A new study strengthens the hypothesis that the El Niño phenomenon contributed to the great Permian-Triassic extinction, 250 million years ago.
During evolution, countless species have emerged and become extinct, but in five mass extinction events, the rate of extinction reached exceptional levels: Earth's biodiversity plummeted by at least 75% within a relatively short period - spanning 2 million years or less. These five mass extinctions were driven by various factors, including asteroid impacts, volcanic activity, and drastic sea level changes triggered by ice ages.
Even among the five major extinction events, the Permian-Triassic Mass Extinction, which occurred approximately 250 million years ago, stands out as exceptionally severe. Named after the two geological periods it straddles, this extinction wiped out about 90% of all species on Earth. Its exact cause remains unclear. Until now, it has been attributed to massive volcanic eruptions in the Siberian region that triggered global warming, but this theory has notable shortcomings: other volcanic eruptions of comparable scale did not cause extinction of such magnitude. Moreover, the extinction began before the onset of climate warming. What additional factors, then, contributed to this great extinction?
The extinction has been linked to massive volcanic eruptions in the Siberian region, which likely triggered global warming. Temperature trends during the hottest months of the Permian-Triassic extinction | University of Bristol and China University of Geosciences (Wuhan).
A Combination of Global Disasters
A new study suggests that El Niño, a recurring climatic phenomenon that influences Earth's entire climate system, played a significant role in the Permian-Triassic extinction. During El Niño years, the Pacific Ocean becomes warmer, global temperatures rise, and many regions experience drier-than-average conditions. El Niño also disrupts wind patterns and alters global precipitation trends. Typically, each decade includes both El Niño events and their counterpart, La Niña, while the climate system remains in a neutral state during periods when neither phenomenon prevails.
Today, El Niño episodes last only a few months to a few years at most, but this wasn’t always the case. Using computational models and geological measurements, researchers showed that at the end of the Permian period, El Niño events became significantly stronger and longer-lasting. Intense volcanic activity during the Permian-Triassic era released vast amounts of greenhouse gases into the atmosphere. The new study reveals that rising greenhouse gas concentrations caused extended El Niño events from mere months to nearly a decade, greatly magnifying their impact on the global climate system.
During El Niño years, the climate becomes significantly hotter and drier. The image shows soil displaying evidence of extreme aridity | University of Bristol and China University of Geosciences (Wuhan).
How did changes in El Niño contribute to such a massive extinction event? Researchers found that shifts in El Niño patterns had a profound impact on global temperatures and precipitation. As noted, El Niño years are typically hotter and drier than average. Prolonged El Niño episodes caused extended periods of extreme heat and drought on a global scale. While ecosystems could recover from short, mild El Niño events, they were devastated by the severe droughts associated with intense and prolonged El Niño episodes, known as "mega El Niño." These mega events led to widespread forest desiccation and likely triggered massive wildfires, resulting in widespread catastrophic loss of plant and animal species, reduced photosynthesis, and the release of additional greenhouse gases into the atmosphere.
The study sheds new light on the most catastrophic extinction event in Earth's history, suggesting a strong connection between atmospheric greenhouse gases, El Niño, and the global climate system. This research is particularly relevant today, as greenhouse gas concentrations in the atmosphere are once again on the rise—this time driven by human activities. Many scientists warn that this trend could drive Earth toward its sixth mass extinction. We must hope that by studying past extinction events, humanity may find knowledge needed to prevent history from repeating itself.