The ozone layer is on track to fully recover from its depletion within the next four decades, a panel of scientists gathered by the United Nations said on Monday.
In an assessment conducted every four years on the progress of the Montreal Protocol, the 1987 agreement between over 180 countries to phase out the chemicals causing ozone depletion, the group confirmed an almost 99% reduction in emissions of ozone-damaging substances banned by the agreement. That is allowing the ozone layer — a section of the stratosphere that contains high concentrations of ozone, or trioxygen (O3), which absorbs ultraviolet (UV) rays — to gradually recover. The phenomenon of ozone depletion was first discovered in the 1970s and the United States banned “nonessential” CFC use in aerosol spray cans in 1978, but the 1984 discovery of a hole in the ozone layer over Antarctica spurred the international community to act.
“In the upper stratosphere and in the ozone hole we see things getting better,” Paul Newman, co-chair of the scientific report, told the Associated Press.
If present trends continue, the assessment projects that the ozone layer’s average thickness will be returned to 1980 levels by 2040. Since the ozone layer has thinned the most at the poles, it is expected to take until 2045 to return to pre-depletion levels over the Arctic and around 2066 in the Antarctic. There is currently a 8.91-million-square-mile hole in the ozone layer over Antarctica, according to the National Oceanic and Atmospheric Administration, but that hole has been gradually shrinking since 2000.
The thinning of the ozone layer allows UV rays to reach the Earth, increasing the prevalence of conditions including cataracts and skin cancer, and causing damage to crops such as soybeans.
The Montreal Protocol required the phase-out of chlorofluorocarbons, also known as CFCs, chemicals used in refrigerants and aerosols that cause ozone depletion. CFCs are also greenhouse gases that cause global warming. The U.N. report estimates that by ending the use of CFCs, the world has prevented 0.5 degrees Celsius (0.9 Fahrenheit) of warming.
“The impact the Montreal Protocol has had on climate change mitigation cannot be overstressed,” Meg Seki, executive secretary of the U.N. Environment Programme’s Ozone Secretariat, said in a statement. “Over the last 35 years, the Protocol has become a true champion for the environment.”
An addition to the Montreal Protocol, known as the Kigali Amendment, which requires member nations to phase down the use of some hydrofluorocarbons, or HFCs, which do not cause ozone layer depletion and have replaced CFCs in many products, was negotiated in 2016. HFCs have also turned out to be greenhouse gases. The Kigali Amendment, which was ratified by the Senate last year, will prevent another 0.3° to 0.5°C of global temperature rise by the end of this century, according to the new assessment.
Experts say that the Montreal Protocol’s structure and its success have provided the template that action to prevent catastrophic climate change could follow.
“Ozone action sets a precedent for climate action,” said World Meteorological Organization Secretary-General Petteri Taalas, in response to the new report. “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.”