A lot of the carbon dioxide spewed out of our power plants, factories, and cars is absorbed by our oceans. Those oceans, in turn, are growing increasingly acidic. Parts of our oceans have already become acidic enough that some sea snails' shells are dissolving as soon as they're born. Other sea creatures, like coral, appear to be facing an existential threat, too. Now, new science shows that if the past is any guide, the process is just getting started—it's going to get a lot worse, and fast.
In fact, the destabilizing, extinction-driving process seems to be happening ten times faster than the last major carbon-driven ocean acidification event, when marine acidity rose 100 percent in the span of few thousand years—and stayed that way for another 70,000. This new research, from a crew of Columbia, Yale, and UC Santa Cruz paleoceanographers who analyzed sea floor sediments drilled off the coast of Japan—shows that during the last period of comparable global warming, ocean acidification soared, and reshaped and wreaked havoc on marine ecosystems.
Scientists—paleoclimatologists, especially—often look to a climate event called the Paleocene-Eocene Thermal Maximum (PETM), which occurred 56-58 million years ago, to draw corollaries to modern day global warming. That was the last time when such a huge amount of carbon was loosed (for reasons still unknown) into the atmosphere and oceans. Columbia University's Lamont-Doherty Earth Observatory explains what the scientists uncovered about the impact the PETM carbon boom had on the oceans in its release:
In the oceans, carbonate sediments dissolved, some organisms went extinct and others evolved. Scientists have long suspected that ocean acidification caused the crisis—similar to today, as manmade CO2 combines with seawater to change its chemistry. Now, for the first time, scientists have quantified the extent of surface acidification from those ancient days, and the news is not good: the oceans are on track to acidify at least as much as they did then, only at a much faster rate.
“This could be the closest geological analog to modern ocean acidification,” study coauthor Bärbel Hönisch, a paleoceanographer at Columbia, said in a statement. “As massive as it was, it still happened about 10 times more slowly than what we are doing today.” I followed up to confirm the comment, and Hönisch replied by email:
"The acidity of seawater is measured by its concentration of hydrogen ions," Hönisch wrote. "This concentration has increased by ~25% since the onset of industrialization, and it is projected to increase by another ~75% by the end of the century. This means that the hydrogen ion concentration will have doubled by the year 2100 compared to preindustrial times. Of course, all this depends on how much CO2 we keep adding to the atmosphere. These estimates are based on a business-as-usual scenario."
In other words, we're looking at a 100 percent increase in ocean acidity over the course of a few hundred years—and a 75 percent rise in acidity over the course of a matter of decades. This is happening as a direct result of humankind's penchant for pumping carbon into the atmosphere in increasingly epic proportions. Previous studies have suggested that the rate of ocean acidification we're currently seeing is "unprecedented," and that certainly seems to be the case.
As the scientists note, that means many organisms will go extinct, some others will evolve—and the entire marine ecosystem will likely look very different three hundred years from now.