Notable decline seen in ozone depleting gases

For the first time, a study led by the University of Bristol shows a ‘notable decline’ in the levels of  hydrochlorofluorocarbons (HCFCs), which deplete the ozone layer and are also harmful greenhouse gases.

While in themselves environmentally unsatisfactory, HCFCs were introduced to replace chlorofluorocarbons (CFCs), which are considerably worse and the production of which was banned in 2010. HCFCs themselves are currently being phased out.

The high-altitude Integrated Carbon Observation System in Switzerland, which was used to make measurements in the research.

The US National Oceanic and Atmospheric Administration’s (NOAA) Global Monitoring Laboratory explain the difference between the two thus:

‘HCFCs are compounds containing carbon, hydrogen, chlorine and fluorine. Industry and the scientific community view certain chemicals within this class of compounds as acceptable temporary alternatives to chlorofluorocarbons. The HCFCs have shorter atmospheric lifetimes than CFCs and deliver less reactive chlorine to the stratosphere where the ‘ozone layer’ is found.

‘Consequently, it is expected that these chemicals will contribute much less to stratospheric ozone depletion than CFCs. Because they still contain chlorine and have the potential to destroy stratospheric ozone, they are viewed only as temporary replacements for the CFCs. Current international legislation has mandated production caps for HCFCs; production is prohibited after 2020 in developed countries and 2030 in developing countries.’

The results of the new research are based on high-precision measurements at globally distributed atmospheric observatories, using data from the Advanced Global Atmospheric Gases Experiment (AGAGE) and the NOAA.

The results show the total amount of ozone depleting chlorine contained in all HCFCs peaked in 2021, meaning that their contribution to climate change also peaked then, five years earlier than predicted.

Lead author Dr Luke Western, Marie Curie Research Fellow at the University’s School of Chemistry, said: ‘The results are very encouraging. They underscore the great importance of establishing and sticking to international protocols.

‘Without the Montreal Protocol [1987’s global agreement to phase out ozone-depleting substances], this success would not have been possible, so it’s a resounding endorsement of multilateral commitments to combat stratospheric ozone depletion, with additional benefits in tackling human-induced climate change.

‘Their production is currently being phased out globally, with a completion date slated for 2040. In turn these HCFCs are being replaced by non-ozone depleting hydrofluorocarbons (HFCs) and other compounds. By enforcing strict controls and promoting the adoption of ozone-friendly alternatives, the protocol has successfully curbed the release and levels of HCFCs into the atmosphere.’

‘We use highly sensitive measurement techniques and thorough protocols to ensure the reliability of these observations,’ said co-author Dr Martin Vollmer, an atmospheric scientist at the Swiss Federal Laboratories for Materials Science and Technology (EMPA).

Co-author Dr Isaac Vimont, a research scientist at the NOAA in the United States, added: ‘This study highlights the critical need to be vigilant and proactive in our environmental monitoring, ensuring other controlled ozone depleting and greenhouse gases follow a similar trend which will help to protect the planet for future generations.’