Fossil shells reveal details of historic climate warming

A climate warming event 56 million years ago resulted from the release of greenhouse gases, most likely from a volcanic eruption. The warming event, the Paleocene-Eocene Thermal Maximum (PETM), also triggered ocean acidification. A new study shows that just before the PETM there was a short, causal burst in atmospheric CO2, with carbon levels similar to ours today. 

“The PETM is an important geologic climate event because it is one of best comparisons to current climate change and can help inform us how the Earth System will respond to current and future warming,” explained study lead author Dr. Tali Babila, a postdoctoral research associate at the University of Southampton.

To study the historic levels of atmospheric carbon, the scientists looked to the shells of microscopic sea creatures called foraminifera. First. foraminifera were collected in sediment core drillings off the eastern United States. Using a laser, the fossilized shells were vaporized and the pH levels were measured, thus revealing the extent of acid in the ocean and carbon in the atmosphere.  

“This had previously been suggested as a possible trigger for the large scale global warming that followed but scientists lacked a direct measure of carbon dioxide until this study,” explained Dr. Babila, “Usually, this type of analysis would require thousands of fossils which would not have been possible because of the scarcity of samples. Our novel application of the laser sampling technique is a major geoscience advancement bringing new and incredible detail never before seen in Earth’s past.”

The carbon levels revealed a portrait of an Earth very similar to ours now in terms of greenhouse gases and global warming. Seeing this change in the past may allow us to plan better for the future. 

“Whilst natural geological processes such as rock weathering and carbon burial eventually meant Earth eventually recovered from the PETM, it took hundreds of thousands of years,” said Dr. Babila. “So this is further proof that urgent action is needed today to rapidly cut the amount of carbon being release into the atmosphere to avoid long-lasting effects.”

The study is published in the journal Science Advances.

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By Zach Fitzner, Earth.com Staff Writer