To mark the International Day for the Preservation of the Ozone Layer on 16 September, GeoSphere Austria highlights the importance of global cooperation. International cooperation brought an end to the use of ozone-depleting chlorofluorocarbons (CFCs). CFCs have largely disappeared from everyday life; the ozone layer is regenerating and is expected to have largely recovered by 2040.
1985 was a pivotal year for the Earth’s ozone layer. That year, three researchers from the British Antarctic Survey published their alarming findings: the ozone layer over Antarctica had thinned dramatically over the course of around 20 years. So much so that the term ‘ozone hole’ was soon coined. In the very same year, 28 countries adopted a convention in Vienna to protect the ozone layer. And just two years later, in 1987, concrete measures were agreed under the Montreal Protocol.
A view of the Earth’s atmosphere with the ozone layer, which absorbs a large proportion of UV radiation. © iStock/studio023.
‘The international community reacted swiftly in the 1980s. CFCs have largely disappeared from our everyday lives, and the ozone layer is beginning to recover – slowly but surely,’ confirms Andreas Schaffhauser, Scientific Director-General of GeoSphere Austria. According to current forecasts, it is expected to have largely recovered by 2040, returning to 1980 levels. It will take considerably longer in Antarctica, where the ‘ozone hole’ is not likely to be closed until 2066.
In a three-part podcast, GeoSphere Austria meteorologists Liliane Hofer and Christian Resch recount the history of the ozone layer and also explore whether the measures taken back then to save it could serve as a model for current climate policy.
‘Unfortunately, only to a limited extent,’ Hofer and Resch point out. ‘Because the ozone problem involved a manageable number of substances that could be replaced by other technologies.’ Furthermore, poorer countries received financial support during the transition. ‘With climate change, the problem is significantly greater. Carbon dioxide is produced practically wherever we burn coal, oil and gas.’ A fundamental overhaul of our energy and economic systems is therefore necessary. The aim must be to bring CO₂ emissions down to net zero as quickly as possible.
As early as 1970, the Dutch atmospheric chemist Paul Crutzen had discovered that nitrogen oxides break down large quantities of ozone in the stratosphere. Four years later, Mario Molina and Sherwood Rowland discovered substances that posed an even greater threat to the ozone layer: these were chlorofluorocarbons – better known by the abbreviation CFCs. These CFCs had been invented as early as the 1920s and originally served a perfectly good purpose: ‘They replaced more dangerous substances such as propane, sulphur dioxide and ammonia in fridges. CFCs themselves, however, were neither toxic nor flammable and appeared to be chemically extremely stable,’ explain Liliane Hofer and Christian Resch in the final part of their three-part podcast series ‘The Ozone Trilogy’. CFCs were also used worldwide as propellants in aerosol cans.
The extremely stable and long-lived CFC molecules are distributed across the entire planet. In the tropics, air rises into higher layers – carrying the CFCs with it to altitudes of 15 to 35 kilometres. Once there, they are broken down by high-energy UV radiation. “Chlorine radicals are released, which in turn destroy ozone molecules. This produces oxygen, but this offers us hardly any protection against UV radiation. That is precisely why ozone in the stratosphere is so important,” emphasise Hofer and Resch. What’s more, even a relatively small amount of chlorine radicals is enough to deplete a great deal of ozone. Under the right conditions, a single chlorine atom can destroy up to around 100,000 ozone molecules.
Translated with DeepL.com (free version)
