The return of the El Niño climate phenomenon later this year will push global temperatures “out of bounds” and lead to unprecedented heatwaves, scientists have warned.
Early forecasts suggest El Niño will return later in 2023, exacerbating extreme weather across the globe and making it “very likely” global warming will exceed 1.5C. The hottest year on record, 2016, was driven by a major El Niño.
It’s part of a natural oscillation driven by ocean temperatures and Pacific winds that switches between El Niño, its cooler La Niña counterpart, and neutral conditions. The past three years have seen an unusual series of back-to-back La Niña events.
This year is already predicted to be hotter than 2022, which global datasets rank as the fifth or sixth hottest year on record. But El Niño occurs during the Northern Hemisphere winter and its warming effect takes months to be felt, meaning 2024 is much more likely to set a new global temperature record.
Greenhouse gases released by human activity have raised the average global temperature by about 1.2C to date. This has already led to catastrophic impacts around the world, from scorching heat waves in the US and Europe to devastating floods in Pakistan and Nigeria, harming millions of people.
“It is very likely that the next big El Niño will take us above 1.5C,” said Prof Adam Scaife, head of long-range forecasting at the UK Met Office. “The probability of the first year being 1.5C over the next five-year period is now about 50:50.”
“We know that with climate change, the impact of El Niño events will become stronger, and you have to add that to the effects of climate change itself, which is increasing all the time,” he said. “Put those two things together and we’re likely to see unprecedented heat waves during the next El Niño.”
The changing impacts of the El Niño-La Niña cycle can be seen in many regions of the world, Scaife said. “Science can now tell us when these things are coming months ahead. So we really need to use it and be more prepared, from the readiness of the emergency services to what crops to plant.”
Professor James Hansen of Columbia University in New York and colleagues said recently: “We predict that 2024 is likely to be off the charts as the warmest year on record. The current La Niña is unlikely to last a fourth year. Even a little bit of El Niño should be enough for a record global temperature.” China’s declining sun-blocking air pollution is also increasing heating, he said.
Two views of the same coral reef in Kiribati taken before and after the 2015-16 marine heat wave and strong El Niño: in May 2015 (L) and in June 2018 (R). Photo: Daniel Klaar/Victoria University/AFP/Getty Images
Although El Niño would intensify extreme weather, the degree of exacerbation was a matter of debate among scientists.
Prof. Bill McGuire of University College London, UK, said: “When [El Niño arrives]the extreme weather raging across our planet in 2021 and 2022 will fade into insignificance.” While Prof Tim Palmer of the University of Oxford said: “The link between extreme weather and global average temperature is not that strong [but] the thermodynamic effects of climate change will make the anomalies we get from an El Niño year that much more extreme.”
Climate modeling results released in early January by the Australian Bureau of Meteorology showed the country could go from three years of above-average rainfall to one of the hottest and driest El Niño periods on record, increasing the risk of severe heat waves, droughts and fires. In December, the US National Oceanic and Atmospheric Administration estimated the chances of an El Niño forming by August-October as 66%.
The scale of the likely El Niño was not yet clear. Professor Andy Turner of the University of Reading said: “Many seasonal forecast models suggest the arrival of moderate El Niño conditions from the summer of 2023.” The picture will be much clearer by June, scientists said.
The El Niño-La Niña phenomenon is the biggest cause of annual weather differences in many regions. In La Niña years, the east-west trade winds in the Pacific Ocean are stronger, pushing warm surface waters to the west and pulling deeper, cooler waters to the east. El Niño events occur when the trade winds weaken, allowing warm waters to spread back east, suffocating cooler waters and causing global temperatures to rise.
Nations bordering the western Pacific Ocean, including Indonesia and Australia, experience hotter and drier conditions. “You tend to get a lot of droughts, a lot of wildfires,” Scaife said, although China can suffer from flooding in the Yangtze Basin after major El Niños.
Monsoons in India and rains in South Africa may also be suppressed. Other regions, such as East Africa and the southern United States, both of which have experienced recent droughts, could see more rain and flooding. In South America, the southern regions are wetter, but the Amazon, which is already approaching a dangerous tipping point, is drier.
“The effects of El Niño may also be felt in the mid-latitudes of the Northern Hemisphere, with the possibility of wetter conditions in Spain from the summer onwards and drier conditions along the US East Coast next winter and spring,” Turner said.
Palmer said the biggest unanswered question is whether climate change favors more El Niño or more La Niña events: “This is extremely important for countries looking for long-term adaptation, and will need climate models with much higher resolution. This can only be done with larger computers.
Palmer and his colleagues have called for a $1 billion International Climate Modeling Center, similar to the Large Hadron Collider, to allow international particle physicists to do together what no one nation can do alone.
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