by For the first time, researchers have observed a significant reduction in atmospheric levels of hydrochlorofluorocarbons – harmful gases that deplete the ozone layer and warm the planet.
Almost 30 years after nations agreed to phase out these chemicals, which were widely used for air conditioning and refrigeration, scientists say that a global peak has occurred in 2021. Since then, the ozone-depleting potential of HCFCs in the atmosphere. a quarter of a percentage point, according to findings published Tuesday in the journal Nature Climate Change.
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Although small, that decline comes earlier than expected, scientists say – and is a significant milestone in the international effort to preserve the layer of Earth’s stratosphere that blocks dangerous ultraviolet light.
As humanity struggles to control greenhouse gas pollution that has pushed global temperatures to unprecedented highs, scientists said the breakthrough on HCFCs is a hopeful sign.
“This is a great success story that shows how global policies are protecting the planet,” it said Veerabhadran Ramanathanclimate scientist at the University of California at San Diego and Cornell University who were not involved in the new study.
Just over 50 years ago, researchers realized that a hole was forming in the ozone layer over Antarctica, allowing cancer-causing radiation to reach the Earth’s surface. The main culprits were chlorofluorocarbons (CFCs), which can destroy thousands of ozone molecules with a single chlorine atom and remain in the atmosphere for centuries.
The discovery prompted countries to sign the 1987 Montreal Protocol, agreeing to phase out the production of CFCs. Under the terms of the agreement, rich countries would stop production first and provide financial and technical assistance to low-income nations while also moving away from the polluting chemicals. The production of CFCs has been banned worldwide since 2010.
But the most common replacements were HCFCs – compounds that have about one-tenth the ozone-depleting potential of CFCs, but can still cause significant damage. The most commonly used HCFC has approximately 2,000 times the heat-trapping potential of carbon dioxide over a 100-year period. Therefore, in 1992 nations agreed that they would abandon the chemicals as well.
“The transition went well,” said University of Bristol researcher Luke Western, lead author of the Nature Climate Change study.
The United Nations estimates that the world has banned 98 percent of ozone-depleting substances being produced in 1990. These manufacturing bans take decades to produce fewer products sold and fewer HCFCs. transfer in the atmosphere. But the Western research, which drew on data from two global air monitoring programs, shows that a turning point has finally come.
The contribution of HCFCs to climate change peaked at about 0.05 degrees Celsius (almost a tenth of a degree Fahrenheit), West said, and their abundance in the atmosphere is expected to return to 1980 levels by 2080.
“This milestone is a testament to the power of international cooperation,” said Avipsa Mahapatra, director of the Environmental Investigation Agency’s climate campaign. “To me, that’s a sign that there’s the potential to do a lot more, and it gives me climactic hope.”
Mahapatra said the success of the Montreal Protocol could spur efforts to curb planet-warming pollution – something that was very successful last year. By setting out clear, enforceable goals that were informed by each nation’s needs, she said, the accord encouraged people to take action while remaining the only treaty signed by every country in the world. He is credited with helping the world avoid millions of cases of skin cancer and as much as a full degree Celsius (1.8 degrees Fahrenheit) of warming.
But the work is not done, said Mahapatra. While HCFCs were a flawed substitute for CFCs, they have now been replaced by a new class of refrigerants – hydrofluorocarbons (HFCs) – which are considered “super pollutants” for the climate. Although the Montreal Protocol was amended in 2016 to demand a reduction in the use of HFCs, they are often used in air conditioners, refrigerators and insulation.
Ultimately, transitioning away from fossil fuels will be much more complicated than curbing the production of ozone-depleting substances, Western said. The Montreal Protocol affected relatively little industry, and only required companies to change their products – not their entire businesses.
With climate change, “You’re up against a bigger beast in some ways,” Western said.
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