September 19th 2024.
Around 250 million years ago, a catastrophic event almost wiped out all life on Earth. It was known as the Great Dying and it all began in the water. This event, which occurred around the same time as the Permian-Triassic extinction, wiped out more than 90% of life on Earth. Many people might assume that it was caused by a tsunami, a natural disaster that can cause massive loss of life. However, researchers now believe that it was even more deadly than the asteroid that wiped out the dinosaurs.
Scientists have long believed that the massive release of carbon dioxide from volcanic activity in the Siberian Traps region, which is now part of Russia, was the main cause of the Great Dying. This caused higher temperatures, acid rain, and ocean acidification, resulting in low levels of oxygen in the ocean and the death of marine creatures. However, a new research paper suggests that another factor may have played a significant role.
According to the study published in the journal Science, mega El Niños, which are the warm phase of the El Niño-La Niña Southern Oscillation, occurred during the Permian-Triassic crisis. These El Niños caused drastic changes in climate and resulted in the death of forests and many land animals. El Niño is a term used to describe the warming of sea surface temperatures that occurs every few years in the central-east equatorial Pacific. During this time period, El Niños were more intense and lasted longer, causing widespread droughts and flooding.
The lead author of the study, Professor Paul Wignall from the University of Leeds, explained that the extreme climate swings during this time made it difficult for any species to adapt. Co-lead author Dr Alexander Farnsworth from the University of Bristol added that the increase in greenhouse gases not only made the planet warmer, but also led to more unpredictable and severe weather patterns, making it even more challenging for life to survive.
El Niño and its counterpart, La Niña, are terms used to describe the biggest fluctuation in the Earth's climate system. El Niño is declared when sea temperatures in the tropical eastern Pacific rise 0.5°C above the long-term average, while La Niña occurs when there are cooler than average sea surface temperatures in the equatorial Pacific. In recent years, these phenomena have caused major changes in weather patterns and temperatures. For example, the El Niño in 2024 led to extreme weather conditions in North America, with temperatures 15°C hotter than normal.
The end-Permian extinction saw the loss of around 90% of all species alive at the time. While the theory of volcanic eruptions seemed to explain the event, it did not account for everything. Land species started going extinct tens of thousands of years earlier than marine species. To explain this, some researchers proposed that volcanic winters or the loss of the ozone layer may have played a role. However, Professor Yadong Sun from the China University of Geosciences suggested that extreme El Niños may also have been a contributing factor. The team then ran computer models to explore this possibility.
The researchers found that before the mass extinction, El Niños were similar in intensity and duration to those seen today. However, in the massive ocean called Panthalassa, which was 30% wider at the equator during the Permian era, these events had a more significant impact. As carbon dioxide levels rose, the El Niños became stronger and longer, leading to extreme swings in weather on land that killed off forests. This, in turn, caused the release of even more carbon dioxide, leading to further warming and more severe El Niños.
In the ocean, many animals were able to migrate to avoid the warming temperatures, which is why marine extinctions occurred later when global warming became more intense. Dr Sun noted that while most life failed to adapt to these conditions, a few species did survive, without which humans would not be here today. He added that it was almost the end of life on Earth, but not quite. As the El Niños worsened, they took away the carbon sink, leading to the death of many marine animals. By the peak of the extinction, the temperature during El Niños was up to 4°C higher, and each event lasted for more than a decade. Dr Farnsworth concluded that the Permo-Triassic mass extinction, while devastating, ultimately led to the rise of dinosaurs as the dominant species. This pattern has been seen in other mass extinction events, such as the Cretaceous extinction, which led to the rise of mammals and eventually, humans.
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