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A rapid rise in greenhouse gases around 56 million years ago resulted in sea surface temperatures as high as 40°C with significant impacts on marine life, according to new research published in the September edition of the scientific journal Geology.

The period, known as the Palaeocene-Eocene Thermal Maximum (PETM), lasted for around 170,000 years and saw the release of roughly the same volume of CO2 as expected from modern fossil fuel consumption.

Present-day planktonic foraminifera. Photo: GLOW Cruise Scientists

Present-day planktonic foraminifera.
Photo: GLOW Cruise Scientists

A team of researchers from universities around the country, led by Professor Paul Pearson of Cardiff University, made use of newly-extracted microscopic marine fossils called planktonic foraminifera. The tiny shells of these single-celled organisms contain different proportions of oxygen isotopes and these proportions are largely determined by the sea temperatures at the time.

By analysing exceptionally well-preserved PETM fossils from Tanzania the research team were able to reconstruct a picture of sea surface temperatures and changes in the abundance of planktonic life.

The research, conducted by Dr Tracy Aze, previously of Cardiff University and now a research fellow at the Oxford University Museum of Natural History, could have implications for the understanding of climate change in the future.

“The amount of CO2 that is predicted to be released from the Industrial Revolution to around 100 years from now is roughly equivalent to what happened in the PETM,” says Dr Aze. “But the big difference is the rate of release: today we are releasing greenhouse gases at a far faster rate than 56 million years ago. Nonetheless, the PETM shows us that rapid increases in CO2 in the atmosphere have significant impacts on global temperatures, with an associated local disappearance of marine life.”

It is the first time such well-preserved tropical foraminifera specimens have been available for this type of study and they reveal a picture of the effects of a substantial release of greenhouse gases into the atmosphere. By providing a partial analogue for current anthropogenic global warming, this research into the PETM informs the modelling of future climate change patterns.

Extreme warming of tropical waters during the Paleocene–Eocene Thermal Maximum.  Aze, Tracy; Pearson, Paul N; Dickson, Alex J; Badger, Marcus P S; Bown, PR; Pancost, Rich D; Gibbs, Samantha J; Huber, Brian T; Leng, Melanie; Coe, Angela J ; Cohen, Anthony S; Foster, Gavin L. – Geology, published online 25 July 2014