Oceans today absorb about one-third of the carbon dioxide humans send into the atmosphere, about 22 million tons a day.
This great service, which has substantially slowed global warming, has been accomplished at great cost: The trend in ocean acidification is about 30 times greater than natural variation, and average surface ocean pH, the standard measure of acidity, has dropped by 0.1 unit.
That’s a 25-percent increase in acidity, which is significant.
Higher acidity is damaging many ocean species that use calcium carbonate to form their skeletons and shells. Studies have shown that calcium carbonate formation is disrupted if water becomes too acidic. Ocean acidification also appears to be affecting whole ecosystems, such as coral reefs, which depend on the formation of calcium carbonate to build reef structure, which in turn provides homes for reef organisms.