Recent research indicates that significant ocean warming from El Niño events played a crucial role in the largest mass extinction in Earth’s history, which occurred around 252 million years ago.
A study published today in Science, co-led by researchers from the University of Bristol and the China University of Geosciences (Wuhan), has provided new insights into the catastrophic impact of rapid climate change during the Permian-Triassic warming period, affecting marine and terrestrial life.
For many years, scientists have attributed this mass extinction to extensive volcanic activity in present-day Siberia, which released large amounts of carbon dioxide into the atmosphere, leading to rapid global warming that caused widespread ecological collapse.
However, the reason why land-based life, including plants and typically hardy insects, experienced similar devastation has been unclear.
Dr. Alexander Farnsworth, a Senior Research Associate at the University of Bristol and co-lead author, stated: “Climate warming on its own cannot account for such severe extinctions. As we observe today, when tropical regions become excessively hot, species tend to migrate to cooler areas. Our research highlights that elevated greenhouse gases not only raise overall temperatures but also increase climate variability, resulting in more extreme and unpredictable conditions that hinder survival.”
The Permian-Triassic disaster demonstrates that global warming is not only about unbearable heat but also involves drastic climate fluctuations over decades.
“Most species struggled to adjust to these conditions, yet fortunately a few managed to survive, which is why life on Earth continued. It was nearly a catastrophic end for life as we know it,” commented co-lead author Professor Yadong Sun from China University of Geosciences, Wuhan.
The extent of warming during the Permian-Triassic period was determined by examining oxygen isotopes in fossilized teeth of tiny extinct swimming organisms known as conodonts. By analyzing temperature variations from conodonts globally, the researchers identified a significant collapse of temperature differences in low- and mid-latitude regions.
Dr. Farnsworth, who employed innovative climate modeling in their study, remarked: “Essentially, it became excessively hot everywhere. The changes that affected climate patterns were pronounced, marked by much more intense and prolonged El Niño events compared to those witnessed today. Species simply weren’t able to adapt or evolve swiftly enough.”
In recent years, El Niño events have resulted in significant shifts in rainfall and temperature. For instance, the weather extremes that contributed to the June 2024 heatwave in North America saw temperatures soar approximately 15°C above normal. The year 2023-2024 also recorded some of the highest global temperatures due to a strong El Niño in the Pacific, worsened by human-induced CO2 emissions leading to severe droughts and wildfires worldwide.
“Fortunately, such climatic events have typically persisted for only one to two years. However, during the Permian-Triassic crisis, El Niño lasted much longer, resulting in a decade’s worth of widespread drought followed by years of flooding. Essentially, the climate was extremely erratic, making it very difficult for any species to adapt,” explained co-author Professor Paul Wignall, a palaeoenvironments expert at the University of Leeds.
The findings from their climate modeling also offer explanations for the large amounts of charcoal found in rock layers from that era.
“With a climate prone to drought, wildfires became increasingly common. The Earth was trapped in a state of crisis, where landscapes were burning and oceans were stagnating. There were no safe havens for life,” added co-author Professor David Bond, a palaeontologist from the University of Hull.
The researchers noted that while many volcanic events throughout Earth’s history have caused extinctions, none reached the magnitude of the Permian-Triassic event.
They found that the Permian-Triassic extinction was unique because these Mega-El Niño events created positive feedback loops within the climate, leading to exceedingly warm conditions that began in the tropics and spread outward, causing significant plant die-offs. Plants are crucial for absorbing CO2 from the air and form the base of the food chain; their demise severely impacts Earth’s ability to regulate atmospheric CO2 levels in response to ongoing volcanic activity.
This finding also sheds light on the puzzling timeline of the Permian-Triassic mass extinction, which saw land extinctions happen tens of thousands of years before those in the oceans.
“While the oceans initially shielded themselves from rising temperatures, the Mega-El Niño caused land temperatures to surpass the thermal tolerances of most species at a pace too rapid for them to adapt,” explained Dr. Sun.
“Only those species capable of migrating quickly managed to survive, and there weren’t many plants or animals that could do so.”
Mass extinctions, though infrequent, play a critical role in resetting Earth’s natural systems, leading to new paths for life and evolution.
“The Permo-Triassic mass extinction, although catastrophic, eventually paved the way for the rise of dinosaurs, which then became the dominant species, much like how the Cretaceous mass extinction facilitated the rise of mammals and ultimately humans,” Dr. Farnsworth concluded.
