As the ozone layer recovers, it’s also intensifying global warming. Researchers predict that by 2050, ozone will rank just behind carbon dioxide as a driver of heating, offsetting many of the benefits from banning CFCs.
The planet is now expected to heat up more than scientists once predicted, and a major reason lies in the future behavior of ozone. This gas shields life on Earth from dangerous ultraviolet radiation, yet it also acts as a greenhouse gas by trapping heat in the atmosphere.
The ban on ozone-depleting chemicals such as CFCs has allowed the protective layer to steadily recover. But researchers warn that when this rebound is combined with rising levels of air pollution, ozone could drive 40% more warming than earlier estimates suggested.
Research led by the University of Reading shows that between 2015 and 2050, ozone will be responsible for an additional 0.27 watts per square meter (Wm⁻²) of trapped energy. This measurement refers to the amount of extra heat retained per square meter of the Earth’s surface. By mid-century, this would make ozone the second most important cause of warming, behind only carbon dioxide (1.75 W m⁻² of extra warming).
Professor Bill Collins, who led the study, explained: “Countries are doing the right thing by continuing to ban chemicals called CFCs and HCFCs that damage the ozone layer above Earth. However, while this helps repair the protective ozone layer, we have found that this recovery in ozone will warm the planet more than we originally thought.
“Air pollution from vehicles, factories, and power plants also creates ozone near the ground, causing health problems and warming the planet.”
The research, published on August 21 in Atmospheric Chemistry and Physics, used computer models to simulate how the atmosphere will change by the middle of the century. The models followed a scenario with low implementation of air pollution controls, but with CFCs and HCFCs being phased out as mandated by the Montreal Protocol (1987).
The findings show that stopping CFC and HCFC production – done mainly to protect the ozone layer – provides less climate benefit than previously calculated. CFCs and HCFCs are greenhouse gases that warm the planet. Countries banned them to save the ozone layer, expecting this would also help fight climate change. But as the ozone layer heals, it creates more warming that cancels out most of the climate benefits from removing CFCs and HCFCs.
Countries that reduce air pollution will limit some ozone formation near the ground. However, the ozone layer will continue repairing itself for decades regardless of air quality policies, creating unavoidable warming.
Protecting the ozone layer remains crucial for human health and preventing skin cancer. The ozone layer shields Earth from dangerous ultraviolet radiation that can harm people, animals and plants. However, the research suggests climate policies need updating to account for ozone’s larger warming effect.
