The term “El Nino” has dominated headlines in recent weeks as much of the world struggles to cope with extreme weather.
US meteorologists announced the return of the phenomenon earlier this summer, warning it could contribute to record global temperatures and the hottest year ever recorded in 2027.
Here the Independent examines what El Nino is, how it interacts with human-driven climate change, and how it is currently affecting weather conditions across the UK.
What is El Nino?
El Nino – which means “little boy” in Spanish – is widely used to describe the warming of sea surface temperatures in the tropical Pacific Ocean that occurs every few years.
The phenomenon typically takes place every two to seven years and lasts several months.
It disrupts weather patterns worldwide and pushes up global temperatures.
The name comes from South American fishermen centuries ago, who noticed warmer-than-normal coastal conditions periodically around Christmas time and nicknamed it “El Nino” in reference to the birth of Jesus.
What is La Nina?
Scientists discovered an opposite weather pattern to El Nino in the 1980s and named it La Nina – meaning “little girl” in Spanish.
This natural climate pattern sees surface water in the tropical Pacific Ocean become unusually cool and can last for up to three years.
When did the current El Nino begin?
US meteorologists from the National Oceanic and Atmospheric Administration (NOAA) announced the beginning of El Nino in June, saying it could last until spring 2027.
The previous El Nino event lasted around 12 months from June 2023 and May 2024.
It followed the world’s most recent La Nina event, which lasted roughly 31 months from late 2020 to early 2023.
What usually happens during El Nino?
That part of the Pacific where El Nino happens can shift weather patterns across the globe and cause a range of impacts depending on its strength.
These include the risk of heavy rainfall, storms, floods and droughts in certain locations around the world, as well as soaring temperatures.
The extreme weather can devastate crop yields and ecosystems, drive health crises and cause major economic damage.
The last El Nino intensified global heat, drove severe droughts, heavy floods, widespread marine heatwaves and coral bleaching across the world.
It also contributed to 2024 being the hottest year on record globally.
How is this El Nino event different?
Many forecasts suggest that this El Nino will end up being the strongest on record.
Although not a scientific term, media outlets and commentators are calling it a “super El Nino”, which is when sea surface temperatures rise at least 2C above the long-term average.
Last week, NOAA confirmed that temperatures had exceeded this threshold and said El Nino is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere autumn and winter 2026-27.
The agency said that during the October-December 2026 season, there is a 69% chance of a historic event that would exceed the strength of El Nino events dating back to 1950.
Professor Adam Scaife, head of long-range forecasting at the Met Office, said: “A typical El Nino leads to an equatorial Pacific sea-surface temperature rise of between one to 2C, with 2C being a really big event.
“This implies that if the forecast is accurate – and other forecast systems show similar extreme values – then 2026 will far exceed our recent experience of El Nino and its worldwide climate influences.”
Why could 2027 be the hottest year on record?
Forecasters say this unprecedented El Nino means next year could be the hottest on record.
Dr Nick Dunstone, Met Office science fellow, said: “During large El Nino events significantly more heat is released from the ocean to the atmosphere, leading to an increase in global average temperature, particularly in the calendar year following the winter peak of the El Nino.
“Hence, 2027 is very likely to replace 2024 as the warmest year on record and be another year to temporarily exceed plus 1.5C above the pre-industrial period”.
How is climate change involved?
The relationship between climate change and El Nino events remains an area of scientific research.
Some research suggests that global warming can contribute to making El Nino events more intense.
Burning fossil fuels for energy and transport drives climate change by trapping more and more of the sun’s heat in the atmosphere.
This is leading to cascading effects such as melting ice sheets, warming oceans, biodiversity loss and volatile weather conditions.
As El Nino adds extra heat to an already-warming planet, the effects of one activity can compound the impacts of the other.
“If climate heating is loading the dice towards more extreme events, then El Niño is adding weight,” she said.
How could it affect the UK?
Forecasters have warned that the UK is set to experience more storms and rain in autumn and winter caused by the “unprecedented” El Nino event.
Professor Adam Scaife said: “We should be clear that this is an unprecedented event.
“I have never seen an El Nino signal this intense in our forecasts.”
It comes after the UK experienced a string of heatwaves and shortage of rainfall over the summer, which created the driest July in 190 years and has pushed almost three-quarters (71.3%) of England and all of Wales into drought.
This has put severe pressure on the water system, wildlife, farmers, emergency services and infrastructure.
Professor Stephen Belcher, the Met Office’s chief of science and technology, said: “This summer we have experienced heat waves across Europe reminding us of the effects of climate change, this large El Nino is a reminder that natural variations in the climate system are also at play, adding to the stresses of climate change.”