Climate scientists are monitoring growing signals that an El Niño climate pattern could form in the Pacific Ocean later this year, an event which some researchers say could push global temperatures to an all-time record high in 2027.
The development centres on the El Niño Southern Oscillation (ENSO), a cycle of ocean temperatures in the Pacific that is linked to extreme weather events worldwide. An El Niño occurs when warmer-than-average waters gather in the eastern equatorial Pacific, a phenomenon that tends to give global average temperatures a boost.
Both the US government’s National Oceanic and Atmospheric Administration (NOAA) and Australia’s Bureau of Meteorology have noted that some climate models are forecasting an El Niño. However, both agencies have cautioned that these results come with significant uncertainties.
In its latest southern hemisphere outlook, Australia’s bureau stated: “Some models suggest the possibility of El Niño development from June.” It described this as a “very long lead time” for such a prediction. NOAA has similarly pointed to “growing chances of El Niño” while highlighting model uncertainty.
Experts stress it is currently too early to be confident. Dr Andrew Watkins, a climate scientist at Monash University and former head of long-range forecasts at the Australian bureau, said the “precursors are there” but it remained unclear if one would fully develop. He explained that a large store of warm water in the western tropical Pacific could, if trade winds ease, move eastward and warm waters off South America—a typical precursor seen in models for the coming autumn.
Associate Professor Andrea Taschetto, an ENSO expert at the University of New South Wales, said the current La Niña phase—where warmer waters are closer to Australia—is ending. Forecasting beyond that is difficult, she said, with the chances of an El Niño developing, or conditions being neutral, in the June to August period currently about “50/50 or like tossing a coin”.
The potential climate impact is a key focus. Research scientist Dr Zeke Hausfather of Berkeley Earth said an El Niño that formed in mid-2023 likely added about 0.12C to global temperatures in 2024. Should a new one develop later this year, he projects it would peak around November to January and “primarily impact 2027 global surface temperatures, rather than 2026.” He has predicted that 2027 will likely set a new record for global temperature if a moderate to strong El Niño event develops.
Dr Watkins agreed that an El Niño would more strongly impact 2027 temperatures, stating he “would be hesitant to bet against a hottest year on record.” He added that the underlying global heating from fossil fuel burning is now “so strong” it is “simply overtaking year-to-year variability,” meaning a strong El Niño might not even be necessary to produce record warm years. This comes after the past three years each ranked among the top three warmest on record for the planet, as published by The Guardian.
