Earth’s biggest mass extinction event 250 million years ago shows what can happen when El Niño gets out of control

About 252 million years ago, the Earth suddenly warmed. Over a geologically short period of a few tens of thousands of years, 90% of species became extinct. Even insects, which are rarely affected by such events, suffered devastating losses. The Permian-Triassic mass extinction was the largest of the “Big Five” mass extinctions in Earth’s history.

Scientists have generally blamed the mass extinction on greenhouse gases released by a vast network of volcanoes that covered much of modern-day Siberia in lava. But the volcanic explanation was incomplete. Our new study shows that a major El Niño weather pattern in the world’s major oceans disrupted the climate and caused the extinction to spread across the planet.

It’s easy to see why volcanoes were blamed: the start of the extinction coincided almost perfectly with the beginning of a second phase of volcanic activity in an area known as the Siberian Traps. This led to acid rain, oxygen loss in the oceans, and most notably, temperatures that exceeded the tolerance levels of nearly all life. This was the largest global warming event in the past 500 million years.

The World 252 Million Years Ago

But proponents of this seemingly simple extinction scenario were left with unanswered questions: When the tropics got too hot, why didn’t species migrate to cooler, higher latitudes (as is happening now)? If the warming was sudden and rapid, why did land species go extinct tens of thousands of years earlier than marine species?

There have been many examples of similarly sized volcanic eruptions and rapid warming of the planet, so why didn’t any of these cause a similarly catastrophic mass extinction?

Our new research shows that low- and mid-latitude oceans around the world are warming rapidly. Typically, the further away from the tropics you go, the colder the waters get, but this wasn’t the case this time. Many places simply became too hot for life to survive.

A world prone to extremes

Using cutting-edge computer programs, they were able to simulate what the weather and climate was like 252 million years ago, and found that even before the rapid warming, the world was plagued by extremes in temperature and rainfall.

This was a result of all the landmasses at that time forming into one giant supercontinent, Pangaea, which meant the dry, hot summers and freezing winters we see in the centre of the continent today expanded.

Pangaea is surrounded by a vast ocean, the Panthalassa, whose surface has undergone alternating periods of warming and cooling over the years, much like today’s El Niño phenomenon in the Pacific Ocean. However, after the onset of major volcanic activity in Siberia and increased carbon dioxide in the atmosphere, the wider Panthalassa ocean was able to store more heat, making prehistoric El Niños more intense and lasting longer.

The strongest El Nino of today

These El Niños had a profound effect on life on land, setting in motion a series of events that made the climate increasingly extreme, especially in the tropics, where temperatures rose and tropical forests were killed by massive droughts and fires.

This was bad news for the climate: Less carbon was stored in trees, and more remained in the atmosphere, leading to more warming and stronger, longer-lasting El Niño events.

252 million years ago, before the crisis…

These strengthening El Niño events caused extreme temperatures and droughts to spread from the tropics to the poles, killing more plants and releasing more carbon. Over tens of thousands of years, extreme temperatures spread across much of the Earth’s surface. Eventually, the warming began to take a toll on marine life, especially the tiny organisms at the bottom of the food chain.

…and peak extinction

At the peak of the crisis, El Niño would increase average temperatures by an additional 4°C in a world already warmed by volcanic gases, more than three times the human-induced warming over the past few centuries. At that time, El Niño-affected climates frequently experienced daytime maximum land temperatures of over 60°C.

The future of El Niño

In recent years, the El Niño phenomenon has caused major changes in rainfall and temperature patterns around the Pacific Ocean and further afield. A strong El Niño event could contribute to record warming from 2023 to 2024.

Fortunately, such events usually only last a few years, but even the current minor El Niño event, combined with human-induced warming, may be enough to push fragile ecosystems over their limits.

El Niño is predicted to become more variable as the climate changes, but it should be noted that the oceans have not yet fully responded to the current rate of warming. At this point, no one predicts another mass extinction on the same scale as the one 252 million years ago, but that event provides an alarming snapshot of what can happen when El Niño gets out of control.

This article is republished from The Conversation under a Creative Commons license. Read the original article.