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36,000 gigatons of carbon heralded history’s biggest mass extinction


Image of a large ridge made of volcanic rock.
Enlarge / Some of the massive volcanic deposits that are part of the Siberian Traps.

The end-Permian mass extinction was a big deal. It was the largest mass extinction event ever and occurred 252 million years ago. A whopping 90 percent of all marine species and around 70 percent of their terrestrial kin were killed off.

Over the years, there have been numerous efforts to look into this massive, world-changing event. The end-Permian mass extinction was coincident with mass eruptions in the Siberian Traps, and some potential scenarios include volcanism driving acid rain, volcanism triggering the burning of coal (which released greenhouses gases into the atmosphere), and a reduction in the availability of oxygen in the ocean, among others. However, a new paper relies on previously unused data and modeling to dig into the matter.

In all, the study found that 36,000 gigatons of carbon—mostly from volcanic sources—were released into the atmosphere over a relatively short span of 15,000 years. This period also saw the global average temperature rise a staggering amount, from 25ºC to 40ºC. While researchers previously explored volcanism and carbon as potential causes for the massive extinction, this work provides more insight into the event, said Wolfram Kürschner, a geologist at the University of Oslo and one of the authors of the paper.

“Until now, it was really difficult to quantify the amount of CO2 that was released to the atmosphere,” Kürschner told Ars.

Look to the past

According to Ying Cui, one of the paper’s coauthors and an assistant professor at Montclair State University’s Department of Earth and Environmental Studies, the authors studied the matter by looking at compound-specific carbon isotopes.

These samples were collected from sediments extracted from Norway’s Finnmark Platform, which is on the eastern part of the Barents Sea Shelf. According to Cui, these samples were quite well-preserved and allowed them to look at biomarker compounds from life in the ocean and on land during the critical period.

After looking at the data, the team deployed a series of models that allowed them to look at the source and amount of carbon emissions released during the period. “When you combine [the data and the modeling] together, they become very powerful, and they can reveal some new insights that we can’t really tell by looking at these aspects individually,” Cui told Ars.

Beyond the global warming, the increase in CO2 and changes in carbon cycle could have lowered the pH value of the world’s oceans. This acidification could be partly responsible for the die-off of marine lifeforms. Indeed, even current levels of ocean acidification with humanity’s carbon emissions (which are relatively mild compared to volcanic eruptions) are causing the shells of some marine organisms to dissolve.

According to Kürschner, this work could give us a glimpse into what might happen in the Anthropocene’s future if things get bad enough. The scale of carbon release and temperature increase are vastly different, but the research shows that dramatic warming in the world’s climate had a dramatic impact on the life living on the planet. “I think it’s like a wakeup call,” he said. “Let’s say we should take care.”

PNAS, 2021. DOI: pnas.2014701118 (About DOIs)



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