Two additional regions in Asia were sources of banned ozone-depleting chemicals

A follow-up investigation by NOAA scientists into the sudden increase in emissions of an ozone-destroying chemical between 2010 and 2018 has determined that three regions in Asia – not just one – were responsible for the increased emissions of the banned chemical.

In an article published in the journal Chemistry and physics of the atmosphereanalysis of air samples, including those taken during two major airborne research campaigns, confirmed the increase in CFC-11 emissions from eastern China, but also found a significant increase in emissions from temperate western Asia and tropical Asia.

Lead author Lei Hu, a RAINCOATS scientist who studies CFCs and other ozone-depleting trace gases work at NOAA Global Monitoring Laboratorysaid his team had analyzed a large number of high-quality and well-distributed air samples collected by the scientific community during this period.

New research from the Global Monitoring Laboratory has identified temperate West Asia and tropical Asia as two additional source regions for increased CFC-11 emissions identified by NOAA scientists in 2018. identify China as a source location. Credit: Global Surveillance Laboratory

“Once we analyzed NOAA measurement data from samples collected around the world and at different altitudes in the atmosphere, we were able to explain most of the observed increase in emissions,” said Hu said.

The triumph of engineering has become a global plague

Chlorofluorocarbons, or CFCs, were once considered a triumph of modern chemistry. Stable and versatile, these chemicals have been used in hundreds of products, from military systems to the ubiquitous hairspray spray.

In 1987, NOAA scientists were part of an international team that proved that this family of amazing chemicals damaged the Earth’s protective ozone layer and created the giant hole in the ozone layer that forms every year over Antarctica. The Montreal Protocol, signed later that year, committed the global community to phase out their production. Production of the second most abundant CFC, CFC-11, would cease completely by 2010. Except that is not the case.

Years of vigilance yielded an unwelcome discovery

In 2018, Hu’s colleague Stephen Montzka published an article in the journal Nature who shook the scientific world by describing what turned out to be the first known violation of the Montreal Protocol ban on the production and use of CFC-11. Based on analysis of data collected from the Global Monitoring Laboratory’s worldwide network of sampling sites, scientists were able to demonstrate that CFC-11 emissions had mysteriously increased by 25%, suggesting the presence of a new production in violation of protocol.

Montzka and his NOAA colleagues contributed to a accompanying study led by scientists with Advanced Global Atmospheric Gas Experiment (AGAGE) and published in 2019, which determined that at least 40-60% of the increase in global CFC-11 emissions came from eastern mainland China. However, it is still unclear where the rest of the increase in emissions came from.


This map depicts the flight paths of NASA’s DC-8 Flight Laboratory during the 2016-2018 Atmospheric Tomography mission. Atmospheric measurements collected during the flight allowed NOAA researchers to identify two regions of Asia as contributing to the increase in CFC-11 emissions between 2011 and 2017. Credit: NOAA Chemical Sciences Laboratory

Aerial sampling campaigns were key to new discoveries

In this new work, augmenting NOAA’s ongoing Earth surface sampling network with measurements from both short-term airborne campaigns, Atom and HIPPOPOTAMUSWith NOAA’s continuous in situ atmospheric measurements and regular aircraft profiling, the researchers were able to improve their ability to quantify emissions on a regional to continental scale, particularly from Asia.

With additional data, time, and help from NOAA HYSPLIT atmospheric transport model, which allowed scientists to track air movements over time and identify upwind source regions, Hu’s research team from the Global Monitoring and Chemical Sciences Laboratories was able to assign almost all of the increase in emissions from 2012 to 2017 to the three regions of Asia.

Amplifying the sampling array would improve the accuracy of source identification

Despite the success in detecting increased CFC emissions, there are still significant uncertainties in the regional and continental emission estimates obtained by the researchers, as significant gaps remain in global sampling networks, said Mr. .Hu.

These sampling discrepancies mean that scientists could have difficulty identifying the sources of any future unexpected increases in global CFC emissions, the changes could go unattributed, making it more difficult to recover the climate layer in time. ozone.

Additional sampling locations and frequency, particularly downwind of undersampled regions such as Asia, Africa and South America, would improve scientists’ understanding of changes in global atmospheric composition and make mitigating associated impacts on the ozone layer and climate more quickly, effectively and efficiently.

On the other hand, failure to fill large sampling gaps means that future unexpected global changes may go unattributed, making it more difficult to recover the ozone layer over time.]

This research was funded by NOAA, NASA and the National Science Foundation, with support from CIRES.

For more information, contact Theo Stein, NOAA Communications at [email protected]