Mega-El Niño events triggered the largest extinction on Earth

September 13 () –

According to new research, El Niño events that caused massive warming of the oceans were key to causing the largest extinction of life on Earth about 252 million years ago.

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 in the Permian-Triassic warming were so devastating for all life forms in the sea and on land.

Scientists have long linked this mass extinction to vast volcanic eruptions in what is now Siberia. The resulting carbon dioxide emissions rapidly accelerated climate warming, resulting in widespread stagnation and collapse of marine and terrestrial ecosystems.

But what caused life on land, including usually resilient plants and insects, to suffer just as badly remains a source of mystery.

Dr Alexander Farnsworth, co-lead author and senior research associate at the University of Bristol, said in a statement“Global warming alone cannot cause such devastating extinctions because, as we see today, when the tropics become too warm, species migrate to cooler, higher latitudes.

“Our research has revealed that increasing greenhouse gases not only make most of the planet warmer, but also increase weather and climate variability, which makes it even more ‘wild’ and difficult for life to survive.”

The Permian-Triassic catastrophe shows that the problem of global warming is not just a matter of it becoming unbearably hot, but also a case of conditions that fluctuate uncontrollably over decades.

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

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 noticeable collapse of temperature gradients at low and mid latitudes.

Dr Farnsworth, who used pioneering climate models to assess the findings, said: “Basically, It was too hot everywhere. The changes responsible for the identified climate patterns were profound because there were much more intense and prolonged El Niño events than those observed today. Species were simply not equipped to adapt or evolve quickly enough.”

In recent years, El Niño events have caused significant changes in rainfall and temperature patterns. For example, the extreme weather events that caused the June 2024 heat wave in North America, when temperatures were around 15°C higher 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 human-induced increases in CO2, leading to catastrophic droughts and fires around the world.

“Fortunately, so far these phenomena have only lasted one or 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 so variable and that makes it very difficult for any species to adapt,” says co-author Paul Wignall, a professor of palaeoenvironments at the University of Leeds.

The results of climate modeling also help explain the abundance of charcoal found in rock layers from that time.

“Wildfires become very common if you have a drought-prone climate. The Earth was caught in a state of crisis where the land was burning and the oceans were stagnating. “There was nowhere to hide,”added co-author Professor David Bond, a palaeontologist at the University of Hull.

The researchers noted that there have been many volcanic events similar to those in Siberia throughout Earth’s history, and many caused extinctions, but none 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 in the climate that led to incredibly warm conditions starting in the tropics and then beyond, which resulted in the death of vegetationPlants are essential for removing CO2 from the atmosphere as well as the base of the food web, and if they die, so does one of Earth’s mechanisms for stopping the buildup of CO2 in the atmosphere as a result of continued volcanism.

This also helps explain the Permian-Triassic mass extinction riddle, according to which extinction on Earth occurred tens of thousands of years before the extinction in the oceans.

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