Volcanic eruptions drove ancient global warming event

Volcanic eruptions drove ancient global warming event



One of the most extreme periods of global warming that led to the first primates appearing on Earth was caused by volcanic eruptions, experts say.

This upheaval 56 million years ago was the result of Greenland separating from Europe during the opening of the North Atlantic Ocean.

Previous studies have proposed that the ancient environmental event was caused by the release of carbon from frozen methane buried in rock.

Scientists believe that studying the disturbance could help them to understand how Earth behaves when faced with dramatic conditions within the climate today.



An international team of researchers wanted to determine the source of the atmospheric carbon that led to the Palaeocene-Eocene Thermal Maximum (PETM) event.

During the PETM, atmospheric carbon dioxide more than doubled and global temperatures rose by 5C, an increase that is comparable with the change that may occur by later next century on modern Earth.

To identify the source of carbon during the PETM, the researchers studied the remains of tiny marine creatures called foraminifera.

Their shells shed light on the environmental conditions present when they lived millions of years ago. 

By separating the different atomic masses, or isotopes, of the element boron in the shells, they tracked how the pH level of seawater changed during the PETM.

By combining this data with a global climate model, the team were able to work out the amount of carbon added to the ocean and atmosphere.

They concluded that volcanic activity during the opening of the North Atlantic was the dominant force behind the PETM.

Professor Andy Ridgwell from the University of California, who was part of the research team, said: 'While it has long been suggested that the PETM was caused by injection of carbon into the atmosphere and ocean, the mechanism has remained elusive until now.



'By combining geochemical measurements and a global climate model that my group has been developing for over a decade, we have shown that this event was caused almost entirely by carbon emissions from the Earth's interior.

'The amount of carbon released during this time was vast - more than 30 times larger than all the fossil fuels burned to date and equivalent to all the current conventional and unconventional fossil fuel reserves we could feasibly ever extract.'

The PETM produced a change in conditions on the planet so sudden that many ecosystems struggled to recover.



This caused a mass extinction that wiped out 40 to 60 per cent of deep sea creatures living on the ocean floor, as well as a boom to plankton near the ocean surface.

The mammals also enjoyed great success, appearing in Europe and North America for the first time.

It is thought many new mammalian forms of life including horses and our own branch of the evolutionary tree, the primates, appeared around this time.

An unexpected finding was that enhanced organic matter burial was important in ultimately sequestering the released carbon and accelerating the recovery of the Earth's ecosystem without massive extinctions.

Dr Ridgewell added: 'Studying the PETM helps us understand the mechanisms that aid recovery from global warming, thereby helping researchers reduce the uncertainties surrounding the Earth's response to global climate change.

'While it is encouraging that most ecosystems were able to adapt during the PETM, today's global temperature could be increasing at a rate that is too fast for plants and animals to adjust.'