When science and politics come together: From depletion to recovery of the stratospheric ozone hole
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EDITORIAL
When science and politics come together: From depletion to recovery of the stratospheric ozone hole This article belongs to Ambio’s 50th Anniversary Collection. Theme: Ozone Layer Claudia Mohr
Published online: 21 November 2020
‘‘The world solved the ozone problem. It can solve climate change’’. Such was the headline of an opinion piece in The New York Times in 2019,1 when topics other than the COVID-19 pandemic still made headlines. It referred to the fact that the layer of ozone molecules present in the atmosphere was slowly recovering from destruction due to human activities. It was, however, also human action that had enabled the recovery of the ozone layer, and this sparked the outburst of optimism by The New York Times. Ambio had its role in this success story, as it was one of the journals where the scientific discoveries that laid the foundation for political action were discussed. Ozone (O3) is a natural constituent of the Earth’s atmosphere. It absorbs radiation in the ultraviolet (UV) and infrared (IR) ranges of the electromagnetic spectrum and plays therefore an important role in the regulation of the atmosphere’s radiation and temperature budget. High concentrations of ozone, the so-called ozone layer, are found in the stratosphere, at altitudes of 10 to 50 km in the atmosphere. The ozone layer shields humans, animals, and plants from biologically damaging UV radiation—without the absorptive properties of this molecule, life on Earth would not be possible. Ozone is formed from and reconverted to molecular oxygen via reactions that involve photodissociation. However, the levels of ozone found in the stratosphere can only be explained if additional loss mechanisms are taken into account. These are reaction cycles that involve catalysts such as hydrogen, hydroxyl, and halogen radicals such as bromine and chlorine, and nitrogen oxides (Crutzen 1974). This understanding was developed gradually in the second half of the last century. The work of chemists Paul Crutzen, Mario Molina, Sherwood Rowland, and colleagues in the 1970s led to the insight that the ozone layer in the stratosphere was being depleted and that the
substances responsible for the depletion were emitted by human activities: nitrogen oxides from the use of nitrates as fertilizers, and halogen radicals from chlorofluorocarbons (CFCs) and related compounds, used as propellant gas in aerosol spray cans, and refrigerants in refrigerators and airconditioners (Molina and Rowland 1974). Crutzen, Molina, and Rowland were awarded the Nobel Prize in Chemistry in 1995 for their work in atmospheric chemistry and specifically ozone formation and decomposition. Their work eventually led to one of the likely most successful agreements in the history of international environmental politics: The Montreal Protocol. Entered into force in 1989, this international treaty was designed to protect the ozone layer by phasing out the production of ozone-depleting substances, such as CFCs. Political pressure had grown after the detection of the ozone hole o
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