When we think of CO2 emissions, we generally tend to think of air pollution and global warming; we tend to ignore the fact that a huge part of all the CO2 emissions is absorbed by the oceans, and the oceans are becoming more and more acidic. The process is just getting started, and it’s gonna get worse – fast.

The deep-sea benthic foram Aragonia velascoensis went extinct about 56 million years ago as the oceans rapidly acidified. (Ellen Thomas/Yale University)

Ocean acidification is the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere. Out of the total CO2 released by humans, 30-40% is absorbed by the oceans. A new study has analyzed sea floor sediments drilled off the coast of Japan and has concluded that ocean acidification has soared in the past decades, and the process is just starting – by 2100, our oceans will be twice as acidic as they should be (read: as they were before the industrial revolution).

Studying the paleoclimate is essential for making climate predictions. Paleoclimatologists often look to a period called the Paleocene-Eocene Thermal Maximum (PETM), a period when huge quantities of CO2 were emitted. The cause of that emission is unknown.

“We are dumping carbon in the atmosphere and ocean at a much higher rate today—within centuries,” said study coauthor Richard Zeebe, a paleoceanographer at the University of Hawaii. “If we continue on the emissions path we are on right now, acidification of the surface ocean will be way more dramatic than during the PETM.”

Ocean acidification is already affecting numerous sea dwelling creatures, as shown by this partially dissolved gastropode shell. (Nina Bednaršek/NOAA)

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The study also showed that the acidification caused during the PETM lasted for 70.000 years.

“It didn’t bounce back right away,” said Timothy Bralower, a researcher at Penn State who was not involved in the study. “It took tens of thousands of years to recover.”

But even this massive process (the PETM) was nowhere near what we are doing now.

“This could be the closest geological analog to modern ocean acidification,” study coauthor Bärbel Hönisch, a paleoceanographer at Columbia, said in a statement. “As massive as it was, it still happened about 10 times more slowly than what we are doing today.”

This acidification will have dramatic effects, and in 100 years, the marine ecosystems might look entirely different from now.

In other words, what we are doing to the planet is unprecedented. It’s not that there wasn’t CO2 in the atmosphere and in the oceans, it’s not that this rise is unprecedented – but the rate at which it is happening is. This is not a natural process, we are causing it. It’s high time we man up and start taking responsibility for this, before the consequences become unbearable.

Journal Reference: Rapid and sustained surface ocean acidification during the Paleocene-Eocene Thermal Maximum. DOI: 10.1002/2014PA002621