The mass extinction that shows what happens when El Niño gets out of control – 09/19/2024 – Science
About 252 million years ago, the world suddenly warmed. In a geologically brief period of tens of thousands of years, 90% of species were wiped out.
Even insects, which are rarely affected by such events, suffered catastrophic losses.
The Permian-Triassic mass extinction, as it is known, was the largest of the “big five” mass extinctions in Earth’s history.
Scientists had generally attributed the mass extinction to greenhouse gases released by a vast network of volcanoes that covered much of modern Siberia in lava. But the volcanic explanation was incomplete.
In our new study, we show that a massive El Niño climate event in the world’s largest ocean contributed to climate chaos – and led to extinctions that spread across the globe.
It’s easy to see why they blamed volcanoes. The onset of the extinction coincides almost perfectly with the beginning of the second phase of volcanism in the region of the so-called Siberian magmatic provinces.
This led to acid rain, the loss of oxygen from the oceans and, most importantly, temperatures beyond the tolerance levels of almost all organisms. It was the largest episode of global warming in the last 500 million years.
But there were still open questions for proponents of this seemingly simple extinction scenario: When the tropics got too warm, why didn’t species migrate to cooler, higher latitudes (as is happening today)? If the warming was sudden and rapid, why did land species die out tens of thousands of years before species in the sea?
There have also been many cases of similarly large volcanic eruptions and even other episodes of rapid warming, but why have none of them caused an equally catastrophic mass extinction?
Our new study reveals that oceans have warmed rapidly across the world’s low and mid-latitudes.
Normally they get cooler as you move away from the tropics, but not this time. It simply became too hot for life in many places.
A world prone to extremes
Using state-of-the-art computer software, we were able to simulate what the climate and weather conditions were like 252 million years ago. We found that even before rapid warming, the world was prone to extremes in temperature and precipitation.
This is a consequence of all the landmasses forming, at the time, one huge supercontinent, Pangaea. This means that the climates we see today in the centre of the continents – dry, with hot summers and freezing winters – were amplified.
Pangaea was surrounded by a vast ocean, Panthalassa, whose surface oscillated between warm and cold periods over the years, much like the El Niño phenomenon in the Pacific today.
However, once mass Siberian volcanism began, and carbon dioxide in the atmosphere increased, these prehistoric El Niños became more intense and lasted longer, thanks to the Panthalassa Ocean being larger and able to store more heat.
These El Niños had a profound impact on life on Earth, and set off a chain of events that made the weather increasingly extreme. Temperatures rose, especially in the tropics, and severe droughts and fires caused the extinction of rainforests.
This, in turn, was bad news for the climate, as less carbon was stored by trees, allowing more carbon to remain in the atmosphere, leading to further warming and even stronger, longer El Niños.
These stronger El Niños caused extreme temperatures and droughts to be pushed out of the tropics towards the poles, and more vegetation died, and more carbon was released.
Over tens of thousands of years, extreme temperatures spread across much of the planet’s surface. Eventually, the warming began to harm life in the oceans, particularly the tiny organisms at the base of the food chain.
At the height of the crisis, in a world already warming thanks to volcanic gases, an El Niño would have raised average temperatures by another 4°C. That’s more than three times the total warming we’ve caused in the last few centuries. At that time, El Niño-affected climates would have regularly seen daytime temperature spikes of 60°C or more on land.
The future of El Niño
In recent years, El Niños have caused major changes in precipitation and temperature patterns across the Pacific and even beyond. A strong El Niño was one factor in record temperatures in 2023 and 2024.
Fortunately, these events usually only last a few years. However, in addition to human-caused warming, even these smaller-scale modern-day El Niños can be enough to push fragile ecosystems beyond their limits.
El Niño is expected to become more variable as the climate changes, although it should be noted that the oceans have not yet fully responded to current warming rates. No one is currently predicting another mass extinction on the scale of the one that occurred 252 million years ago, but this event offers a sobering snapshot of what happens when El Niño gets out of control.
* Alex Farnsworth is a meteorology researcher at the University of Bristol, UK.
David Bond is a paleoenvironmental scientist at the University of Hull, UK.
Paul Wignall is Professor of Palaeoenvironment at the University of Leeds, UK.
This article was originally published on the academic news website The Conversation and republished here under a Creative Commons license. Read the original version here (in English)
