Fifty-five million years ago, Earth endured a period of rapid global warming, a shift so dramatic it altered ocean and atmospheric circulation, driving plankton in the seas and mammals on land to extinction.
The event, called the Paleocene-Eocene Thermal Maximum, may have been caused by volcanic eruptions that flooded the atmosphere with billions of tons of carbon dioxide. Or, methane gas frozen beneath the sea on continental shelves could have destabilized, diffusing into the atmosphere where it was oxidized into carbon dioxide.
As the oceans absorbed much of the carbon dioxide, their pH fell and they grew increasingly acidified.
Thirty percent to 40 percent of a major class of plankton, called foraminifera, went extinct.
Today, scientists look at that turn in Earth’s history with worry. Rising carbon dioxide emitted by the burning of gas, oil and other fossil fuels is being absorbed by the oceans – making them increasingly acidified once again.
Every day, about 22 million tons of carbon dioxide generated from human activities – primarily from the burning of fossil fuels – are entering the world’s oceans. That’s 10 times the rate at which carbon dioxide would be absorbed by the oceans if humans did not burn fossil fuels.
The Paramus Post, 24 September 2006- Article
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