Ozone is best known as the invisible shield high in the atmosphere that protects us from the sun’s harmful ultraviolet rays.
But ozone is also a greenhouse gas, meaning it traps heat in the atmosphere and contributes to global warming.
A new study has found that this warming effect will be stronger than previously believed, raising concerns for the planet’s future.
The research, led by scientists at the University of Reading and published in Atmospheric Chemistry and Physics, suggests that by 2050, changes in ozone levels could warm the Earth about 40% more than earlier estimates.
Between 2015 and 2050, ozone is expected to trap an extra 0.27 watts of energy per square meter of the Earth’s surface.
While this may sound small, it makes ozone the second biggest contributor to global warming by mid-century—second only to carbon dioxide, which is projected to cause 1.75 watts per square meter of additional warming.
Professor Bill Collins, who led the study, explained that banning ozone-damaging chemicals such as CFCs and HCFCs has been a major environmental success story.
These chemicals, once used in refrigerators, air conditioners, and aerosols, were phased out worldwide under the 1987 Montreal Protocol after they were found to be destroying the ozone layer. “Countries are doing the right thing by continuing to ban these chemicals,” Collins said.
“But while this helps repair the ozone layer, our findings show that the recovery will also make the planet warmer than we originally thought.”
Ozone exists both high in the atmosphere, where it forms the protective layer, and near the ground, where it is created by air pollution from vehicles, factories, and power plants. At ground level, ozone is harmful to human health, causing breathing problems and aggravating lung conditions. It also adds to global warming.
The study used advanced computer models to simulate how the atmosphere might look by 2050. The models assumed that air pollution controls would remain weak in many regions, but that the world would continue to phase out ozone-destroying chemicals as agreed under the Montreal Protocol. The results revealed a mixed picture: while the decline of CFCs and HCFCs does reduce one type of warming, the recovery of the ozone layer itself creates extra warming that cancels out much of this benefit.
Even if some countries take stronger action on air pollution, the healing of the ozone layer will continue for decades regardless, meaning some of this warming effect is unavoidable.
Still, protecting the ozone layer remains vital. Without it, humans, animals, and plants would face dangerous levels of ultraviolet radiation, increasing the risk of skin cancer, eye damage, and harm to ecosystems. But the new findings suggest that climate policies must account for ozone’s larger role in warming the planet if we are to meet global climate targets.
In other words, while fixing the ozone hole has been a triumph for environmental policy, it has also brought an unexpected climate trade-off—one that scientists say we cannot afford to ignore.
