Wherever these CFC banks reside, we should consider recovering and destroying them as responsibly as we can
Old equipment such as building insulation foam, refrigerators, cooling systems, and foam insulation are still leaking ozone-destroying gases into the atmosphere, scientists have said.
Researchers have found "unexpectedly high" levels of man-made chemicals known as CFC-11 and CFC-12, which belong to a group compounds responsible for creating a hole in Earth's ozone layer known as chlorofluorocarbons (CFCs), despite a worldwide ban on the production of these gases.
The team from the Massachusetts Institute of Technology (MIT) in the US traced the source of these CFCs to "large banks" of old equipment which were manufactured before the global phase-out, which began in 2000.
They said their findings, published in the journal Nature Communications, contradict previous analysis that these banks would be too small to cause significant damage to the Earth's protective ozone layer.
High in the atmosphere, the ozone shields the planet from harmful ultraviolet rays that can cause problems such as skin cancer and crop damage.
In 1987, countries around the world agreed in the Montreal Protocol to phase out CFCs.
The effect of the phase-out was observed in 2016, when scientists noticed the first signs of healing in the Antarctic ozone layer.
Based on these efforts, a United Nations report in 2018 predicted the upper ozone layer above the Northern Hemisphere would be completely repaired in the 2030s, while the Antarctic ozone hole should disappear in the 2060s.
But MIT researchers said that, if left unchecked, these banks, which are slowly leaking the CFC-11 and CFC-12 gases into the atmosphere, would delay the recovery of the ozone hole by six years and add the equivalent of nine billion metric tonnes of carbon dioxide to the atmosphere.
Susan Solomon, a professor of environmental studies at MIT, and a co-author on the study, said: "Wherever these CFC banks reside, we should consider recovering and destroying them as responsibly as we can.
"Some banks are easier to destroy than others. For instance, before you tear a building down, you can take careful measures to recover the insulation foam and bury it in a landfill, helping the ozone layer recover faster and perhaps taking off a chunk of global warming as a gift to the planet."
The team also found high levels of another ozone-depleting chemical, CFC-113, which is being emitted into the atmosphere at a rate of seven billion grams per year.
This chemical is still being produced as a feedstock for the manufacturing of other substances, they said.
Based on their calculations, the researchers believe if all banks were destroyed back in 2000, the measure would have saved the equivalent of 25 billion metric tonnes of carbon dioxide between 2000 and 2020, and there would be no CFC emissions lingering now from these banks.
In a second scenario, the researchers said, if the CFC banks are dismantled in 2020, it would help the ozone layer recover six years faster.
Nilima Marshall is the PA science reporter.