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The substances destroying ozone

To understand the evolution of the ozone layer and check the effects of the Montreal Protocol, BIRA-IASB is also monitoring the stratospheric concentration of the main chlorinated and brominated species.


Chlorine gases

Remote sensing in the infrared range works particularly well in measuring the chlorine gases like

  • HCl,
  • ClONO2,
  • CFC’s
  • HCFC’s

This is why BIRA-IASB installed on the Ile de La Reunion, in the Indian Ocean, on the east of Madagascar, a Fourier transform spectrometer working in the solar infrared range. Since 2002, the data gathered by this spectrometer have been archived in the NDACC network data base.

The coordinated data analysis of this network shows:

  • a decline in chlorine gas sources whose production has been limited, or even totally stopped by the Montreal Protocol in 1987
  • a reduction of stratospheric HCl since 1996-1997

HCL measures


Brominated species

Measurements made by another spectrometer network, working this time in the ultraviolet spectral range and to which BIRA-IASB has been contributing since 1994, with an instrument installed in Norway, lead to the same conclusions for the brominated species.

These results, confirmed by data from the SCIAMACHY satellite orbiting Earth since 2002, univocally show the impact of the Montreal Protocol on the stratospheric concentration of the halogenated species destroying ozone. In this regard, they will be integrated into the next edition of the World Meteorological Organisation (WMO) report on the state of the ozone layer.



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