An intensifying El Nino pattern set an all-time temperature high in a key Pacific zone in September and could help make this year the hottest globally on record, the director of the EU's climate monitor said Monday.
Global forecasters have been warning for months that this El Nino would likely become the strongest ever observed and the latest record has tumbled even before the episode's expected peak later this year.
The warming phase of a natural climate cycle, El Nino temporarily raises sea temperatures in the tropical Pacific, triggering changes in weather that can increase the risk of drought and flooding, and exacerbate man-made global warming.
The Copernicus Climate Change Service said sea surface temperatures in a tell-tale El Nino monitoring region of the Pacific, known as Nino3.4, had reached an "all-time high" of 29.70C last month.
This exceeded the peak temperatures of previously strong El Nino events of 1982/1983, 1997/1998 and 2015/2016, the EU monitor said.
This year's El Nino, which emerged in June, is "very exceptional" but it is too early to say whether it is the strongest ever observed, Copernicus director Carlo Buontempo told AFP.
As climate change raises ocean temperatures, it can make recent El Nino events appear stronger than past ones, complicating historical comparisons.
Copernicus said it had adopted a new index, which accounts for the warming of tropical oceans, that suggested the current event is not yet stronger than past ones.
"It's a very large event even in that metric," Buontempo said. "This very large event today is happening in a much warmer climate."
Not all forecasters use the same scale to interpret El Nino.
On Friday, Japan's weather agency said that El Nino conditions had reached their "strongest intensity on record".
Record ocean temperatures
As El Nino gathers strength, global average sea surface temperatures hit a record 21.05C for September, topping the previous high of 20.92C for the same month in 2023, according to Copernicus.
Experts have warned that this El Nino, combined with human-induced climate change, could make 2027 the hottest year on record as heat stored in the Pacific is released into the atmosphere.
The weather phenomenon, which typically occurs every two to seven years and lasts around nine to 12 months, can drive world temperatures higher the year after its peak.
But Buontempo said even 2026 could wind up a record breaker as this El Nino builds toward its peak.
"If we follow the the pattern we have seen in the past, we may have a record-breaking 2026, followed by a record-breaking 2027," he told AFP.
After a record-breaking August, the world experienced its second hottest September ever observed, with surface air temperatures averaging 16.27C, the EU service said.
September was 1.63C hotter than the pre-industrial average, a period defined as 1850-1900. It was the second consecutive month that temperature rises exceeded 1.5C.
Buontempo said temperatures would probably remain 1.5C above normal into early next year
The last El Nino event helped make 2024 the hottest year on record after a series of months of temperatures exceeding 1.5C, he said.
But while El Nino plays a role, "the ultimate cause of the rise and the exceedance of 1.5C are anthropogenic emissions of greenhouse gases," Buontempo said.
Nations agreed at the 2015 UN climate talks in Paris to keep global warming "well below" 2C above pre-industrial levels, while pursuing efforts to limit it to 1.5C, in order to limit the effects of climate change.
But the United Nations declared in September that the long-term 1.5C target would be missed in a matter of years.
Scientists say it is crucial to reduce greenhouse gas emissions from fossil fuels to limit the period of "overshoot" above 1.5C and bring temperatures back down as quickly as possible.