The mystery source behind the continued emissions of an already-banned ozone-depleting substance is finally discovered. Instead of declining after the ban, emissions are even found to have increased in certain regions.

Ozone-Depleting Emissions

It was in 2010 that the production of carbon tetrachloride was banned worldwide because of its destructive properties on the Earth’s ozone layer, which protects us from harmful ultraviolet radiation. However, recent studies revealed that despite the ban, there are still about 40,000 tons of the substance still being emitted into the atmosphere every year.

The source of the emissions was a mystery to scientists, so researchers from the University of Bristol, along with researchers from the United States, South Korea, Switzerland, and Australia collaborated to quantify the emissions in East Asia using both ground-based and airborne atmospheric concentration data from 2010 to 2016.

Mystery Source Revealed

What researchers found was that there are still ongoing significant emissions coming from eastern China which accounts for a large sum of the missing global estimates. In addition, the carbon tetrachloride emissions from east Asia were even found to be significantly larger than previously thought.

Furthermore, they also found no evidence of decrease in emissions in the region since 2010. In fact, the data even shows a slight increase in emissions from the region since 2010, as well as a new source of emissions from Shandong province in China after 2012.

Gaps In Knowledge

Coauthor Dr. Matt Rigby notes that while their research answers a big question, there are still gaps in knowledge that need to be addressed, such as the exact industries that are responsible. In addition, it is still unknown whether the emissions were produced intentionally or inadvertently, perhaps as a byproduct of producing other chemicals such as chlorine.

“Studies such as this show the importance of continued monitoring of ozone-depleting gases. There is a temptation to see ozone depletion as a problem that has been solved. But the monitoring of man-made ozone-depleting gases in the atmosphere is essential to ensure the continued success of the phase-out of these compounds,” said lead author Dr. Mark Lunt of the University of Bristol.

The study is published in Geophysical Research Letters.

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