The new system will likely classify more La Niña and fewer El Niño events than before, Johnson adds.
What this means for the future
“If El Niño develops, we will likely see a new global temperature record,” says Jennifer Francis of the Woodwell Climate Research Center.
“‘Normal’ has been behind us for decades. With this much heat in the system, everyone should be prepared for more extreme weather.”
- Hector Pascua with reports from de.euronews.com/picture: pixabay.com
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