A heat wave in Brazil. (Photo: RAFAEL VIEIRA / AGIF / AGIF VIA AFP)
The weather phenomenon El Nino could make its appearance again later this year and possibly push global temperatures to record levels.
According to the American National Oceanic and Atmospheric Administration (NOAA), there is a 50% to 60% chance that El Nino will develop between July and September.
El Nino, and the cooler weather phenomenon La Niña, are two phases of a natural climate pattern over the Pacific Ocean.
Fishermen in the 19th century used the term El Nino (“the boy” or “the Christ child”) to refer to an unusually warm ocean current that appears along the coast near Christmas. Scientists chose the name La Niña as the opposite of El Nino. Between the two there is also a “neutral” phase.
The Boy
El Nino can weaken the constant winds that blow from east to west across the tropical Pacific, thereby influencing the weather by changing the movement of warm water right across the ocean.
These weakened winds heat the cooler central and eastern parts of the ocean, change rainfall patterns over the equatorial Pacific region, and also affect wind patterns worldwide.
The extra heat at the surface of the ocean releases energy into the atmosphere that temporarily raises global temperatures, which is why El Nino years often rank among the warmest years on record.
“El Nino causes a temporary increase of about 0.1 °C to 0.2 °C in the planet’s average temperature,” Nat Johnson, a meteorologist at NOAA, told AFP.
El Nino occurs every two to six years.
This typically results in drier conditions in Southeast Asia, Australia, southern Africa and northern Brazil and wetter conditions over Africa, the southern US, Peru and Ecuador.
Archive photo (Photo: Tumisu/Pixabay)
Another record year?
The last El Nino occurred from 2023 to 2024 and contributed to 2023 being the second warmest year on record and 2024 being the warmest on record.
Carlo Buontempo, director of the European Union’s Copernicus climate service, said in January that this year could be “another record year” if El Nino appears.
However, Tido Semmler, a climate scientist at Ireland’s national meteorological service, says the biggest impact will only be felt in 2027 if El Nino develops in the second half of this year.
“It takes time for the global atmosphere to respond to El Nino,” he said.
“Even without that, there is a risk that this year could be the hottest year on record due to the continued trend of global warming,” said Semmler.
“The year 2027 runs a greater risk of reaching record temperatures if El Nino develops in the second half of 2026,” he added.
The Girl
The latest La Niña weather phenomenon was relatively weak and fast.
It started in December 2024 and is expected to move to a neutral phase between February and April.
La Niña cools the eastern Pacific Ocean for about one to three years and has the opposite effect of El Nino on the world’s weather patterns.
This brings wetter conditions to parts of Australia, Southeast Asia, India, Southeast Africa and northern Brazil, and drier conditions to parts of South America.
However, La Niña did not prevent 2025 from being the third warmest year on record.
New calculation method
In February, NOAA adopted a new method to determine El Nino and La Niña events.
The old Oceanic Nino Index (ONI) compared the three-month average seawater temperature in a part of the Pacific Ocean with a 30-year average in the same area.
However, because the oceans are rapidly warming, this method may be outdated.
The new method, the Relative Oceanic Niño Index (RONI), compares how warm or cool the East-Central Pacific is to the rest of the tropics.
NOAA says RONI is a “clearer, more reliable way” to monitor El Nino and La Niña.