The gas trichlorofluoromethane contributes to the depletion of the ozone layer, which is why its emission has been banned worldwide since 2010. Nevertheless, a few years ago monitoring networks registered a renewed increase in this “ozone killer”. However, after the source was located in China in 2017 and the authorities were informed, there is now good news: Since then, CFC-11 emissions have fallen dramatically again, as researchers are now reporting.
The emission of trichlorofluoromethane (CFC-11) was banned worldwide in 2010 as part of the Montreal Protocol, because the substance previously used as a refrigerant and propellant is considered an “ozone killer”. In the polar atmosphere it releases chlorine radicals and thus contributes to the depletion of the ozone layer. However, despite the ban, CFC-11 emissions have increased since 2013. Air measurements and further research showed that in northeast China from 2012 to 2019 up to 100,000 tons of the ozone-depleting compound were released during the production of insulating foams. The Chinese authorities have been informed and they say there have been arrests, material seizures and the demolition of production facilities.
Did it do anything?
Two international research teams around Sunyoung Park from the Kyungpook National University in South Korea and around Stephen Montzka from the US National Oceanic and Atmospheric Administration (NOAA) have now examined whether this actually reduces the emissions of trichlorofluoromethane. They first investigated whether emissions have changed at regional level in the Chinese provinces of Shandong and Hebei. To do this, they compared the CFC-11 concentrations determined by Korean and Japanese measuring stations with computer models that simulate the transport of CFC-11 through the global atmosphere. The teams also checked the global data with the help of another computer model. This calculates the change in emissions that is required to match the observed global CFC-11 concentrations.
It was found that CFC-11 emissions have decreased dramatically. Overall, they fell by around 10,000 tons annually between 2017 and 2019, both on a regional and global level. The researchers estimate that the decline is comparable to or even greater than the original increase between 2012 and 2017. “The results are very welcome news and will hopefully mark the end of a troubling period of obvious violations,” said co-author Luke Western of the University of Bristol. “If emissions had stayed at the significantly increased levels we found two years ago, the recovery of the ozone layer might have been delayed by many years. Since CFC-11 is also a strong greenhouse gas, the illegal emissions contributed to climate change to an extent that is comparable to the CO2 emissions of a city with a population of over a million, ”emphasizes the researcher.
Monitoring network is being expanded
“The new analyzes show how important an independent review of international environmental agreements is,” explains Stefan Reimann from the Eidgenössische Materialprüfungs- und Forschungsanstalt (Empa). “Without air measurements in this special region of the world, it would not have been possible to determine the regional emissions.” The problem: The previous measurement networks are incomplete and do not yet cover large parts of the world, so that it cannot be ruled out that there will be more globally Sources of climate-damaging gases. The first measures to identify, localize and quantify unexpected emissions of controlled substances have now been taken by representatives of the Montreal Protocol: They expanded the atmospheric measurements in key regions of the world.
“This method of emission control could also prove to be very helpful if, in the not too distant future, several countries have to drastically reduce their greenhouse gas emissions due to their obligations under the Paris Agreement,” speculates Reimann’s colleague Stephan Henne. Scientists are currently working intensively on observation and modeling systems that enable independent emission estimates for the most important greenhouse gases at the country level and thus promote mutual trust between the signatory states, the researcher concluded.
Source: Federal Materials Testing and Research Institute, specialist article: Nature, doi: 10.1038 / s41586-021-03260-5; doi: 10.1038 / s41586-021-03277-w