New geochemical data provide evidence that pCO2 increased in response to volcanic out-gassing and remained high for around 1.5-2 million years.
The rate of environmental change occurring today is unprecedented compared to that which occurred during natural events in the Earth's history, a new study has claimed.
The study by researchers at the University of Bristol Cabot Institute in UK reconstructed the changes in atmospheric carbon dioxide (pCO2) during a global environmental change event that occurred about 120 million years ago.
New geochemical data provide evidence that pCO2 increased in response to volcanic out-gassing and remained high for around 1.5-2 million years, until enhanced organic matter burial in an oxygen-poor ocean caused a return to original levels.
"It has been suggested that the event we studied is a suitable analogue to what is happening today due to human activity and that a rapid increase in pCO2 caused ocean acidification and a biological crisis amongst a group of calcifying marine algae," said lead author Dr David Naafs.
"Our work confirms that there was a large increase in pCO2. The change, however, appears to have been far slower than that of today, taking place over hundreds of thousands of years, rather than the centuries over which human activity is increasing atmospheric carbon dioxide levels," said Dr Naafs.
"So despite earlier claims, our research indicates that it is extremely unlikely that widespread surface ocean acidification occurred during this event," he said.
Co-author Professor Daniela Schmidt emphasised that today's finding builds on one of the Intergovernmental Panel on Climate Change (IPCC)'s key conclusions: that the rate of environmental change occurring today is largely unprecedented in Earth history.
"This is another example that the current rate of environmental change has few if any precedents in Earth history, and this has big implications for thinking about both past and future change," she said.
The research was possible due to the exceptional Spanish section that the team analysed.
"The sediments at Cau accumulated very rapidly resulting in an expanded section. This allowed the high resolution multidisciplinary analysis that are the basis for this important study," said Professor Jose Manuel Castro of the University of Jaen in Spain.
The study was published in the journal Nature Geoscience.