Ozone-depleting chemicals are again on the rise. Here’s why

Despite a global ban in place since 2010, atmospheric concentrations of five ozone-depleting chemicals have reached a record high.

Chlorofluorocarbons are entirely man-made gases used in a variety of applications, including refrigeration, air conditioning or as chemical solvents. They have been increasingly regulated by a series of international treaties since the 1980s. The 1987 Montreal protocol, which has been unanimously ratified, restricted the release of Chlorofluorocarbons to the atmosphere where they contribute to the destruction of the ozone layer: a region high up in the stratosphere which absorbs harmful ultraviolet radiation and protects life below.

The goal of the Montreal protocol was to induce a decline in the atmospheric Chlorofluorocarbons concentration through controlling and increasingly restricting, the production of these chemicals. This has worked well for many ozone-depleting substances, which is why the ozone layer is slowly recovering. And so the recent increase in atmospheric concentrations of five Chlorofluorocarbons is quite surprising.

Our findings, while worrying, should be considered an early warning. The impact of all five Chlorofluorocarbons on the recovery of the ozone layer is still small. Nevertheless, we do not fully understand where they are coming from, so this could change in the future, and we should not ignore the cumulative effect...

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