The ocean is releasing ozone-depleting gases at a faster rate due to rising global temperatures, prompting scientists to warn of more ultraviolet radiation and a greater cancer risk.
Chlorofluorocarbons, or CFCs, have slowly collected in deep ocean water for decades. The human-produced gas, commonly used for manufacturing aerosol sprays and refrigerants, is released into the atmosphere and then sucked into the ocean from surface wind, according to a new study published in the Proceedings of the National Academy of Sciences.
But the world’s oceans are on pace to reverse their role as a sink for CFCs, and researchers say hotter ocean temperatures due to climate change will make it happen faster.
As gases such as CFCs degrade the stratospheric ozone layer, the Earth’s surface loses its protection against ultraviolet rays. Scientists warn that increased exposure to UVB rays causes increased risk of cancer, cataracts and immune deficiency disorders.
Since 2010, the Montreal Protocol—a global agreement to protect the stratosphere ozone layer by phasing out the production and consumption of ozone-depleting substances—has cut CFC emissions. Those already absorbed by the ocean are starting to be emitted as the atmosphere’s levels dip.
But warmer water weakens oceans’ ability to be a reservoir for the potent ozone-consuming gas. Without climate change, the researchers predict that by 2075 oceans will emit more CFCs than they absorb. That shift could happen up to 10 years earlier with climate change.
“Even if there were no climate change, as CFCs decay in the atmosphere, eventually the ocean has too much relative to the atmosphere, and it will come back out,” said Susan Solomon, co-author and professor at the Massachusetts Institute of Technology. “Climate change, we think, will make that happen even sooner. But the switch is not dependent on climate change.”
They also predict that this shift would happen first in the Northern Hemisphere—circulation there is expected to slow down, which leaves more gases in shallow waters, making it easier to escape into the atmosphere.
Peidong Wang, co-author and graduate student at MIT, added that climate change also can cause especially harmful CFCs, like CFC-11—a Class 1 ozone-depleting substance, according to EPA—to linger in the atmosphere longer, too.
“CFC-11 also has a very long life in the stratosphere where it depletes the ozone—up to 55 years. CFC-12 can live up to 95 years,”; Wang added. “It can only be destroyed when it reaches high into the stratosphere, which takes awhile, meaning that CFCs are lasting longer in the atmosphere.”
Prior to this, Wang said that many CFC detection models were pinning ocean CFC emissions on some countries near large ocean emission areas. From their estimates, he said current models have overpredicted illicit CFC-11 emissions by 10%.
Their findings could change policy around the Montreal Protocol, since many countries may not actually be violating the agreement.
“We know that some areas are actually producing CFCs illegally, like in the Shandong province in China,” he said. “People might think these extra emissions are still coming from these countries, but it could just be increased emissions from the ocean.”;
Wang said to decrease CFCs in the atmosphere, new policies need to look toward the land, not the sea. The amount of CFCs in the ocean is about 10% compared with CFCs stored on land. To prevent CFCs from getting into the air or water, he said scientists need to focus on developing technology that keeps land-based CFCs from escaping.
“It will be too technologically difficult to scrub CFCs from the oceans,”; he said. “CFCs are stored in chillers and building insulating foams, so when we tear down old buildings, that’s when new CFCs are released.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2021. E&E News provides essential news for energy and environment professionals.
Scientific American Content: Global