China is going back to fighting the ozone hole.

Nature reports on Chinese officials having a redo on one of our past environmental successes, seeking out the source of massive plumes of ozone-destroying CFCs detected over two Chinese provinces:

Now the government is under pressure to act — and has presented a plan to help it track and reduce emissions of the chemical, known as trichlorofluoromethane or CFC-11. Measures include establishing a national monitoring network to track ozone-depleting chemicals, along with heftier penalties for companies caught illegally producing the chemical.

The “document sets the stage for real progress on this important issue”, says David Fahey, director of the Chemical Sciences Division at the US National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory in Boulder, Colorado.

The Chinese environment ministry disputes that there is enough evidence to pin the recently discovered spike in emissions on China, but agrees that more data are needed to understand the problem. The ministry was “shocked and perplexed” when it heard of rising levels of the chemicals, a spokesperson told Nature’s news team.

CFC-11 was once a popular refrigerant, and widely used to produce polyurethane foam insulation. But the 1987 Montreal Protocol, a legally binding global treaty to protect the ozone layer, called for its production and trade to be phased out by 2010. .

The treaty worked, and global CFC-11 production dropped until 2013, when a surprising slowdown in that decline suggested that there was a new source of emissions.

The studies that pointed to China as the source of the mysterious spike1,2 used data from monitoring stations in Japan and South Korea to trace the gas to the provinces of Hebei and Shandong — but no more precisely.

Scientists suspect that factories there might have resumed production of a CFC-11-based foam insulator. Because China has ratified the Montreal Protocol, it is obliged to address any illegal CFC-11 production.

The Chinese government acknowledges some illegal CFC-11 production: before the meeting, it provided the multilateral fund with a report detailing how it had seized 114 tonnes of illegally produced CFC-11 since 2012.

But such amounts could not account for the roughly 7,000 tonnes of CFC-11 that, according to estimates in the May Nature paper, is being newly produced each year.

You can read more about the May detection of CFC-11 here.