El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean that affects the climate of much of the tropics and subtropics. This natural phenomenon is important to study because of the socioeconomic impacts it can have on matters such as food security, agricultural production, human health and water resources, to name but a few.

With its strong preference to peak during boreal winter and rapidly decay in spring (known as “phase-locking”), and quasi-periodic oscillations of 2–7 years, historically, ENSO rarely maintains for long in either its cold phase (La Niña) or warm phase (El Niño). However, since the turn of the current century, three instances of so-called “double dip” La Niña events have occurred, in 2007–09, 2010–12 and 2020–22.

This succession of double-dip La Niña events is intriguing enough in itself; but now, based on updated data from several organizations issued in April 2022, it seems that the current event is likely to continue through the boreal summer and fall of 2022, suggesting a strong possibility of a third-year La Niña lasting from 202023.

“This would be the first third-year La Niña since the 1998–2001 event, which was the only such event observed since 1980,” explains Dr Xianghui Fang from Fudan University, China.

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