Fossil corals from the Galápagos reveal El Niño has intensified by about 36 per cent over the past 40 years, far beyond anything seen in the last millennium.
Researchers link this surge to rapid post-industrial warming, suggesting human-driven climate change is likely supercharging a key driver of global droughts, floods, wildfires and food insecurity worldwide.
El Niño has intensified by almost 36 per cent fossil corals have revealed, providing the strongest evidence that global warming is strengthening the climate pattern.
Scientists analysed a 1,000-year archive preserved in fossil corals from the Galápagos archipelago to conclude that El Niño has intensified over the past four decades, when compared to 1850.
“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 warming global temperatures,” said lead author Julia Cole, professor and chair of the University of Michigan Department of Earth and Environmental Sciences in a press statement. “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,” she added.
The study does not directly attribute the strengthening of El Niño to climate change. Rather, it suggests that the intensification coincided with rapid post-industrial warming, exceeding the natural variability of El Niño and putting forward the planet’s human-induced warming as the most probable possibility.
Along with other coral results studied in other parts of the Pacific, the findings indicate “There’s something about this important source of climate extremes that has already changed in recent decades,” said Kim Cobb, a climate scientist at Brown University who was not part of the study, in a statement published in Science.
El Niño, a natural phenomenon that, that occurs every 2-7 years, causes the tropical Pacific Ocean to become warmer than usual. Under usual circumstances, trade winds blow along the equator from east to west, pushing warm water from South America toward Australia. When these trade winds weaken, warm water expands eastward towards South America, triggering an El Niño event.
This shift influences atmospheric circulation, causing heavy rainfall to move from Indonesia to the central Pacific, inducing droughts in the western Pacific. The shift weakens the trade winds further, enabling El Niño conditions to remain for 1-2 years. Despite the fluctuations in temperature and precipitation being limited to the tropical Pacific, its impact is felt across the world.
In the US, the deserts in the Southwest receive more rain as storm tracks shift southwards, while rainfall reduces in the Northwest.
Similar changes are seen around the world leading to less rainfall or droughts in countries such as India and flooding in other parts that lead to crop failure. Wildfires also affect millions of people.
Forecasters have warned of a Super El Niño this year that may become the strongest in almost a century.
To study historic El Niño patterns, the researchers sampled cores from 13 corals, including living colonies and boulders of ancient coral, from the Galápagos Islands, the study said.
“Corals grow 1 to 2 centimetres (0.4 to 0.8 inches) per year by secreting layers of calcium carbonate. The chemistry of these layers provides a record of the seawater temperature in which the corals grew,” the statement said.
As El Niño repeats every few years, the researchers focused on core samples that were at least 20 years old specifically examining two aspects of the coral skeleton’s chemistry.
The first was the ration of the elements strontium to calcium which is directly linked to the temperature at which corals grew. The other was supplementing the results with ratio of oxygen isotopes, another indicator of temperature at this site.
They were left with a history of variations in temperature in the Galápagos—a location, Cole said, where El Niño has its largest impact. They saw that strong El Niños occurred in the last 40-50 years, whereas the El Niños before that period showed consistent patterns of lower intensity El Niños.
The authors analysed whether natural processes could lead to similar intensifications of the natural phenomenon over the past 1,000 years using climate models to simulate the last 1,000 years corroborating historical data, volcanic eruption information and solar variability. The simulations noted no major shifts in the El Niño suggesting that natural processes could not lead to such last changes.
The scientists underlined that their findings add the need to mitigate global warming.
Cole said, “El Niño is a really big source of climate extremes, and so if it’s getting stronger, the impacts are getting stronger. These impacts include droughts, floods, wildfires and food insecurity.”
She said that changes in the hydrologic cycle also lead to issues such as damage to infrastructure from floods that wipe out homes, highways or railroads, and health effects from diseases such as cholera.
“We believe global warming is supercharging El Niño, and if that’s true, then we expect stronger climate extremes that will amplify ecological, infrastructural and human losses. No country has the resources to be fully protected from these impacts. This is one more reason we need to move away from fossil fuels, the root cause of the problem,” added Cole.