In the waters of the far-eastern equatorial Pacific – close to the South American coast – sea-surface temperatures are beginning to rise, prompting some climate scientists to believe the world could be heading for another El Niño in close succession to the previous event which ended last year.

This diagram illustrates the observed sea surface temperature for a central region of the tropical Pacific (in black), and the evolution predicted by the Met Office dynamical long-range ensemble forecast system (in red). A typical threshold for El Niño is for the sea surface temperature anomaly to be above 0.5 °C.

The last El Niño, which peaked in the winter of 2015-2016, was the joint strongest event on record. It had impacts around the world and the heat released from it added to existing climate change to break global surface temperature records in 2015 and 2016.

Prof Adam Scaife, head of long-range prediction at the Met Office Hadley Centre said: “The El Niño–La Niña cycle hasn’t been very active this winter, but Met Office predictions and those from some other centres are suggesting an increased risk of an El Niño developing by the summer.”

It isn’t unknown for El Niños to occur in close succession: events developed just two years apart in 1963 and 1965, and have even developed in consecutive years before, in 1986 and 1987. However, the level of warming in current predictions of the tropical Pacific is unusual for this time of year.

Commenting on the likelihood of another El Niño peaking at the end of this year, Prof. Scaife urged caution: “It is very early days and forecasts made at this time of year have great uncertainty, so we are just flagging the raised risk of an event at this stage, given the global consequences if it does occur.”

Any El Niño event (which is the warm phase of the El Niño-Southern Oscillation) has impacts on the global climate. If an El Niño does grow by summer some of the earliest impacts will be on the Atlantic hurricane season and the Indian monsoon, both of which tend to weaken during a developing El Niño.

You can learn more about the El Niño – La Niña cycle and its impacts on our web pages.

The World Meteoroligical Organization’s ENSO outlook is available here.