Emissions from the banned ozone killers are on the rise – and no one knows why

In fact, combating the ozone hole is one of the rare success stories in global climate policy: although it has not yet disappeared, the vital upper stratospheric ozone layer has recovered significantly according to recent studies and is on its way to full recovery. This was ensured by the Montreal Protocol, which came into force in 1989 and required signatory states to reduce and ultimately eliminate emissions of the chemicals responsible for ozone depletion.

These are chlorofluorocarbons (CFCs), which have been produced industrially since 1929 and have played an important role in refrigeration technology, as a propellant in aerosol cans, in the manufacture of foam or as a cleaning agent and solvent. However, these odorless and intrinsically non-toxic gases rise to the stratosphere, where they split ozone molecules at very low temperatures and under the influence of sunlight. As greenhouse gases, they also contribute to global warming.

However, it is now becoming clear that emissions of five ozone-depleting chemicals have increased significantly despite these far-reaching bans. This is the surprising conclusion of a new study involving the US National Oceanic and Atmospheric Administration (NOAA), the University of Bristol and other research institutes, as well as the Swiss Federal Laboratories for Materials Testing and Research (EMPA). Based on measurements at 14 locations around the world, including the Jungfraujoch, the researchers show that the concentration of five CFCs (CFC-13, CFC-112a, CFC-113a, CFC-114a and CFC-115) in the atmosphere has increased.

The manufacture of the five CFCs, of which hardly any applications are currently known, will be banned in 2010 for most applications. Nevertheless, their emissions increased rapidly in subsequent years. According to EMPA, some CFCs are produced during the production of ozone-friendly substitutes. The emissions from such by-products and intermediates are permitted under the Montreal Protocol, but are contrary to its objectives.

The increased emissions of three of the CFCs studied (CFC-113a, CFC-114a and CFC-115) can be attributed, at least in part, to their role in the production of two common substitutes. These are mainly used in refrigeration and air conditioning systems. The researchers fear that the production of such new generation substitutes will increase further in the future – and with it the emission of CFCs as a by-product.

In contrast, the reasons for the increase in emissions of the other two CFCs (CFC-13 and CFC-112a) remain largely a mystery. “We are not aware of any current hydrofluorocarbon chemical process in which these two substances occur as an intermediate or by-product,” emphasizes Empa’s Martin Vollmer, one of the study’s co-authors. The researchers could not determine where the emissions come from; Although they documented their global increase, they were unable to identify specific source regions due to a lack of measurement data.

According to the study, the emissions currently do not significantly jeopardize the recovery of the ozone layer. However, this increase could change this. Because CFCs also act as potent greenhouse gases, they also have a negative impact on climate change.

Taken together, their emissions would correspond to CO₂emissions from a smaller developed country like Switzerland in 2020, study leader Luke Western, a research fellow at the University of Bristol and a researcher at NOAA’s Global Monitoring Laboratory (GML), said in a statement from the University of Bristol. That equates to about one percent of total greenhouse gas emissions in the United States. To achieve the goals of the Montreal Protocol, it may therefore be necessary to tighten it up.

(mr/sda)