As oceans become more acidic by soaking up carbon dioxide released into the atmosphere, they will produce less of a gas that protects the Earth from the sun's radiation and will amplify global warming, according to a new study from a team of German researchers.
It is a widely held belief that carbon dioxide emissions contribute to global warming, and that oceans lessen the effects of those emissions by absorbing a large amount of carbon dioxide. But the study, released on Monday, says past research has not linked climate change and ocean acidification.
Scientists at the Max Planck Institute for Meteorology in Germany found that concentrations of the compound dimethyl sulfide (DMS), which produces the gas that helps cool the Earth's surface, were significantly lower in waters with higher levels of acidity. The lower a solution's pH level is, the more acidic it is considered.
Over the last 200 years, oceans have absorbed about 525 billion tons, roughly 50 percent of human-released carbon dioxide emissions.
"The 'price' for storing [carbon dioxide] is an ongoing decrease of seawater pH, a process that is likely to have diverse and harmful impacts on marine biota, food webs, and ecosystems," the study says.
Changes in the acidity of oceans, and thus the amount of DMS they produce, have the potential "to notably alter the Earth's radiation budget," the study says.
Historically, sea water has had a pH level of around 8.16, but has fallen by about 0.1 units since the beginning of the Industrial Revolution, to 8.05, according to the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory.
Although that sounds like a small change, it represents a nearly 30 percent increase in acidity, according to the Center for Ocean Solutions, located in Monterey, Calif. Oceans have not seen a change so "abrupt and large" for at least 650,000 years, the center says. Research predicts that sea water pH levels may continue to decrease by as much as 0.4 units by 2100.
And that's also a problem because higher acidity levels will adversely affect different ocean species that many people rely on for food and jobs, such as oysters, clams, sea urchins and deep sea corals, according to NOAA.
"Today, more than a billion people worldwide rely on food from the ocean as their primary source of protein," NOAA's Pacific Marine Environmental Laboratory says. "Many jobs and economies in the U.S. and around the world depend on the fish and shellfish in our oceans."