A mysterious surge in emissions of an illegal ozone-destroying chemical has been tracked down to plastic foam manufacturers in China, according to an on-the-ground investigation published on Monday.

The chemical, trichlorofluoromethane or CFC-11, has been banned around the world since 2010 and is a potent destroyer of ozone, which protects life on Earth from UV radiation, and strong greenhouse gas. A shock rise in the gas in recent years was revealed by atmospheric scientists in May, but they could only narrow the source to somewhere in East Asia.

The Environmental Investigation Agency, a non-governmental organisation, has now identified widespread use of CFC-11 factories in China that make insulating foams. The EIA’s investigators identified factories that sold the chemicals needed for foam-making, then contacted and visited them.

“We were dumbfounded when out of 21 companies, 18 of them across China confirmed use of CFC-11, while acknowledging the illegality and being very blase about its use,” said Avipsa Mahapatra at the EIA. Furthermore, the companies said the use of CFC-11 was rife in the sector. “It was very clear. These companies, again and again, told us everybody else does this,” she said.

A blockbuster study published in the journal Nature yesterday (May 16) revealed that for the first time since the 1980s, ozone-depleting chlorofluorocarbons (CFCs) have ticked sharply upward in the atmosphere — suggesting a new source. Here's the thing though: Not only do scientists have no idea what that new source is, it doesn't make much sense that someone would decide to pump out CFCs again. That's because there are numerous, inexpensive alternatives to CFCs that work just as well.

As The Washington Post explained in its detailed report on the study, global CFC production has been near zero since the materials were banned in the 1987 Montreal Protocol. Overall, atmospheric CFCs are still declining, and the ozone layer is still replenishing itself. But the new source has slowed that process significantly, and scientists find the situation completely baffling, said John L. Ferry, an environmental chemist at the University of South Carolina.

Air conditioners are installed in most of the homes and cars to keep the inner environment cool and comfortable. Air conditioner is one of the main reasons for global warming as it tends to release harmful emissions into the atmosphere.