A global shift to an El Ni帽o climate pattern later this year could pave the way for the world to breach 1.5掳C of warming for the first time in 2024, according to the UK Met Office.
New modelling from the agency suggests the current three-year La Ni帽a phase will end in March and this looks likely to be followed by an El Ni帽o pattern later this year.
鈥淎t the moment, the vast majority of forecasts are going into El Ni帽o in the latter half of 2023,鈥� says Adam Scaife at the Met Office.
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El Ni帽o and La Ni帽a are terms used to describe fluctuations in Earth鈥檚 climate system, driven by changing sea surface temperatures in the equatorial Pacific.
El Ni帽o is declared when sea temperatures in the tropical eastern Pacific rise 0.5掳C above the long-term average. La Ni帽a describes the opposite side of the fluctuation, when eastern Pacific temperatures drop below average.
Both phenomena trigger shifts in weather patterns around the world, affecting everything from heatwave risks in Australia to rainfall patterns in Chile. Because El Ni帽o events bring higher than average temperatures, they can also temporarily drive up the global average temperature.
A shift later this year to a strong El Ni帽o that pushes Pacific sea surface temperatures to 3掳C above average could temporarily raise the global average temperature by 0.3掳C, says Scaife. 聽This would come on top of the existing 1.2掳C increase in global temperatures since pre-industrial times, caused by rising greenhouse gas emissions.
Taken together, it could mean average temperatures in 2024 could reach 1.5掳C above pre-industrial levels, he says. 鈥淚f you add on a big El Ni帽o鈥� then we鈥檙e going to get close, potentially, to the first year of 1.5 degrees,鈥� he says.
Countries set a goal to limit global warming to 1.5掳C in the 2015 Paris Agreement, but that aim would only be missed if such a temperature rise is sustained over a couple of decades.
Last month, the Met Office , an expectation partly driven by an anticipated swing to El Ni帽o.
A global shift to El Ni帽o could bring relief to parts of Chile, Argentina and the south-west US, which have suffered lengthy droughts as a result of La Ni帽a.
But it would probably cause disruption to Indonesia鈥檚 monsoon season, impacting rice production in the country, and increase the risk of severe heatwaves and wildfires in Australia. Warmer sea temperatures also bring a heightened threat of bleaching in tropical coral reefs.
at James Cook University in Townsville, Australia, says the prospect of a strong El Ni帽o later this year is 鈥渢errifying鈥� for the Great Barrier Reef. 鈥淚 would expect that the next strong El Ni帽o will have a very serious impact on the Great Barrier Reef given that we saw bleaching for the first time in La Ni帽a in early 2022,鈥� he says.
But some researchers caution it is too early to tell how strong any El Ni帽o might be. A mild El Ni帽o would raise global temperatures, but not enough to breach 1.5掳C.
鈥淚t鈥檚 probably a better than 50/50 bet that there will be an El Ni帽o next winter,鈥� says at the University of Washington in Seattle. 鈥淗ow big it鈥檚 going to be is anybody鈥檚 guess.鈥�
Others say it is too early to say for certain there will be an El Ni帽o this year. at the University of Colorado Boulder points out the uncertainties in predicting the occurrence of El Ni帽o this early in the year, before the so-called spring predictability barrier. They liken the accuracy of El Ni帽o prediction models to 鈥渨eather forecasting 30 years ago鈥�.
鈥淭his early in the year, I would not bank on an El Ni帽o happening,鈥� says DiNezio.
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