Spectrometric monitoring of atmospheric carbon tetrafluoride (CF₄) above the Jungfraujoch station since 1989: evidence of continued increase but at a slowing rate

Abstract. The long-term evolution of the vertical column abundance of carbon tetrafluoride (CF₄) above the high-altitude Jungfraujoch station (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.) has been derived from the spectrometric analysis of Fourier transform infrared solar spectra recorded at that site between 1989 and 2012. The investigation is based on a multi-microwindow approach, two encompassing pairs of absorption lines belonging to the R-branch of the strong ν₃ band of CF₄ centered at 1283 cm⁻¹, and two additional ones to optimally account for weak but overlapping HNO₃ interferences. The analysis reveals a steady accumulation of the very long-lived CF₄ above the Jungfraujoch at mean rates of (1.38 ± 0.11) × 10¹³ molec cm⁻² yr⁻¹ from 1989 to 1997, and (0.98 ± 0.02) × 10¹³ molec cm⁻² yr⁻¹ from 1998 to 2012, which correspond to linear growth rates of 1.71 ± 0.14 and 1.04 ± 0.02% yr⁻¹ respectively referenced to 1989 and 1998. Related global CF₄ anthropogenic emissions required to sustain these mean increases correspond to 15.8 ± 1.3 and 11.1 ± 0.2 Gg yr⁻¹ over the above specified time intervals. Findings reported here are compared and discussed with respect to relevant northern mid-latitude results obtained remotely from space and balloons as well as in situ at the ground, including new gas chromatography mass spectrometry measurements performed at the Jungfraujoch since 2010.