As much of the world’s nations struggle to make sufficient progress on reducing carbon emissions, new research has emerged showing that global collaboration can in fact reverse some of the harmful effects of human activity. A study published in the journal Nature Climate Change documented the first significant drop in atmospheric levels of hydrochlorofluorocarbons (HCFCs), harmful gases known to deplete the planet’s ozone layer.

The study from researchers at the University of Bristol found a 1% drop in HCFC emissions between 2021 and 2023. While the drop-off might seem small, it marks the first time ever a decline in the compound’s presence has been detected. Even better, the findings suggest that HCFC usage peaked in 2021, nearly five years ahead of schedule.

A brief history on HCFCs

HCFCs are human-made compounds containing hydrogen, chlorine, fluorine and carbon, and are commonly used in refrigerants, aerosol sprays, and packaging foam. They were used as a replacement for chlorofluorocarbons (CFCs), more commonly known as Freon.

CFCs were widely believed to be harmless—they are nontoxic, nonflammable and don’t have any unstable reactions with other common chemicals. But, in the 1970s, scientists Mario Molina and F. Sherwood Rowland managed to link the depletion of the ozone layer to the use of these chemical compounds.

That discovery was foundational to the Montreal Protocol, an international treaty signed by 198 countries seeking to phase out the use of substances that harm the ozone layer, the planet’s shield against ultraviolet radiation from the Sun. The agreement set forth a number of goals that would lead to the reduction and eventual elimination of ozone-depleting substances.

The first stage of the Montreal Protocol was the elimination of CFCs, and proved to be wildly successful. A 2022 report from the United Nations found that nearly 99% of all CFCs had been phased out. The report estimates that ditching CFCs, which are also greenhouse gases that trap heat in the Earth’s atmosphere, managed to avoid an increase of 0.5 to 1 degrees Fahrenheit to the planet’s temperature by 2100.

Promising results in the fight against ozone depletion

The success of the treaty now appears to be extending to HCFCs. The Freon replacement took off as a sort of harm-reduction strategy because it provided similar functionality as CFCs while doing less damage to the ozone. But, like CFCs before them, HCFCs are a greenhouse gas and contribute to planetary warming. The Montreal Treaty mandated a ban on this compound by 2020 for developed nations, and the latest study suggests the restrictions are working.

“The results are very encouraging. They underscore the great importance of establishing and sticking to international protocols,”  Dr. Luke Western, Marie Curie Research Fellow at the University of Bristol School of Chemistry and lead author on the paper, said in a statement. “Without the Montreal Protocol, this success would not have been possible, so it’s a resounding endorsement of multilateral commitments to combat stratospheric ozone depletion, with additional benefits in tackling human-induced climate change.”

The success of the Montreal Protocol isn’t just seen in the dwindling levels of harmful chemicals in the atmosphere, but can also be seen in the slow but steady decrease in the hole in the ozone layer. According to the UN, the ozone layer is expected to recover to 1980 levels by 2040 for most of the world. That would mark a return to health for the protective part of the stratosphere that would match levels before holes in the shield were first discovered.

As nations continue debating the best way to reduce carbon emissions and combat climate change, the Montreal Protocol offers a proof of concept for global cooperation. A concerted effort toward a common goal can make a difference.