El Niño breaks Pacific temperature record as exceptional weather pattern intensifies

The Pacific Ocean's most closely watched temperature zone just broke its own record, and the weather system driving it hasn't even peaked yet. In September, sea surface temperatures in the Nino3.4 region—a stretch of tropical Pacific water that meteorologists use as an early warning system—climbed to 29.70 degrees Celsius, according to the EU's Copernicus Climate Change Service. That number matters because it surpasses the warmest readings from three of the strongest El Niño events on record: the episodes of 1982-1983, 1997-1998, and 2015-2016. The current pattern is still intensifying, and forecasters have been predicting for months that it could become the strongest El Niño ever documented.

El Niño is the warm phase of a natural climate cycle that plays out across the Pacific every two to seven years, typically lasting nine to twelve months. When it takes hold, it raises sea temperatures across the tropical Pacific and reshapes weather patterns globally—shifting winds, pressure systems, and rainfall in ways that can trigger droughts in some regions and floods in others. The phenomenon also amplifies the warming already underway from human-caused climate change. This particular El Niño is arriving at a moment when the planet is already running hot.

September's global ocean temperatures tell that story. Average sea surface temperatures worldwide hit 21.05 degrees Celsius last month, breaking the previous September record of 20.92 degrees set just three years earlier in 2023. On land and sea combined, September ranked as the world's second hottest on record, with average surface air temperatures reaching 16.27 degrees Celsius. That puts the planet 1.63 degrees above the baseline scientists use to measure warming—the pre-industrial average from 1850 to 1900. The numbers are climbing faster than many expected.

There is some technical debate about whether this El Niño is truly the strongest ever recorded. Copernicus cautioned that it cannot yet make that claim definitively, partly because climate change itself has warmed the tropical oceans, making recent events appear stronger than historical ones when using raw temperature comparisons. The service has adopted a new index that accounts for this baseline warming, and by that measure, the current event has not yet surpassed past episodes. Japan's weather agency, however, declared on Friday that El Niño conditions had reached their strongest intensity on record, with temperatures running 4 degrees Celsius above normal in the monitoring area. Different forecasters use different scales, and the picture remains somewhat unsettled—but the consensus is clear: this is an exceptionally strong event, and it is still gaining power.

What matters most is what comes next. Carlo Buontempo, director of Copernicus, said the world is now in a stretch of months running above 1.5 degrees Celsius above pre-industrial levels, and with El Niño still intensifying, that condition is likely to persist into 2027. In 2015, nations agreed at the Paris climate talks to keep global warming well below 2 degrees and to pursue efforts limiting it to 1.5 degrees. The United Nations announced in September that the long-term 1.5-degree target would be missed within years. Buontempo's statement carried both warning and a narrow opening: crossing the Paris Agreement's limit is inevitable, he said, but how far temperatures overshoot and for how long remains within human control. Scientists emphasize that reducing greenhouse gas emissions from fossil fuels is crucial—not to prevent the overshoot entirely, but to shorten it and bring temperatures back down as quickly as possible. Experts predict this El Niño will push global temperatures to a new record in 2027, a milestone that will arrive whether or not the world has begun to meaningfully cut emissions.