Oceans have acidified more in the last 200 years ‘than they did in the previous 21,000 years’

Man-made carbon emissions have acidified the world’s oceans far beyond their natural levels, new research suggests.

In some regions, acidity levels rose faster in the last two centuries than it did in the previous 21,000 years, a study from the University of Hawaii has shown.

Ocean acidity makes it harder for organisms such as molluscs and coral to construct the protective layers they need to survive.

Scientists looked at changes in the saturation level of aragonite, a form of calcium carbonate used to measure ocean acidification.

As seawater acidity rises, the saturation level of aragonite falls.

Direct observations only date back 30 years, which is not long enough to reveal a meaningful trend.

However the new research used simulations of ocean and climate conditions going back 21,000 years to the Last Glacial Maximum and forward in time to the end of the 21st century.

In several key coral reef regions aragonite saturation is already five times below its lowest pre-industrial range, according to the model.

This translates to a decrease in overall calcification rates of corals and other shell-forming organisms of 15%, scientists at the university believe.

Daily Mail, 23 January 2012. Full article.

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