Atmospheric readings show that someone, somewhere, isn’t playing by the rules.


Aerosol used to widely incorporate these dangerous chemicals.
Image credits PiccoloNamek / Wikimedia.

Just last November, I’ve had the pleasure to report that, according to NASA’s measurements, 30 years of international effort and cooperation were doing the ozone layer some good. It was, all in all, very good news: it showed states could successfully and sensibly work together on ecological problems, and it meant we won’t get fried by solar radiation — both wins in my book.

However, a new study shows that not all is as well as we thought: someone has been cheating on the Montreal Protocol by producing new ozone-depleting chemicals on an industrial scale.

The ozone hole, renewed?

The Montreal Protocol of 1987 banned the production of three main ozone-destroying classes of chemicals: chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Since these compounds take an impressively long time to break down in the atmosphere, monitoring systems were set in place to make sure everything went smoothly. And good thing they did.

A team of researchers led by Stephen Montzka of the US National Oceanic and Atmospheric Administration (NOAA) reports that something is off with CFC-11 levels in the atmosphere. This chemical — previously used as a solvent, a refrigerant, as a precursor in styrofoam production, and a propellant in spray cans — is currently banned for production under the protocol. We used to employ a lot of it, however, and there are still sources of this gas leaking into the atmosphere (such as old refrigerators in landfills). However, these secondary sources should gradually decline, then disappear completely. As they do, we should see the decline of CFC-11 levels in the atmosphere accelerate.

But we aren’t. CFC-11 levels dropped some 2.1 ppt (parts-per-trillion) each year between 2002 and 2012. Afterward, however, the decline actually started to slow down: between 2015 and 2017, CFC-11 levels in the atmosphere dropped by only 1.0 ppt per year.

The concentration of CFC-11 in the Northern (red) and Southern (blue) Hemispheres compared to projected decline (gray lines).
Image credits Montzaka et al. (2018), Nature.

First, the team checked whether the change could come from natural processes. Some of these, however, could be ruled out quite easily: the first was whether weather-pattern-induced movements of CFCs in the stratosphere caused the observed variations. Another possible explanation, that a lot of old buildings using CFC-11-based ventilation systems were demolished at the same time, was also ruled out, as it didn’t plausibly fit the data, according to the team.

The team used atmospheric modeling to analyze what effect could lead to the observed rise. The concentration of these gases has always been higher in the (more developed, more industrialized) Northern Hemisphere than in the Southern one. Over the last few years, the team reports, this discrepancy between the two hemispheres has become more pronounced. Other gases haven’t followed the same pattern, the authors add, suggesting that the increase in CFC-11 emissions come from somewhere in the Northern Hemisphere.

Measurements taken at the Mauna Loa observatory in Hawaii also show that CFC-11 isn’t the only anthropic pollutant that’s seeing an uptick roughly since the year 2000. The team’s models showed that natural variability in atmospheric circulation (aka weather patterns) could only explain half of the observed increase — meaning that the only plausible explanation is an increase in emissions.

The team report that the source is most likely somewhere in Eastern Asia. They also estimate that around 6,500 to 13,000 tons of new CFC emissions would fit the observed trend in atmospheric concentrations.

“This is the first time that emissions of one of the three most abundant, long-lived CFCs have increased for a sustained period since production controls took effect in the late 1980s,” the researchers write.

“A delay in ozone recovery […] is anticipated, with an overall importance depending on the trajectory of CFC-11 emissions and concentrations in the future.”

The emissions are a direct violation of the Montreal Protocol. Signatories have taken it upon themselves to monitor CFC production and report it back to the United Nation group which oversees the protocol’s implementation. Against this backdrop, the team was very careful to spell out that they don’t have enough data to point towards a specific nation. They also add that its possible such production is taking place beyond the local government’s back — putting the ball in their court to safeguard the ozone layer.

The paper “An unexpected and persistent increase in global emissions of ozone-depleting CFC-11” has been published in the journal Nature.

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