For the first time, researchers have detected a significant dip in atmospheric levels of hydrochlorofluorocarbons — harmful gases that deplete the ozone layer and warm the planet.
Almost 30 years after nations first agreed to phase out these chemicals, which were widely used for air conditioning and refrigeration, scientists say global concentrations peaked in 2021. Since then, the ozone-depleting potential of HCFCs in the atmosphere has fallen by about three-quarters of a percentage point, according to findings published Tuesday in the journal Nature Climate Change.
Though small, that decline comes sooner than expected, scientists say — and it represents a significant milestone for the international effort to preserve the layer of Earth’s stratosphere that blocks dangerous ultraviolet sunlight.
Just over 50 years ago, researchers realized that a hole was forming in the ozone layer over Antarctica, allowing cancer-causing radiation to reach Earth’s surface. The main culprits were chlorofluorocarbons (CFCs), which could destroy thousands of ozone molecules with a single chlorine atom and linger in the atmosphere for hundreds of years.
The discovery prompted countries to sign the 1987 Montreal Protocol, agreeing to phase out production of CFCs. Under the terms of the agreement, rich countries would halt production first and provide financial and technical assistance to low-income nations as they also moved away from the polluting chemicals. Production of CFCs has been banned globally since 2010.
But the most common replacements were HCFCs — compounds that have about one-tenth of the ozone-depleting potential of CFCs, but could still cause significant damage. The most commonly used HCFC also has roughly 2,000 times the heat-trapping potential of carbon dioxide over a 100-year period. So in 1992 nations agreed they would abandon these chemicals as well.
“The transition has been pretty successful,” said University of Bristol researcher Luke Western, the lead author of the Nature Climate Change study.
The United Nations estimates that the world has curbed 98 percent of the ozone-depleting substances being produced in 1990. It takes decades for those manufacturing bans to translate into fewer products sold and fewer HCFCs in the atmosphere. But Western’s research, which drew on data from two global air monitoring programs, shows that turning point has finally arrived.
https://wapo.st/4bUznW6
What's interesting is that the President who decided to undertake the negotiations that led to this outcome was a conservative Republican. Ronald Reagan.
George H.W. Bush, as president, negotiated a treaty with Canada that has been very successful in curbing acid rain.