Gas harmful to ozone layer is declining sooner than expected, study finds

Hydrochlorofluorocarbons have started to decline after reaching a peak in 2021, according to work published Tuesday in the journal “Nature Climate Change”. That is, five years better than forecasts, thanks to the success of the Montreal Protocol.

International commitments to protect the ozone layer are bearing fruit as concentrations in the atmosphere of a family of harmful gases, hydrochlorofluorocarbons – HCFCs – have started to decline faster than expected, according to a study published Tuesday 11 June. “It’s a success and it makes us optimistic that climate and environmental treaties can work”welcomed Luke Western, of the University of Bristol, lead author of the study published in the journal Nature Climate Change.

The Montreal Protocol, signed in 1987, is an international commitment to gradually phase out ozone-depleting substances used in refrigeration, air conditioning, foam blowing and aerosols. This eliminated the production of chlorofluorocarbons, but hydrochlorofluorocarbons (HCFCs) were developed to replace them. These gases are present in air conditioners, refrigerators and even in the cooling system of cars. They are very effective in absorbing heat and producing cold, but they are harmful to the ozone which protects us from UV rays and powerful greenhouse gases.

Their production and use is still in the process of being eliminated. The international team publishing the study, however, demonstrated that the level of ozone-depleting chlorine from HCFCs has already reached its peak in 2021, five years earlier than expected. The researchers relied on measurements from a network of specialized measuring stations called AGAGE as well as data from the American meteorological agency NOAA.

“By implementing strict controls and promoting ozone-friendly alternatives, the protocol has succeeded in curbing emissions and levels of HCFCs in the atmosphere”welcomed Luke Western. “Without the Montreal Protocol, this success would not have been possible so it is a spectacular validation of multilateral commitments to combat the loss of the stratospheric ozone layer, with additional benefits in the fight against climate change. human origin”he judges.

The protection of the ozone layer is regularly cited by scientists as an example of successful collective action in favor of the environment. According to the latest four-year estimate from the United Nations Environment Program (UNEP), published in early 2023, the ozone layer should “reconstitute itself in the four decades to come”.