New research reveals how El Niño caused the largest mass extinction in history

Massive ocean warming events such as El Niño played a key role in the largest extinction of life on planet Earth about 252 million years ago, a new study finds.

The study, published in Science and co-led by the University of Bristol and the China University of Geosciences (Wuhan), has shed new light on why the effects of rapid climate change during the Permian-Triassic warming were so devastating for all forms of life in the sea and on land.

Scientists have long linked this mass extinction to the massive volcanic eruptions that took place in what is now Siberia. The resulting carbon dioxide emissions rapidly accelerated global warming, leading to widespread stagnation and collapse of marine and terrestrial ecosystems.

But what caused life on Earth, including normally resilient plants and insects, to suffer so badly remains a mystery.

Dr Alexander Farnsworth, co-lead author and principal investigator at the University of Bristol, said: “Global warming alone cannot cause such devastating extinctions because, as we see today, when the tropics get too hot, species migrate to cooler, higher latitudes.

“Our research has revealed that increasing greenhouse gases are not only warming much of the planet, they are also increasing the variability of weather and climate, making the survival of life even more ‘wild’ and difficult.”

The Permian-Triassic catastrophe shows that the problem of global warming is not just a matter of unbearable heat, but also of climatic conditions that change dramatically over decades.

“Most life forms failed to adapt to these conditions, but fortunately a few things survived, without which we would not be here today. It was almost, but not quite, the end of life on Earth,” said co-senior author Professor Yadong Sun of the China University of Geosciences in Wuhan.

The extent of the Permian-Triassic warming was revealed by studying oxygen isotopes in the fossilized teeth of tiny, extinct swimming organisms called conodonts. By studying temperature records of conodonts around the world, the researchers were able to show a remarkable collapse in temperature gradients in low and mid-latitudes.

Dr Farnsworth, who used innovative climate modelling to assess the results, said: “In fact, it was too warm everywhere. The changes responsible for the climate patterns identified were profound, because El Niño events were much more intense and prolonged than those seen today. Species were simply not equipped to adapt or evolve quickly enough.”

In recent years, El Niño events have caused major changes in precipitation patterns and temperatures. For example, the weather extremes that caused the North American heatwave of June 2024, when temperatures were about 15 °C warmer than normal. The year 2023-2024 was also one of the warmest years on record globally due to a strong El Niño in the Pacific, which was further exacerbated by increases in human-caused CO2.₂ causing catastrophic droughts and fires around the world.

“Fortunately, until now, such events have only lasted for one or two years at a time. During the Permian-Triassic crisis, El Niño persisted for much longer, leading to a decade of widespread drought, followed by years of flooding. In effect, the climate was completely unstable and this makes it very difficult for any species to adapt,” said co-author Paul Wignall, professor of palaeoenvironments at the University of Leeds.

Climate modeling results also help explain the abundance of charcoal found in rock layers of this age.

“Wildfires become very common in drought-prone climates. The Earth found itself stuck in a state of crisis where the land was burning and the oceans were stagnant. There was nowhere to hide,” added co-author Professor David Bond, a palaeontologist at the University of Hull.

The researchers observed that throughout Earth’s history, there have been many volcanic events similar to those in Siberia, many of which have caused extinctions, but none have led to a crisis on the scale of the Permian-Triassic event.

They found that the Permian-Triassic extinction was so different because these mega-El Niños created a positive feedback on the climate that led to incredibly warm conditions from the tropics and beyond, causing vegetation to die back. Plants are essential for removing CO₂ of the atmosphere, as well as the base of the food web, and if they die, one of the Earth’s mechanisms for stopping CO also disappears.₂ accumulating in the atmosphere due to continued volcanism.

It also helps explain the puzzle about the Permian-Triassic mass extinction, which holds that the extinction on land occurred tens of thousands of years before the extinction in the oceans.

“While the oceans were initially protected from temperature increases, mega-El Niños caused temperatures on land to exceed the thermal tolerances of most species at such a rapid rate that they were unable to adapt in time,” Dr Sun explained.

“Only species that could migrate rapidly could survive, and few plants or animals were able to do that.”

Mass extinctions, while rare, are the heartbeat of Earth’s natural system, resetting life and evolution on different paths.

“The Permo-Triassic mass extinction, while devastating, would eventually see the emergence of dinosaurs as the dominant species, just as the Cretaceous mass extinction would lead to the emergence of mammals and humans,” Dr Farnsworth concludes.