Researchers modelling the impact of increases in certain types of chemicals have shown that progress made to close the hole in the ozone layer above the Antarctic may slow if emissions continue.

Publishing in the journal Nature Communications their modelling study shows the recently discovered increase in emissions of trichlorofluoromethane (CFC-11) may delay the recovery of the Antarctic ozone hole by over a decade if it continues.

Although uncertainties exist regarding the levels of CFC-11 emissions and how they may vary, a rapid halt to their occurrence may limit the delay to only a few years.

CFC-11 contributes about one quarter of the anthropogenic chlorine transported into the stratosphere and its production is controlled by the 1987 Montreal Protocol – a global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS).

Following the implementation of the protocol, return of the Antarctic ozone hole to pre-depletion 1980 levels is expected to occur early in the second half of the 21st century.

However, in 2018 it was reported that CFC-11 emissions had not been declining as expected since the mid-2000s. This is likely to be related to emissions from unreported production for insulation foam use in China.

Martyn Chipperfield from the University of Leeds and colleagues including Lancaster University’s Dr Ryan Hossaini used a detailed atmospheric chemical transport model to investigate the impact of these additional emissions on polar ozone recovery.

The authors studied three possible CFC-11 emissions pathways: emissions stopping immediately, emissions continuing at a constant level, or emissions being phased out over the next 10 years. The simulations suggest that the impact on the ozone hole has been limited so far. However, if emissions continue at a constant level, this could delay the ozone returning to 1980 values by around 18 years. If the emissions were phased out over the next decade, the delay will likely be no more than two years.

Dr Hossaini said: “The Montreal Protocol has been a phenomenal success and in consequence the Antarctic Ozone Hole that forms each spring should cease to exist in the latter half of this century. However, the timetable for ozone layer recovery should not be taken for granted. These results show that uncertainty on that timetable has now increased due to the unexpected CFC-11 emissions. It is paramount that we remain vigilant to this and any other emerging factors that could slow progress.”

The DOI number for this paper is 10.1038/s41467-019-13717-x.

It is available at the following URL: https://www.nature.com/articles/s41467-019-13717-x.