Restoring it is key for human health, food security and the planet. UV-B radiation causes cancer and eye damage in humans. It also damages plants, inhibiting their growth and curbing their ability to store planet-warming carbon dioxide.
“Ozone action sets a precedent for climate action,” World Meteorological Organization Secretary General Petteri Taalas said in a statement. “Our success in phasing out ozone-eating chemicals shows us what can and must be done — as a matter of urgency — to transition away from fossil fuels, reduce greenhouse gases and so limit temperature increase.”
Those improvements will not be steady, scientists stressed, given natural fluctuations in ozone levels and the ozone-inhibiting influence of volcanic eruptions like the massive one from underwater Pacific Ocean volcano Hunga Tonga a year ago.
A recent decline in observed levels of the chemical known as CFC-11, in particular — which as recently as 2018 had been observed at higher-than-expected levels and traced to China — is proof that societies can collaborate to address a confounding environmental problem, said Martyn Chipperfield, a professor at the University of Leeds who serves on the scientific panel.
Ozone is a molecule made of three oxygen atoms, and it proliferates in a layer of the stratosphere about nine to 18 miles above the ground. It can exist at ground level, too, where it is a product of air pollution on hot summer days and considered a health hazard. But in the atmosphere, it serves as an essential shield protecting Earth’s life from harmful ultraviolet radiation.
In the same way that UV lights eradicate pathogens like the virus responsible for covid-19, the sun’s radiation would make it impossible for life to thrive on Earth if not for the ozone layer’s protection. UV-B, a high-energy form of solar radiation, damages DNA in plants and animals, disrupting a variety of biological processes and reducing the efficiency of photosynthesis.
The Montreal Protocol, which has been approved by every country in the world, protects the ozone by outlawing the manufacturing and use of substances that destroy it when they come in contact with it in the atmosphere. That largely includes a class known as chlorofluorocarbons or CFCs, which contain ozone-depleting chlorine and were used in refrigerators, air conditioners and aerosol cans.
“We can already see HFCs are not increasing as fast as we thought they would because countries are starting to implement their own controls,” said Paul Newman, one of four co-chairs of the Scientific Assessment Panel of the Montreal Protocol.
Progress would likely also be slowed if humans pursue geoengineering to reverse global warming by injecting sunlight-reflecting particles into the upper atmosphere, Newman said. The panel, which considered the potential impact of that practice for the first time for Monday’s report, found that, depending on the timing, frequency and amount of such injections, the particles could alter aspects of atmospheric chemistry that are important in ozone development.
