Ocean acidification, that other big CO2 problem, is likely going to be even harder to stave off than global warming. The oceans respond more slowly to climatic changes than the atmosphere, meaning that the massive amounts of carbon dioxide the seas continue to absorb are going to make themselves known over the coming years, whether we like it or not.

As Oregon State oceanographer Burke Hales told Eric Scigliano for his recent OnEarth story about oysters and acidification: "We’ve mailed a package to ourselves, and it’s hard to call off delivery."

Indeed, a study published yesterday in the journal Nature Climate Change suggests we have already had a huge impact on ocean acidity. The study, led by Tobias Friedrich of the International Pacific Research Center in Hawaii, found that the rates of acidification currently exceed the expected natural variation by 30 times.

"In some regions, the man-made rate of change in ocean acidity since the Industrial Revolution is hundred times greater than the natural rate of change between the Last Glacial Maximum and pre-industrial times," Friedrich said in a press release. The glacial maximum occurred more than 20,000 years ago, and the oceans acidified naturally in the millennia following. Even then, though, the rates of acidification were two orders of magnitude smaller than what we see today.

Acidification, or a decrease in pH of ocean water, is already starting to affect marine life. Oysters and other shellfish are particularly at risk, as are coral reefs and all the species that rely on them for habitat. According to the new study, the conditions that allow coral reefs to grow will be available in only five percent of the oceans by 2100. Today that number is 50 percent.

Image: thinkpanama/Flickr