British Scientists Say Carbon Dioxide Is Turning the Oceans Acidic
The New York Times, July 1, 2005
Whether or not it contributes to global warming, carbon dioxide is turning the oceans acidic, Britain's leading scientific organization warned yesterday.
In a report by a panel of scientists, the organization, the Royal Society, said the growing acidity would be very likely to harm coral reefs and other marine life by the end of the century.
"I think there are very serious issues to be addressed," the panel's chairman, Dr. John Raven of the University of Dundee in Scotland, said in an interview. "It will affect all organisms that have skeletons, shells, hard bits that are made of calcium carbonate."
The 60-page report was timed to influence next week's Group of 8 economic summit meeting. Prime Minister Tony Blair of Britain, president of the group this year, has been calling for strong action to limit climate change.
Unlike forecasts of global warming, which are based on complex and incomplete computer models, the chemistry of carbon dioxide and seawater is simple and straightforward.
The burning of fossil fuels by cars and power plants releases more than 25 billion metric tons of carbon dioxide into the air each year. Roughly a third of that is absorbed by the oceans, where the gas undergoes chemical reactions that produce carbonic acid, which is corrosive to shells.
"That's indisputable," Dr. Raven said. "I don't think anyone can get around that. It's really rock-solid high school chemistry."
The pH scale, which measures the concentration of hydrogen, runs from 1, the most acidic and highest concentration of ions, to 14, the most alkaline, with almost no ions. Ocean water today is somewhat alkaline, at 8.1, about 0.1 lower than at the start of the Industrial Revolution two centuries ago.
But like the magnitude scale of earthquakes, one unit on the pH scale reflects a change of a factor of 10. The 0.1 pH change means there are now 30 percent more hydrogen ions in the water.
Depending on the rate of fossil fuel burning, the pH of ocean water near the surface is expected to drop to 7.7 to 7.9 by 2100, lower than any time in the last 420,000 years, the Royal Society report said.
Dr. Patrick J. Michaels, a senior fellow in environmental studies at the Cato Institute, the libertarian research group based in Washington that is skeptical that global warming will cause serious environmental harm, pointed out that carbon dioxide levels in the atmosphere had been higher for 90 million of the last 100 million years.
But Dr. Ken Caldeira, a research scientist at the Carnegie Institution's Department of Global Ecology in Stanford, Calif., and a member of the Royal Society panel, said the difference was that the current carbon dioxide release was occurring quickly, over just two centuries. In the past, water from the deeper ocean would have had time to mix, diluting the effect of the carbon dioxide. "If we put it out over a few hundred thousand years, we'd have nothing to worry about," he said.
The pH change is likely to slow the rate of growth of coral reefs, which are already suffering from warmer temperatures and pollution, the report said.
"By mid-century, 2050-ish, we will probably see noticeable gaps within coral reefs," Dr. Raven said. "Any weakening of their skeleton can make them more prone to storm events."
The increased acidity could also reduce populations of plankton with calcium carbonate shells, disrupting the food chain and hurting some fisheries, the scientists said.