A new study links the largest mass extinction, which occurred 252 million years ago during the Permian-Triassic period, to climate warming resulting in extreme weather events.

Scientists have long linked the Permian-Triassic mass extinction to vast volcanic eruptions in what is now Siberia. The large carbon-dioxide emissions rapidly accelerated climate warming, causing widespread ocean acidification, collapse of ocean currents and resulting in the loss of an estimated 96 percent of all marine species. But it wasn't clear why also terrestrial ecosystems suffered so much, with an estimated 75 percent loss of all species living on land.

A new study, coauthored by an international and multidisciplinary team of scientists, has shed new light on why the Permian-Triassic warming was so devastating for all forms of life in the sea and on land.

Co-lead author Dr. Alexander Farnsworth, Senior Research Associate at the University of Bristol, explains that, "climate warming alone cannot drive such devastating extinctions because, as we are seeing today, when the tropics become too hot, species migrate to the cooler, higher latitudes."

"Our research has revealed that increased greenhouse gases don't just make the majority of the planet warmer, they also increase weather and climate variability, making it even more 'wild' and difficult for life to survive."

The scale of Permian-Triassic warming was revealed by studying oxygen isotopes in the fossilized tooth material of tiny extinct swimming organisms called conodonts. By studying the temperature record of conodonts from around the world, the researchers were able to show a remarkable rise of temperatures in the low and mid latitudes, resulting in chaotic oceanic circulation patterns.

"Essentially, it got too hot everywhere. The changes responsible for the climate patterns identified were profound because there were much more intense and prolonged El Niño events than witnessed today. Species were simply not equipped to adapt or evolve quickly enough," concludes Farnsworth.

In recent years, El Niño events have caused major changes in rainfall patterns and temperature. For example, the weather extremes that caused the June 2024 North American heat wave when temperatures were around 15 degrees hotter than normal. 2023-2024 was also one of the hottest years on record globally due to a strong El Niño in the Pacific, which was further exacerbated by increased human-induced carbon-dioxide driving catastrophic drought and fires around the world.

"Fortunately, such events so far have only lasted one to two years at a time. During the Permian-Triassic crisis, El Niño persisted for much longer, resulting in a decade of widespread drought, followed by years of flooding. Basically, the climate was all over the place and that makes it very hard for any species to adapt," explains coauthor Paul Wignall, Professor of Paleoenvironments at the University of Leeds.

"Wildfires become very common if you have a drought-prone climate. Earth got stuck in a crisis state where the land was burning and the oceans stagnating. There was nowhere to hide," adds coauthor Professor David Bond, a paleontologist at the University of Hull.

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

This extinction was so different because these Mega-El Niños created positive feedback on the climate which led to incredibly warm conditions starting in the tropics and then beyond, resulting in the dieback of vegetation. Plants are essential for removing carbon-dioxide from the atmosphere, as well as the foundation of the food web, and if they die, so does one of the Earth's mechanisms to stop carbon-dioxide building up in the atmosphere as a result of continued volcanism.

This hypothesis also helps explain why the extinction on land occurred tens of thousands of years before the mass extinction in the oceans.

"While the oceans were initially shielded from the temperature rises, the mega-El Niños caused temperatures on land to exceed most species' thermal tolerances at rates so rapid that they could not adapt in time. Only species that could migrate quickly could survive, and there weren't many plants or animals that could do that," explains co-lead author Professor Yadong Sun, China University of Geosciences, Wuhan.

Extinction events on this scale, paleontologists recognize five big mass extinctions in the fossil record, are the heartbeat of the Earth's natural system resetting life and evolution along different paths.

"The Permo-Triassic mass extinction, although devastating, would ultimately see the rise of dinosaurs becoming the dominant species thereafter, as would the Cretaceous mass extinction lead to the rise of mammals, and humans," concludes Farnsworth.

The full study "Mega El Niño instigated the end-Permian mass extinction" was published in the journal Science.

Additional material and interviews provided by the University of Bristol.