Scientists are calculating the chances of the world experiencing record temperatures this year as they assess the likelihood of the return of the El Niño weather phenomenon that is associated with heat and drought.
El Niño involves the warming of the Pacific Ocean’s surface, which drives changes in temperature and rainfall patterns across the globe.
The World Meteorological Organization warned this week that the probability of El Niño developing this year was increasing, and its re-emergence would “likely fuel higher global temperatures”.
There was “a 60 per cent chance” that El Niño would develop between May and July, rising to 80 per cent between July and September, it forecast.
The US National Oceanic and Atmospheric Administration also issued an “El Niño Watch” alert in April that concluded there was a 62 per cent chance of El Niño developing between May and July.
The return of El Niño would be a long-anticipated transition from the rare three-year cycle of the corresponding La Niña weather pattern — the opposite weather phenomenon that involves the cooling of the Pacific Ocean’s surface temperature.
This weather system was officially declared at an end by meteorologists earlier this year, after taking its toll with devastating floods in the US and Australia and catastrophic drought in Africa and South America.
Below-average rainfall in 2021 and 2022 was one factor that led to the record drought in the Horn of Africa, and was in part a result of the presence of La Niña.
“The unusually stubborn La Niña has now ended” and neither La Niña nor El Niño were active, said the WMO last week.
There had been a “significant increase” in Pacific Ocean sea surface temperatures since February, however, the group said.
Although three years of La Niña had acted as a temporary “brake” on global temperatures, the last eight years were the warmest on record, said Petteri Taalas, the WMO’s secretary-general.
“The development of an El Niño will most likely lead to a new spike in global heating and increase the chance of breaking temperature records,” he said.
A strong El Niño event occurred between 2015 and 2016, with 2016 the hottest year on record.
If El Niño develops, regions such as South America, the southern US and the Horn of Africa would be likely to experience increased rainfall and potential flooding, while the risk of drought would increase in regions including Australia and Indonesia.
The UN’s Food and Agriculture Organization said in April that it was “scrutinising” at-risk areas that might suffer food insecurity during an El Niño period and any “anticipatory action” that could be taken to mitigate the effects.
Potential FAO actions included liaising with government officials and putting seed reserves in place, depending on the severity of the situation.
Brazil and South Africa were among the cereal-producing countries at risk of abnormally dry conditions and potential crop failures during an El Niño year, for example, the group said.
For an El Niño event to be declared, equatorial Pacific Ocean temperatures need to rise above a certain threshold, while changes in the atmosphere, such as winds at the equator, must also be detected.
The onset of El Niño was “harder to predict a long time in advance”, said the EU’s Copernicus Climate Change Service. Forecasting what might happen is particularly challenging towards the start of the year during the transition away from La Nina to either neutral or El Niño.
On Friday, the World Weather Attribution group of scientists concluded that climate change made this year’s record-breaking April heatwave in Spain, Portugal, Morocco and Algeria “at least 100 times more likely”.
The levels of heat recorded “would have been almost impossible” without human-driven warming, it said. Temperatures have already risen by at least 1.1C in the industrial era.
