Ocean acidification to hit ‘unprecedented levels’

The world’s oceans are set to become more acidic than at any time in the last 14 million years if CO2 emissions continue at their current levels, a new study has found.

This could pose severe risks to marine life, with the shells of some animals already found to be dissolving as oceans absorb greater amounts of carbon and become more acidic.

It is predicted that ocean acidity could increase 75% by 2100 under a business-as-usual scenario, reaching levels last seen in the Middle Miocene Climatic Optimum period.

Cardiff University’s professor Carrie Lear, who co-authored the study, said that seawater is already probably more acidic than it has been for the last two million years.

“Understanding exactly what this means for marine ecosystems requires long-term laboratory and field studies, as well as additional observations from the fossil record,” she added.

The world’s oceans dissolve around one-third of the CO2 released by burning coal, oil and gas, absorbing approximately 525 billion tons since the beginning of the industrial era.

Published in the journal Earth and Planetary Science Letters, the Cardiff University study tracks ocean acidity and atmospheric CO2 levels over the past 22 million years through fossil analysis.

The findings allowed the researchers to forecast the pH level of oceans far into the future, predicting a fall from 8.1 to 7.8 by the end of this century if carbon emissions continue unabated.

Each drop of just 0.1 pH units represents a 25% increase in acidity, while the researchers also expect atmospheric CO2 to be near 930 parts per million under the business-as-usual scenario, compared to around 400 million today.

Study lead author, Dr Sindia Sosdian, said: “Our new geological record shows us that, on our current emission trajectory, oceanic conditions will be unlike marine ecosystems have experienced for the last 14 million years.”

The study was funded by the UK’s Natural Environmental Research Council, and also included researchers from the University of Southampton, University of St Andrews and the University of California.

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