First Measurements of CFC-12 in 1951 at Jungfraujoch and Comparison to Current Measurements and Atmospheric Models

Chlorofluorocarbons (CFCs) have played a major role in the depletion of stratospheric ozone. Understanding historical trends in emissions and atmospheric concentrations is crucial for quantifying their impact. The first measurements of atmospheric CFCs were performed in-situ by Lovelock in 1970. We have analyzed historical 1951 solar absorption infrared spectra, recorded at Jungfraujoch, to retrieve the CFC-12 surface mole fraction. We compare to routine solar absorption measurements starting at Jungfraujoch in 1986 and emission-based forward models. The surface mole fraction derived from the historical spectra is (26.1 ± 18.5) pptv compared to (9.2 ± 0.2) pptv from a reconstructed history model, and (7.00 ± 0.28) pptv from the Advanced Global Atmospheric Gases Experiment 12-Box model. The 1951 measurement and model values agree within error bars although the models may be biased low due to unreported emissions. Our result represents the earliest atmospheric CFC measurement, predating Lovelock's detection by over two decades.