Banned ozone-destroying gas may still be in production

Earth and the Sun

If the source of these emissions can be identified and mitigated soon, the damage to the ozone layer should be minor.

This treaty saw the production of CFCs, including CFC-11, banned in developed countries in the mid 1990s and in the rest of the world by 2010.

Last fall, it was reported that the hole in the Earth's ozone layer had shrunk to its smallest size since 1988, which was great news.

The findings, published in the journal Nature, show that since 2012, the rate of decline for a substance known as CFC-11 has slowed, and Montzka's research suggests new emission sources may have popped up over East Asia.

"We're raising a flag to the global community to say, 'This is what's going on, and it is taking us away from timely recovery from ozone depletion, '" said NOAA scientist Stephen Montzka, lead author of the paper, which has co-authors from CIRES, the United Kingdom, and the Netherlands.

"Emissions today are about the same as it was almost 20 years ago".

Another key question is whether there could be another explanation for a slower decline in CFC-11 post-2012, such as a change in the rate of chemical processes such as UV photolysis that break down CFC-11 in the stratosphere, or an increase in emissions from CFC "banks" - reservoirs that persist in old equipment and products that are still in use. But the data just didn't match up.

"In the end, we concluded that it's most likely that someone may be producing the CFC-11 that's escaping to the atmosphere", said Montzka. "We know of no production even for intermediary or side products".

These could hamper the recovery of the ozone hole and worsen climate change.

"The ozone layer remains on track to recovery by mid-century", the U.N. Environment Program (UNEP) said in a statement, reacting to the findings.

Exploring further, the researchers found the concentration of CFC-11 to be unusually high in the Northern Hemisphere.

"This evidence strongly suggests increased CFC-11 emissions from eastern Asia after 2012".

They were also used as propellants in aerosol sprays and in solvents.

So where exactly are these increased emissions coming from? A US observatory in Hawaii found CFC-11 mixed in with other gases that were characteristic of a source coming from somewhere in east Asia, but scientists could not narrow the source down any further. I think this will be quite a shock to many people who, like me, thought the Montreal Protocol was working well'.

Unreported production of CFC-11 outside of certain specific carve-out purposes in the treaty would be a "violation of global law", Weller confirmed, though he said that the Protocol is "non-punitive" and the remedy would probably involve a negotiation with the offending party, or country. "There's a reasonable chance we'll figure out what's happening here", he said.

However, it took many decades for scientists to discover that when CFCs break down in the atmosphere, they release chlorine atoms that are able to rapidly destroy ozone molecules.

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