In the 1970s, scientists discovered that freons reacted with ozone in the atmosphere, creating an ozone hole . Following an international agreement in 1989, the use of freons dropped drastically and the hole began to shrink. But then surveys in 2014 showed that emissions of freon surprisingly increased again .
It was about the substance fluorotrichloromethane, also called freon 11, which unexpectedly went up. Freon 11 can be used as a coolant, but stopped being used as early as the 1990s in most countries.
After a detective work, researchers managed to show that much of the emissions came from the illegal use of freon 11 among industries in eastern China. As the emissions came from a relatively limited area, it was relatively easy to address much of the problem when the Chinese government put its foot down.
This has now resulted in a clear reduction in freon 11 emissions, according to two separate studies from research groups in the USA and South Korea. One group studied emissions from the area in China. It turned out that emissions here have decreased from 15,000 tonnes in 2017 to 5,000 tonnes in 2019 .
The second research group examined the global emissions of freon 11. Their research shows that the total emissions have fallen from an average of 69,000 tonnes in 2014–2018 to 52,000 tonnes in 2019 . This is the same level as the emissions were before 2013.
Now China did not account for the entire increase in illegal emissions, and finding out where the rest comes from will be the next challenge for researchers. By continuing to monitor and continuously reduce emissions, researchers believe that the ozone hole will have fully recovered in 50 years.