Earth Equity News

Acidifying Oceans. By J. Madeleine Nash, High Country News, October 16, 2008. "As carbon dioxide rises in the atmosphere, the ocean mops up much of the excess. Over the past two centuries, scientists estimate that its vast blue waters have absorbed something like 40 percent of the carbon dioxide we've thus far emitted. But this assist to the atmosphere comes at a price. In water, carbon dioxide turns into carbonic acid... During the PETM [55 million years ago] the ocean contained enough carbonic acid to make life difficult for many shell-building organisms... Today, the ocean is already less alkaline than in pre-industrial times, by about 0.1 units of pH. Some 55 million years ago, the pH shift was more extreme, in the neighborhood of 0.4 units. But, says Zachos, we are now on track to surpass that shift by the start of the next century and to double it by the year 2300... More than anything, it's the rate of change that has scientists worried... It's one thing to add a big load of carbon dioxide to the ocean over a few millennia, quite another to shock the ocean by adding a similar amount in just a few centuries. 'We do not know with certainty what the consequences will be,' says Ken Caldeira, a climate expert with the Carnegie Institution Department of Global Ecology at Stanford University. 'But we are now adding carbon so fast that, chances are, the disturbance to the ocean will be even more extreme [than in the PETM].'"