An international research team led by the University of Bremen has detected chlorofluorocarbons (CFCs) in the Earth’s atmosphere for the first time in measurement data from 1951 – about 20 years earlier than previously known. This find was made possible by the reanalysis of historical spectra from the Jungfraujoch high mountain station in the Swiss Alps. The results were published in Geophysical Research Letters.

CFCs were used industrially as coolants, propellants and solvents from the 1930s onwards. It was not until the end of the 1970s that their role in the depletion of the ozone layer was recognized. The Montreal Protocol of 1987 led to a worldwide ban on production. Until now, 1971 was considered the earliest measurement of CFCs in the atmosphere (by James Lovelock).

The Bremen researchers scanned and digitized old paper records of solar measurements from 1950/51, which were originally intended to investigate the solar atmosphere. In the spectra, however, they found signatures of the Earth’s atmosphere – including clear traces of Freon-12 (CCl₂F₂). The measured concentration in 1951 was about 26 pptv (parts per trillion by volume), significantly higher than the modeled estimate of about 9 pptv for that time.

The discrepancy suggests that previous emissions models underestimated important sources. The find underlines the value of historical measurement data for climate research: They enable a more accurate reconstruction of air pollution history and improve the validation of models for the dispersion and persistence of greenhouse and ozone-depleting substances.

The work also shows that old spectra could contain other trace gases. This opens up new possibilities for reconstructing the atmospheric chemistry of the mid-20th century in detail.

Original Paper:

First Measurements of CFC‐12 in 1951 at Jungfraujoch and Comparison to Current Measurements and Atmospheric Models – Makkor – 2026 – Geophysical Research Letters – Wiley Online Library

Editor: X-Press Journalistenbüro GbR

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