Molecular fossils reveal secrets of Earth’s recovery from ancient global warming event

Scientists have uncovered new evidence from one of Earth’s most extreme ancient warming events, revealing how the climate may recover long after human-driven CO₂ emissions cease.

About 56 million years ago, during a period known as the Palaeocene–Eocene Thermal Maximum (PETM), the planet experienced a dramatic spike in temperatures triggered by a rapid release of greenhouse gases.

The PETM saw the highest global temperatures in the last 65 million years, and surface ocean temperatures reached over 20 degrees Celsius in the North Pole for hundreds of thousands of years.

The study, led by the University of Southampton, examined molecular fossils and climate model data to understand more about how the Earth system eventually stabilised after the warming.

Dr Gordon Inglis, Royal Society Dorothy Hodgkin Fellow and Principal Research Fellow in the School of Ocean and Earth Science, led the research, which is published in Nature Geoscience.

He said: “By studying molecular fossils in ancient sedimentary rocks, we found that carbon from land – from plants and soils – was eroded and transported by rivers into the sea where it was buried in sediments, locking some carbon away for long periods.

“This suggests that during past warm climates, more land-derived carbon was transferred into the ocean and buried than was previously thought.”

Dr Jordon Hemingway, co-author of the study, from ETH Zurich in Switzerland, added: “This process may have acted as a stabilising climate feedback, helping to gradually reduce atmospheric carbon levels over thousands to tens of thousands of years.”

By transferring carbon from land to ocean sediments, the Earth system may have been able to recover more efficiently from the intense warming.

Dr Emily Hollingsworth, Research Fellow at the University of Southampton and co-author of the study, said: “Our findings carry important implications for current global warming, because this ancient warming interval is a potential parallel to today’s human-driven climate change. Many leading climate models do not currently account for this type of carbon transfer and burial, so they could be overlooking a potentially significant long-term carbon sink.”

The study also highlights that the burial of terrestrial carbon in marine environments is an underappreciated natural process. Better understanding of this process could improve predictions of how the planet responds to rapid carbon releases.

Dr Inglis explained: “While our research shows what happened millions of years ago, it suggests that similar processes could play a role in Earth’s long-term recovery from human-caused carbon dioxide emissions.”