Ancient shells from seabed show rising CO2 levels

Shells under the microscope
Tiny shells from the seabed were analysed by the scientists to determine CO2 levels

Microscopic shells have been used by geologists at the University of St Andrews to chart the earth’s climate over millions of years.

They have concluded that it is three million years since current carbon dioxide (CO2) levels were last experienced on earth.

The shells were extracted from mud samples taken from the deep ocean bed.

Experts then related the make-up of the shells with the acidity of the sea water and then atmospheric CO2 levels.

They predict that if the burning of fossil fuels continues to grow, CO2 levels within two generations will match those of around 50 million years ago when crocodiles roamed the Arctic.

Dr James Rae, co-author of the study, told BBC Scotland: “That record of CO2 changes in the past is really trying to tell us a message about where we’re headed in the future.

The shells looked at by the St Andrews University team were taken from different depths of mud samples, some of which were several kilometres deep.

After establishing their age, the shells were sifted from the mud and then broken down in the lab to reveal the chemical element – boron.

Research fellow Dr Hana Jurikova explained: “In this case, boron works as an indicator of ocean pH (its acidity level).

“Because the atmospheric CO2 and the ocean pH are closely coupled, knowing the ancient ocean pH enables us to understand how CO2 evolved over this time.”

The geologists say their findings are the most complete history of CO2 levels over the past 66 million years.

They say the last time it was at current levels, there was much less ice on Greenland and Antarctica, driving up sea level by around 20 metres.

The findings are part of a five year project, led by the University of St Andrews, which still has three years to run.

BBC News, 1 June 2021. Full article.

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