About 252 million years ago, extreme El Niño ocean warming events were a major driver of the largest mass extinction in our planet’s history. The Permian-Triassic warming events killed 80 to 90 percent of species living on Earth and offer a stark warning as the planet continues to warm. This new look at how ocean warming played a major role in this volatile time in Earth’s history is detailed in a study published September 12 in the journal Science.
The Great Dying
The Permian-Triassic mass extinction–also called The Great Dying–was triggered by massive volcanic eruptions in present day Siberia. The volcanoes spewed toxic gasses into the atmosphere and the increased carbon dioxide emissions rapidly increased temperatures around the globe. The Great Dying eventually paved the way for dinosaurs to dominate Earth, but it was even worse than the Cretaceous–Paleogene extinction that eventually wiped most of them out about 66 million years ago.
The increased carbon dioxide from the volcanoes and UV light radiation caused both marine and land ecosystems to break down. However, what caused plants and famously resilient insects on land to suffer as badly as those in the world’s oceans has remained a scientific mystery.
[Related: This tiger-sized, saber-toothed, rhino-skinned predator thrived before the ‘Great Dying.’]
“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,” study co-author Alexander Farnsworth, a meteorologist and climatologist at the University of Bristol in England, said in a statement. “Our research has revealed that increased greenhouse gasses 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.”
According to the team, this catastrophe shows that global warming isn’t just a matter of the planet becoming unbearably hot, but also causes conditions to swing wildly over a period of several decades.
“Most life failed to adapt to these conditions, but thankfully a few things survived, without which we wouldn’t be here today,” Yadong Sun, a study co-author and paleoclimatologist at China University of Geosciences in Wuhan, said in a statement. “It was nearly, but not quite, the end of life on Earth.”
A tooth that measures temperature
In the study, the team got a sense of the full scale of Permian-Triassic warming by studying oxygen isotopes in fossilized tooth material from some extinct swimming organisms called conodonts. These tiny marine invertebrates were less than an inch long and may be distantly related to living hagfish.
By using the oxygen isotopes to get a sense of the temperature changes that conodont samples from around the world experienced, the team built various climate models. The models indicate a remarkable collapse of temperature gradients in both the low and mid latitudes.
An animation of the monthly average surface temperature (in degrees Celsius) during the peak warmth of the crisis due to very high volcanic carbon dioxide emissions. CREDIT: Alex Farnsworth, University of Bristol“Essentially, it got too hot everywhere,” said Farnsworth. “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.”
Recently, El Niño events have caused major changes in precipitation patterns and global temperatures. It was behind the weather extremes that caused a record breaking heatwave in June in parts of the United States. 2023 was also the hottest year on record globally, partially due to a strong El Niño in the Pacific. This strong El Niño was exacerbated by increased human-induced carbon dioxide in the atmosphere driving wildfires and drought around the world.
[Related: The ‘living fossil’ that thrived during a mass extinction.]
“Fortunately such events so far have only lasted one to two years at a time,” study co-author Paul Wignall, a palaeontologist at the University of Leeds in England, said in a statement. “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.”
The climate modeling in the study also helps explain why so much charcoal is found in rock layers dating back 250 million years ago.
“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,” David Bond, a study co-author and paleontologist at the University of Hull in England, said in a statement. “There was nowhere to hide.”
Migrate to survive
The team also observed that there have been many volcanic events similar to the one in Siberia millions of years ago. Many of these have caused extinctions, but none of them led to an event as large as the Permian-Triassic event.
These mega-El Niños appear to have helped make the Permian-Triassic extinction so devastating. They created a positive feedback loop in the climate, which led to extremely warm conditions beginning in the tropics and moving outwards. This heat then killed most of the Earth’s plants, which were and still are essential for removing carbon dioxide from the atmosphere and the foundation of the global food web. If too many plants die, Earth’s mechanisms to stop carbon dioxide from building up in the atmosphere as a result of continued volcanism go with them.
The feedback loop also helps explain the way Permian-Triassic mass extinction on land occurred tens of thousands of years before extinction in the oceans.
“Whilst the oceans were initially shielded from the temperature rises, the mega-El Ninos caused temperatures on land to exceed most species’ thermal tolerances at rates so rapid that they could not adapt in time,” said Sun. “Only species that could migrate quickly could survive, and there weren’t many plants or animals that could do that.”
[Related: A boiling hot supercontinent could kill all mammals in 250 million years.]
While mass extinction events are rare, they have proven to be central to a natural system of resetting life. They also spur evolution.
“The Permo-Triassic mass extinction, although devastating, would ultimately see the rise of Dinosaurs becoming the dominant species thereafter,” said Farnsworth. “As would the Cretaceous mass extinction lead to the rise of mammals and humans.”