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Earth's average surface temperature has risen by about 1° Celsius over the past half century. While the upward trend is unrelenting, dips and spikes along the way are common due to natural climatic anomalies. The spike in global temperature in 2023 was especially large, breaking the previous record by nearly 0.2°Celsius. This motivated several researchers including , and to dig into the mechanisms.

All three point in different ways to El Niño and La Niña-temporary warming and cooling events in the tropical Pacific Ocean that occur every few years. used global observations of sea surface temperature to uncover the ocean's role in the record heat of 2023, including a transition from a long-lasting La Niña to El Niño. showed how El Niño's far-reaching impact on seasonal climate anomalies-especially over North America-helped extend the global warming spike further across the year. Applying statistical analysis to a broad suite of global climate model simulations, confirmed that even in a world without carbon emissions, one-off spikes in global temperature just as large as that seen in 2023 are to be expected during El Niño years, and even more so when preceded by a long-lasting La Niña.

These studies underscore the importance of understanding how short-term, regional climate variability, such as El Niño, interacts with the relentless march of global warming to produce extreme global events like that of 2023.