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.
Measuring Ozone’s Warming Impact
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.”
Simulating the Atmosphere’s Future
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.
Unavoidable Warming Ahead
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.
Reference: “Climate forcing due to future ozone changes: an intercomparison of metrics and methods” by William J. Collins, Fiona M. O’Connor, Rachael E. Byrom, Øivind Hodnebrog, Patrick Jöckel, Mariano Mertens, Gunnar Myhre, Matthias Nützel, Dirk Olivié, Ragnhild Bieltvedt Skeie, Laura Stecher, Larry W. Horowitz, Vaishali Naik, Gregory Faluvegi, Ulas Im, Lee T. Murray, Drew Shindell, Kostas Tsigaridis, Nathan Luke Abraham and James Keeble, 21 August 2025, Atmospheric Chemistry and Physics.
DOI: 10.5194/acp-25-9031-2025
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5 Comments
“The ban on ozone-depleting chemicals such as CFCs has allowed the protective layer to steadily recover.”
The Ozone Hole and the ‘depth’ of it are presented here: https://ozonewatch.gsfc.nasa.gov/
You tell me if it looks like there has been significant recovery. I think it is wishful thinking. To me, it appears that the last several years are much like it was in the 1990s.
Damned if you do, damned if you don’t. It has been said that if one is confronted with two plausible yet conflicting arguments, the best response is to reject them both.
I would suggest to examine the problem and see if there is a way to resolve the apparent conflict and accept both in an attempt for a win-win situation.
If that can’t be done, then one should avoid making any significant decisions or changes until more information is obtained to avoid the possibility of making the situation worse. If a situation is tolerable, and appears to be moving in a direction that is intolerable, then the last thing that one wants to do is accelerate it. That is, the wrong decision generally has more downside risk than doing nothing.
While it has been established that photo-catalytic destruction of ozone takes place in stratospheric ice clouds because of halogen gases absorbed onto the surface of the ice crystals, the so-called ‘Ozone Hole’ ALWAYS breaks down in the Spring when it warms and the circumpolar vortex breaks up, allowing the anomalously high concentrations of tropical ozone outside the vortex to move into the Antarctic region depleted of ozone. It is also observed that during some El Nino years, when it is warmer in Antarctica than La Nina or Neutral years, the ozone destruction is aborted and the ‘Hole’ is minimal. That is, temperature appears to be more important than the concentration of CFCs.
The decline in the size of the ‘Ozone Hole’ in the 1980s, concurrent with the international ban on CFCs, might be a spurious correlation that reflects a concern during the 1970s about entering another ice-age, which was followed by documented warming up until the present. If things don’t seem to make sense, always check one’s unstated, and usually unexamined, assumptions.
I grew up in the 70’s, and the ‘ice age’ argument gained traction because of the winters of ’77 and ’78. In ’77, my neck of the woods had a ten day period of negative double-digit high temps; on Jan.26 1978, I woke up to find there was eight feet of snow in our yard. And we haven’t had winters that bad since.
The sample size for climate changes needs to be much larger than we’re using now. We can detect trends, but that’s all.
It isn’t just sample size or length of time. Time-series can have periodic and aperiodic cycles, or random ‘runs’ like getting a dozen heads in a row while flipping a coin. Most people seem to be placing their bets on CO2, when the situation is more complex than a single determining variable.