The ozone layer is recovering: What decades of cooperation can achieve

What has already been achieved

The positive news begins not with a forecast, but with a verifiable change: according to the Ozone Secretariat, around 99 per cent of controlled ozone-depleting substances have been phased out of production and use, measured by their ozone-depleting potential. These include chemicals previously used in refrigeration systems and foams, among other applications. The 2022 scientific assessment also describes evidence of recovery in the ozone layer. What matters here is the long-term trend, not the size of any single Antarctic ozone hole. For readers, this answers an obvious question: yes, reducing a human-made pressure can be reflected in the condition of a planetary protection system. However, there is a considerable time lag between the end of harmful emissions and full recovery.

Why recovery takes so long

Many ozone-depleting compounds remain in the atmosphere for a long time. Their effects therefore do not disappear when a fridge is replaced or production of a chemical ends. Provided that existing measures are maintained, the 2022 assessment expects a return to 1980 ozone levels outside the polar regions by around 2040. It gives a date of about 2045 for the Arctic and around 2066 for the Antarctic. These are model-based timescales, not guaranteed deadlines. Weather conditions and stratospheric dynamics have a considerable influence on annual measurements. A large ozone hole in a single year therefore does not automatically disprove long-term progress. Conversely, an unusually small hole would not, on its own, prove that all the problems had already been solved.

What makes this success transferable

The ozone layer limits the proportion of high-energy ultraviolet radiation that reaches the Earth's surface. Its recovery therefore matters to people, plants and ecosystems. Also noteworthy is the combination of research, technological change and ongoing monitoring: substances were identified, alternatives developed and changes observed over decades. This does not mean that every environmental crisis could be solved in the same way. The number of substances involved, economic structures and ecological relationships differ. But this case shows that jointly organised preventive action can deliver measurable results. The remaining task is to honour existing commitments, detect unexpected emissions and assess replacement substances carefully. Success here does not mean ending monitoring, but continuing it as an integral part of the solution.

Keep exploring

• One less pollutant in the tank: The worldwide end of leaded petrol for cars
• Humpback whales: a historic conservation success that needs a regional perspective
• More electric cars, less demand for oil: A measurable shift with limits