Global weather and climate agencies have forecast the 2026-27 El Nino with a greater than 90 per cent chance to reach ‘very strong’ or near-record levels.
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El Nino events, the climate pattern associated with warmer ocean temperatures and more extreme events, has become about 40 per cent stronger over the past 40 years, compared to the pre-industrial era, according to a study.
Researchers, including those from the University of Michigan in the US, examined modern and ancient corals in the Galápagos Islands, located in the Pacific Ocean around 1,000 kilometres from the coast of Ecuador in South America.
The findings published in the journal Science show that El Niño events in the last four decades were stronger than any in the 1,000 years prior to about 1850, when humans began impacting the climate with greenhouse gases.
"We don't see a time in the past where El Niños have been as strong as today, and we show that the strength of El Niño changes in parallel with the warming of global temperature," lead author Julia Cole, professor and chair of the University of Michigan's department of earth and environmental sciences, said.
"Our findings tell us that the big El Niño events of the last 40 years are not normal in the context of the last thousand years," Cole said.
Most of the world's weather and climate is governed by the El Niño–Southern Oscillation (ENSO) in the tropical Pacific Ocean, of which El Nino — the warm cycle — that raises sea surface temperatures and is said to drive extreme weather around the world.
La Nina is the cool counterpart, and a typical ENSO cycle can last 2-7 years.
Global weather and climate agencies have forecast the 2026-27 El Nino with a greater than 90 per cent chance to reach 'very strong' or near-record levels.
"The question is not whether the current El Niño is going to happen, but how bad is it going to be, and how bad will the impacts be?" Cole said.
"This event is superimposed on global warming, and it's likely to supercharge the temperature increase that we would normally see from greenhouse gases. There are forecasts that we might get as hot as 1.7 or 1.8 degrees Celsius above pre-industrial temperatures, which is quite a bit higher than the current record," the lead author added.
The researchers sampled cores from 13 corals, including living colonies and boulders of ancient coral, from the Galápagos Islands. Corals grow one to two centimetres per year, secreting layers of calcium carbonate — its chemistry provides a record of seawater temperatures in which the corals grew.
El Niño extremes occur every few years, so the researchers focused on core samples that spanned at least 20 years. Sampling the cores a millimetre at a time, the group measured two aspects of the coral skeleton's chemistry.
Ratio of the elements strontium to calcium was analysed, which depends on the temperature at which the coral grew. The results were supplemented with an analysis of the ratio of oxygen isotopes, also a measure of temperature at this site.
A history of variations in temperature revealed in the Galápagos — a location, Cole says, where El Niño has its largest impact. The team saw that strong El Niños occurred in the last 40 to 50 years, whereas the El Niños prior to that time period showed "a pretty consistent pattern of lower intensity El Niños." The researchers also analysed climate models simulating the last thousand years with histories of volcanic eruptions and solar variability. The models found no large shifts in El Niño that suggested natural processes could create such large changes.
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