A mass extinction some 250 million years ago — known as the Great Dying — was driven by a "volcanic winter" which originated in southern China and not, as previously believed, in Siberia, according to a new study.
Researchers believe the end-Permian mass extinction began with several degrees of rapid cooling, followed by a longer period of global warming which, until now, has been widely seen as the driving force behind the near-collapse of life on Earth.
The scientists, led by the Chinese Academy of Sciences and Nanjing University, said their findings served as a reminder of the possible effects of climate change today.
"[We] argue that this volcanism [in South China] would have produced several degrees of rapid cooling before or coincident with the more protracted global warming," they wrote in a research article published in the peer-reviewed journal Science Advances last week.
The prevailing view has been that eruptions in a large region of volcanic rock known as the Siberian Traps in today's Russia were solely responsible for the mass extinction.
In this scenario, the release of a massive amount of greenhouse and poisonous gases, like carbon dioxide and sulphur dioxide, from the large igneous region was enough to cause severe global warming.
But the new study argues that temporal links between the mass extinction and volcanic eruptions were largely based on sedimentary records from southern China and the researchers said the Siberian region contained no direct evidence of the event.
"Large-scale eruptions near the South China block synchronous with the end-Permian mass extinction strengthen the case that the Siberian Traps large igneous province may not have been the sole trigger," they said.
The researchers found more than a third of the erupted rocks and the entire solidified magma of the Siberian Traps occurred later than the mass extinction horizon, suggesting the region's volcanic activity would not alone have been sufficient to trigger the climate and environmental changes.
In contrast, their study presents evidence for extensive volcanic activity during the relevant time frame in today's southwestern Chinese provinces of Yunnan and Sichuan.
This included mineral and related deposits, notably copper and mercury, whose age coincided with the mass extinction. They were covered by layers of volcanic ash, which pointed to anomalies in their composition likely due to sulphur-rich emissions from nearby volcanic eruptions, they said.
Modelling suggested the eruptions released a massive amount of sulphur dioxide, which would lead to an immediate global average cooling of more than four degrees Celsius on a thousand-year timescale — a volcanic winter — followed by an abrupt warming in the end Permian, according to the study.
"Rapid cooling on top of longer-term warming increases the climatic extremes experienced by terrestrial ecosystems. This bolsters the case that environmental degradation due to rapid climate shifts was an important kill mechanism during the end-Permian biotic crisis," the team said.
Lead author Zhang Hua, a professor at the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences, said the ancient extinction had implications for global warming today.
What happened during the end-Permian period was similar to today's rapid climate warming due to carbon dioxide emissions from human activity, he said.
"The mass extinction took place following global warming in which the ocean's temperature increased by eight to 10 degrees."
Zhang said the impacts of ocean warming included sea deoxygenation, polar ice melting, extreme weather events and coastal flooding from rising sea levels.
"We could draw lessons from 250 million years ago on what effects climate change could have on the ecosystem, animals and humans to better cope with and adapt to the changes, and slow global warming."
This article was first published in South China Morning Post.