UK Met Office has warned that a developing El Niño over the Pacific Ocean could become the strongest in living memory, with the powerful climate phenomenon likely to drive global temperatures higher and make 2027 the hottest year on record.
According to scientists, the event is already showing exceptional strength, with sea surface temperatures in a key region of the Pacific more than 2C above average. Forecasts indicate the anomaly could exceed 3C later this year as El Niño approaches its expected peak, potentially making it an unprecedented event in records dating back to 1950.
Prof Adam Scaife, Head of Long-range Forecasting at the UK Met Office, stated that the intensity of the signal emerging in current forecasts was unlike anything he had previously observed.
“We should be clear that this is an unprecedented event. I have never seen an El Niño signal this intense in our forecasts.”
Prof Adam Scaife
The warning comes as scientists monitor increasingly unusual conditions across the Pacific and assess how the phenomenon could affect weather patterns across continents. El Niño is a naturally occurring climate pattern that develops every two to seven years and generally lasts for about a year, but its effects can extend well beyond the Pacific Ocean.
The phenomenon develops when the trade winds that normally move from east to west across the tropical Pacific weaken or reverse. This allows unusually warm water to shift eastwards, releasing large amounts of heat from the ocean into the atmosphere and altering atmospheric circulation.
Scientists classify an El Niño event when sea surface temperatures in a key Pacific region are at least 0.5C above average. Current readings are already substantially beyond that threshold, while some forecasts suggest the anomaly could climb above 3C.
The potential strength of the event is raising particular concern because large quantities of unusually warm water have accumulated below the surface. Temperatures at depths of around 100 metres have been recorded at about 8C above normal in some areas, providing what scientists describe as a reservoir of heat that could reinforce the developing phenomenon.
According to Dr Zeke Hausfather, a Climate Scientist at Berkeley Earth, the continuing development of the event is increasing confidence that it could eventually set records.
“We have many months to go while this event continues to develop and that’s one of the reasons that we have increased confidence that this will be a record-setting event.”
Dr Zeke Hausfather
Other climate groups have projected that Pacific temperatures could rise even further, potentially reaching 4C above average. Hausfather noted that if such projections materialised, the event could rank among the strongest El Niño episodes experienced over several centuries, although scientists acknowledge that reliable observations do not extend far enough into the past to establish such a comparison with certainty.
The developing El Niño is already being watched for signs of its influence on weather patterns around the world. Its effects vary from one event to another, but historically it has been associated with drought, flooding, altered monsoon patterns and changes in tropical storm activity.
In South Asia, the 2026 southwest monsoon has been running below average, raising concerns in a region where millions of people depend on seasonal rainfall for agriculture and water supplies.
El Niño can also influence hurricane activity in the Atlantic by changing wind patterns across the Caribbean and tropical Atlantic. The current season has so far recorded only three named storms, although scientists caution that multiple factors influence tropical cyclone development.
The effects may be more severe elsewhere. In Australia, El Niño can make drought and bushfires more likely, whereas in regions of Peru, Ecuador, and the southern United States, it can make flooding more likely.
The consequences go beyond the actual weather. Temperature and rainfall variations can harm infrastructure, interfere with agriculture, decrease water availability, and put more strain on food systems and vulnerable communities.
The United Nations Food and Agriculture Organization issued a warning earlier this month that El Niño could put tens of millions of people in vulnerable nations at risk of severe food shortages.
The concern is particularly significant because the developing event is emerging against a backdrop of human-induced climate change. The planet is already substantially warmer than it was before large-scale industrialisation, meaning natural climate variations such as El Niño now operate against a much warmer baseline.
That combination could make the consequences of the current event more severe than those associated with similar El Niño episodes in the past.
El Niño Raises Fears of Wetter, Stormier UK Autumn
While El Niño is not considered a major driver of the record-breaking heatwaves experienced in the UK during the current summer, the Met Office expects the phenomenon to have a greater influence on weather patterns during autumn and early winter.
According to the Met Office, El Niño can increase the likelihood of wetter and stormier conditions across north-west Europe, including the UK.
The relationship between El Niño and British weather is not straightforward, however. The phenomenon is only one of several factors influencing the UK’s climate, and scientists stress that it cannot be used to predict individual storms or rainfall events with certainty.
El Niño can also be associated with colder conditions later in winter, although that relationship is less consistent.
Its potentially greater global significance lies in its influence on average temperatures.
During a strong El Niño, large quantities of heat are transferred from the ocean into the atmosphere. The resulting increase in global temperatures can become particularly pronounced in the calendar year following the winter peak of the event.
According to Met Office Climate Scientist Dr Nick Dunstone, the release of ocean heat during El Niño could result in a significant increase in global average temperatures in the following year.
“Hence, 2027 is very likely to replace 2024 as the warmest year on record,” he added.
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