For the first time, researchers have detected a significant drop in atmospheric levels of hydrochlorofluorocarbons, harmful gases that deplete the ozone layer and warm the planet.
Almost 30 years after nations first decided to phase out these chemicals, which are widely used in air conditioning and refrigeration, scientists say global concentrations have peaked in 2021. Since then, the potential for HCFCs to deplete the atmospheric ozone layer has decreased by approximately threefold. There was a quarter-point increase, according to findings published Tuesday in the journal Nature Climate Change.
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Scientists say the decline, although small, occurred earlier than expected and represents a significant milestone in international efforts to protect Earth’s stratosphere, which blocks dangerous ultraviolet sunlight.
As humanity struggles to control greenhouse gas pollution that has driven global temperatures to unprecedented levels, scientists said the progress on HCFCs was a hopeful sign.
“This is a remarkable success story that shows how global policies protect the planet,” he said Veerabhadran Ramanathana climate scientist at the University of California at San Diego and Cornell University who was not involved in the new study.
A little more than 50 years ago, researchers noticed that a hole had formed 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 hundreds of years.
The discovery led countries to sign the 1987 Montreal Protocol, agreeing to phase out CFC production. Under the terms of the agreement, rich countries will first halt production and provide financial and technical assistance to low-income countries as they transition away from polluting chemicals. The production of CFCs has been banned worldwide since 2010.
But the most common substitutes 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 also has approximately 2,000 times the heat retention potential of carbon dioxide over a 100-year period. Thus, in 1992, countries agreed to abandon these chemicals as well.
“The transition has been hugely successful,” said University of Bristol researcher Luke Western, lead author of the Nature Climate Change study.
The United Nations estimates that 98 percent of ozone-depleting substances produced in the world in 1990 had been stopped. It takes decades for these production bans to translate into fewer product sales and fewer HCFCs in the atmosphere. But Western’s research, based on data from two global weather monitoring programs, suggests the turning point has finally arrived.
HCFCs’ contribution to climate change peaks at about 0.05 degrees Celsius (almost one-tenth of a degree Fahrenheit), and their abundance in the atmosphere is expected to return to 1980 levels by 2080, Western said.
“This milestone is a testament to the power of international cooperation,” said Avipsa Mahapatra, climate campaign director at the Environmental Investigation Agency. “To me, this points to the potential to do so much more and gives me hope for climate.”
Mahapatra said the success of the Montreal Protocol could inspire efforts to curb planetary warming, which hit a record high last year. The agreement, which sets clear and actionable targets that recognize the needs of each nation, encourages people to take action while remaining the only agreement signed by every country in the world, she said. It is credited with helping the world avoid millions of cases of skin cancer and a full degree Celsius (1.8 degrees Fahrenheit) of warming.
But the work is not yet done, Mahapatra said. Although HCFCs were an imperfect substitute for CFCs, they have now been superseded by hydrofluorocarbons (HFCs), a new class of refrigerants that are considered climate “super pollutants.” Although the Montreal Protocol was amended in 2016 to call for reducing the use of HFCs, HFCs are frequently used in air conditioners, refrigerators and insulation.
Ultimately, moving away from fossil fuels will be much more complex than simply blocking the production of ozone-depleting substances, Western said. The Montreal Protocol affected a relatively small industry and required companies to change only their products, not their entire business.
With climate change, “In some ways you’re dealing with a bigger beast,” Western said.
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