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How we unraveled the mystery of a global spike in an ozone-eating gas

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23.05.2019

Since being universally ratified in the 1980s, the Montreal Protocol–the treaty charged with healing the ozone layer–has been wildly successful in causing large reductions in emissions of ozone depleting substances. Along the way, it has also averted a sizeable amount of global warming, as those same substances are also potent greenhouse gases. No wonder the ozone process is often held up as a model of how the international community could work together to tackle climate change.

However, new research we have published with colleagues in Nature shows that global emissions of the second most abundant ozone-depleting gas, CFC-11, have increased globally since 2013, primarily because of increases in emissions from eastern China. Our results strongly suggest a violation of the Montreal Protocol.

A global ban on the production of CFCs has been in force since 2010, due to their central role in depleting the stratospheric ozone layer, which protects us from the sun’s ultraviolet radiation. Since global restrictions on CFC production and use began to bite, atmospheric scientists had become used to seeing steady or accelerating year-on-year declines in their concentration.

Ozone-depleting gases, measured in the lower atmosphere. Decline since the early 1990s is primarily due to the controls on production under the Montreal Protocol. [Image: courtesy of AGAGE/CSIRO]But bucking the long-term trend, a strange signal began to emerge in 2013: The rate of decline of the second most abundant CFC was slowing. Before it was banned, the gas,........

© Fast Company