Ozone recovery back on track

A potent ozone-depleting chemical whose emissions unexpectedly spiked in recent years has quickly dropped back to much lower levels, putting the recovery of the stratospheric ozone layer back on track, according to a new study by scientists at MIT, the University of Bristol, and other institutions in South Korea, the U.S., Japan, Australia, and Switzerland.

The chemical in question is CFC-11, a chlorofluorocarbon that was once commonly used for refrigeration, insulation, and other purposes. When emitted to the atmosphere, CFC-11 can loft into the stratosphere, where the sun’s ultraviolet radiation breaks the chemical down to release chlorine — a noxious chemical that then eats away at ozone, stripping away the Earth’s natural shield against UV rays.

CFC-11 and other chlorofluorocarbons are now banned under the Montreal Protocol, an international treaty under which every country agreed to phase out the chemicals’ production and use by 2010.

But in 2018, a team of scientists reported a concerning spike in global emissions of the chemical beginning in 2013.  In 2019, a second team reported that a significant portion of the emissions could be traced to eastern China, predominately the Shandong and Hebie provinces.

Now, in two papers published in Nature, the same teams report that global annual emissions of CFC-11 into the atmosphere have declined sharply, by about 20,000 U.S. tons, from 2018 to 2019.

The researchers traced a substantial fraction of the global emission reductions to the very same regions of eastern China where they had previously reported the original spike. The results are consistent with evidence that the country has taken successful actions to stamp out illegal production of this ozone-depleting chemical.

Image Credit: KMA/NIMS

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