Last year marked 30 years since the Montreal Protocol, an international agreement signed by 197 countries aimed at healing the ozone layer. Heralded as a landmark environmental treaty 鈥� the first in UN history to achieve universal 鈥� its effectiveness has been a beacon for international progress on so-called .
But there has been a surprising rise in emissions of one of the most damaging ozone-depleting chemicals banned by the treaty, a new study has found. Its apparent source: east Asia.
A gaseous shield in the stratosphere, the ozone layer protects us from harmful effects of the sun鈥檚 ultraviolet-B radiation, including skin cancer, cataracts and a compromised immune system. Since global bans were introduced, levels of trichlorofluoromethane (CFC-11) in the atmosphere have been steadily declining. Air concentrations of this chemical, sampled with high precision at 12 remote sites around the globe, fell at a constant rate between 2002 and 2012. But now a sudden slowdown of that decline 鈥� by as much as 50 per cent 鈥� has been detected.
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鈥淭his is the most surprising and unexpected finding of my career鈥�, says Stephen Montzka at the US National Oceanic and Atmospheric Administration, who led the study. For 27 years, Montzka has been monitoring multiple atmospheric measurements taken every day.
Like atmosphere detectives, Montzka and colleagues used 3D modelling to identify the source of the new emissions. They discovered that natural causes could not explain the magnitude of the observed change. They also investigated whether the new emissions source could be down to old stores of CFC-11 鈥� for example, released from foams when old buildings are destroyed. The extent of the concentration change made that improbable too.
The team concluded that only one possibility remained: CFC-11 was being newly created. A revival of intentional CFC-11 production for use in foams is unlikely, says Montzka, given that alternatives have been used for many years.
But, with lots of global production of fluorinated and chlorinated methanes like the less damaging HCFC-22 鈥� the starting material for Teflon and, until recently, used as a refrigerant in air conditioners 鈥� these industrial processes could produce CFC-11 as a by-product and may be knowingly or unknowingly emitting it.
Exactly what鈥檚 going on remains a mystery, but in publishing this data, Montzka hopes to get a broader community to help investigate.
That鈥檚 already begun, and the team鈥檚 resultshave been independently verified. 鈥淲e鈥檙e partly kicking ourselves for not having noticed it before [Montzka] did,鈥� says Ray Weiss, who oversees complementary but independent monitoring at the Advanced Global Atmospheric Gases Experiment (AGAGE).
As for the location of this apparently fugitive CFC-11 source, a study of wind patterns at air sampling locations points the finger at eastern Asia.
At a time when global environmental challenges are multiplying, this is a wake-up call. 鈥淚t indicates you cannot just trust countries to adhere to regulations and international treaties,鈥� says Michaela Hegglin at the University of Reading. This does not bode well for another wicked problem: carbon dioxide emissions.
It shows that constant vigilance is required. By slowing emissions of ozone-destroying chemicals that are also potent greenhouse gases, the Montreal Protocol has been a double-whammy success. But these new emissions, plus worries about a new generation of chemicals, now cast doubt on environmental progress.
The good news is that monitoring works. Countries can restrict information on production and falsify numbers, but ultimately, what gets emitted will reach sensors. As Montzka says, the atmosphere doesn鈥檛 lie. So keeping a careful watch remains critical if we are to catch cheats and ensure that ozone layer restoration continues.
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