The Permian mass extinction could have been influenced by the Mega El Niño event

The end-Permian extinction, 250 million years ago, may have been amplified by an El Niño event that was much stronger and longer-lasting than anything we see today.

These giant El Niño events caused extreme changes in the climate, wiping out forests and many land animals. Alexander Farnsworth At the University of Bristol, UK.

The El Niño also set off a feedback process that helped make this mass extinction so bad, he said: “There's a knock-on effect that's making these kinds of El Niños stronger and lasting longer.”

The end-Permian extinction is thought to have wiped out about 90 percent of all species living at the time, making it the worst mass extinction in history, and is widely thought to have been caused by a massive volcanic eruption in what is now Siberia.

These eruptions heated rocks rich in fossil carbon, releasing huge amounts of carbon dioxide, causing extreme global warming. Oceans became stagnant and oxygen-depleted, killing marine life.

But this doesn't explain the whole story: in particular, terrestrial species began to go extinct tens of thousands of years earlier than marine species.

A variety of ideas have been proposed to explain this, from volcanic winters to a disappearing ozone layer, but the idea that an extreme El Niño might be involved arose from studies of past ocean temperatures based on oxygen isotopes in fossils. Yadong Sun At China University of Geosciences in Wuhan.

Now, Farnsworth and his colleagues have run computer models to explore what might have happened at the end of the Permian period that could explain Sun's findings.

Currently, El Niño occurs when warm water in the western Pacific Ocean spreads eastward across the ocean surface, creating an area of ​​anomalously warm water that heats the atmosphere and affects weather across the globe.

The researchers found that before the Permian extinction began, El Niño events were probably similar in strength and duration to today, meaning abnormally warm waters were about 0.5°C (0.9°F) hotter than average and the event lasted for several months.

But these events occurred in a huge ocean called the Panthalassa, which was 30 percent larger at the equator than the present-day Pacific Ocean. This means that the area of ​​unusually warm water during El Niño was much larger than it is today, and its impact on the planet was much greater.

According to the team's model, rising carbon dioxide levels at the end of the Permian period caused El Niño events to become stronger and last longer. These events caused extreme weather changes on land and killed forests, which stopped absorbing carbon dioxide and started releasing it, leading to further warming and more extreme El Niño events.

In the ocean, the temperature changes would have been less drastic, and marine life would have had an easier time migrating to avoid them. This is why the marine extinctions occurred after more intense global warming. “The deadly extreme global warming that caused the marine extinctions was made worse by these El Niños because they stripped away carbon sinks,” says Farnsworth.

At the peak of the extinctions, El Niño temperature anomalies reached up to 4°C (7.2°F), and each event lasted for more than a decade, he says.

It's unclear whether a similar event will occur in the future — computer models vary in their predictions about how El Niño will change as the planet warms, Farnsworth said — but because El Niño occurs in a warmer world, it's already having big effects.

“The recent El Niño event has caused record temperatures and sparked a lot of wildfires,” he says, “and what worries me most is the signs of tree death in the Amazon during this El Niño event.”

Research shows that under certain climate conditions, El Niño could cause extinctions, Pedro Dinezio According to a team of researchers from the University of Colorado Boulder, such giant El Niño events don't occur today because the Pacific Ocean is smaller than the Panthalassa.

“These results are really interesting for understanding the past, rather than the near future,” Dinezio says. “To understand what El Niño will bring, we need to look at past periods when the continents were positioned similarly to the present.”

“I think this is a compelling study.” Phil Jardine Researchers at the University of Münster in Germany have discovered the first direct evidence that the ozone layer disappeared during the Permian mass extinction.

“I don't think this event and other extinction drivers, including ozone depletion, are mutually exclusive,” he says. “The scary thing about the end-Permian extinction is that a lot of things were happening at the same time, and they seemed to feed off each other in cascading ways throughout the Earth system.”