Timeline of the Ozone Layer
The discovery, measurement and protection of stratospheric ozone, from identifying ozone in 1840 to the Antarctic ozone hole, international chemical controls and evidence of recovery through 2023.
- Category
- Natural Sciences
- Events
- 20 events 1840–2023
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- by gpt-6-astra
1840: Schönbein identifies and names ozone
Christian Friedrich Schönbein recognized a distinctive gas produced during electrical experiments and named it ozone. Identifying the substance preceded understanding its role high in the atmosphere, where it absorbs ultraviolet radiation.
Wikipedia1913: Fabry and Buisson identify the ozone layer
Charles Fabry and Henri Buisson used ultraviolet measurements to establish the presence of atmospheric ozone responsible for strong absorption of solar radiation. Their work helped locate an atmospheric shield whose importance could not be inferred from ozone near the ground.
Wikipedia1924: Dobson develops an instrument for ozone monitoring
Gordon Dobson developed a spectrophotometer that estimated atmospheric ozone from differences in ultraviolet absorption. Standardized instruments later supported long-running measurements across an international network, making changes detectable against a historical baseline.
Wikipedia1930: Chapman explains ozone's photochemical cycle
Sydney Chapman described how sunlight could create and destroy stratospheric ozone through reactions involving oxygen molecules and atoms. The model supplied a starting point for atmospheric chemistry, although additional reactions were needed to explain measured ozone amounts.
Wikipedia1930: Midgley demonstrates a chlorofluorocarbon refrigerant
Thomas Midgley Jr. publicly demonstrated a chlorofluorocarbon developed with Albert Henne and Robert McNary as an alternative to toxic or flammable refrigerants. Its low reactivity later proved important because it allowed the gas to persist and reach the stratosphere.
Wikipedia1956: Halley begins a long Antarctic ozone record
Ozone observations began at the newly established Halley station in preparation for the International Geophysical Year. The sustained record later allowed British Antarctic Survey scientists to distinguish an emerging springtime decline from ordinary short-term fluctuations.
Wikipedia1970: Crutzen identifies nitrogen oxides as ozone catalysts
Paul Crutzen showed how nitrogen oxides could catalytically destroy stratospheric ozone. His work demonstrated that small quantities of reactive chemicals could strongly affect ozone abundance and broadened concern about human influences on atmospheric chemistry.
Wikipedia1974: Molina and Rowland warn about chlorofluorocarbons
Mario Molina and Frank Sherwood Rowland proposed that chlorofluorocarbons could reach the stratosphere, where ultraviolet light would release chlorine that destroyed ozone catalytically. Their paper connected widely used industrial chemicals to a global atmospheric risk.
Wikipedia1978: The United States restricts aerosol propellants
The United States banned most nonessential uses of chlorofluorocarbons as aerosol propellants. Refrigeration and other applications continued, so the measure addressed only part of the emissions later covered by international agreements.
Wikipedia1985: Governments adopt the Vienna Convention
The Vienna Convention for the Protection of the Ozone Layer established a framework for research, monitoring and international cooperation. Adopted in March, before publication of the Antarctic ozone-hole paper, it did not itself set binding chemical phaseout schedules.
Wikipedia1985: Antarctic measurements reveal severe springtime ozone loss
Joe Farman, Brian Gardiner and Jonathan Shanklin reported unexpectedly large springtime ozone losses above Antarctica. The ozone hole described severe seasonal depletion, not an empty opening in the atmosphere, and prompted intensive investigation of polar chemistry.
Wikipedia1986: Solomon and colleagues explain polar cloud chemistry
Susan Solomon and colleagues proposed that reactions on polar stratospheric clouds activated chlorine compounds that rapidly destroyed ozone when sunlight returned. Antarctic measurements helped test the chemical explanation for the unusually severe seasonal losses.
Wikipedia1987: The Montreal Protocol sets chemical controls
Governments agreed to control production and consumption of major ozone-depleting substances under the Montreal Protocol. The treaty entered into force in 1989, and later revisions strengthened its schedules and expanded the chemicals covered.
Wikipedia1990: The London Amendment strengthens the phaseout
Parties to the Montreal Protocol agreed to phase out additional ozone-depleting substances and created a funding mechanism to help developing countries comply. The agreement linked tighter controls with technical and financial assistance.
Wikipedia1992: The Copenhagen Amendment accelerates controls
Parties tightened phaseout schedules and added controls for further ozone-depleting substances, including hydrochlorofluorocarbons and methyl bromide. Successive revisions allowed the treaty to respond to scientific findings and the availability of substitutes.
Wikipedia1995: Ozone chemistry earns the Nobel Prize
The Nobel Prize in Chemistry went to Paul Crutzen, Mario Molina and Frank Sherwood Rowland for research on atmospheric chemistry, particularly ozone formation and decomposition. The award recognized the scientific work underlying concern about ozone-depleting emissions.
Wikipedia2016: Researchers detect Antarctic ozone-hole healing
Susan Solomon and colleagues reported evidence of improvement in Antarctic September ozone since 2000. They separated the influence of declining ozone-depleting chemicals from meteorological variability and volcanic effects; recovery did not mean that the seasonal hole had disappeared.
Wikipedia2016: The Kigali Amendment addresses warming refrigerants
Parties agreed in Kigali to phase down hydrofluorocarbons, refrigerants that had replaced some ozone-depleting substances. These gases did not directly deplete ozone but were potent greenhouse gases, extending the treaty system's role in climate protection.
Wikipedia2018: Unexpected emissions reveal a setback in controls
Atmospheric measurements revealed an unexpected rise in emissions of trichlorofluoromethane, also called CFC-11, despite its scheduled phaseout. The finding demonstrated why long-term monitoring remained necessary even after international controls had been adopted.
Wikipedia2023: An international assessment confirms signs of recovery
The United Nations' ozone assessment reported continuing recovery in the upper stratosphere and declining concentrations of controlled ozone-depleting substances. Large year-to-year changes in the Antarctic ozone hole persisted, so a single season did not establish the long-term trend.
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