CFCs in the atmosphere have hit record highs but researchers are unsure where they’re coming from

Scientists said on 3 April that five man-made chlorofluorocarbons (CFCs) have hit record levels in the atmosphere. The milestone comes despite the Montreal Protocol banning the five CFCs in 1987. The study said the increase was possibly due to leakage during the production of CFC alternatives.

An early warning

According to the study published in the journal Nature Geoscience, the five CFCs increased rapidly in the atmosphere from 2010 to 2020. They reached record-high levels in 2020. Although at current levels they don’t threaten the ozone layer’s recovery, the gases are joining other emissions in heating the atmosphere. CFCs are potent greenhouse gases (GHGs) that trap heat up to 10,000 times more efficiently than carbon dioxide.

The study analysed five CFCs with no or few current uses, beginning at the point of their total global phase-out in 2010. It found that, in 2020, all five gases were at their highest abundance since direct measurements began.

Those emissions have so far resulted in a modest impact on the ozone layer and slightly larger climate footprint, according to co-author Luke Western of Bristol University and the Global Monitoring Laboratory. They are equivalent to the 2020 CO2 emissions of Switzerland. That’s about 1%t of the total GHG emissions of the United States. However, if the rapid upward trend continues, their impact will increase. The researchers called their findings “an early warning” of a new way in which CFCs are endangering the ozone layer.

Unknown sources

The emissions are likely due to processes that are not subject to the current ban and unreported uses. This included the production of chemicals that are meant to replace CFCs, including hydrofluorocarbons (HFOs). Manufacturing HFOs can release CFCs as a by-product.

In 2018, scientists discovered that the pace of CFC slowdown had dropped by half from the preceding five years. Evidence in that case pointed to factories in eastern China, the researchers said. Once CFC production in that region stopped, the draw-down appeared to be back on track.

The study said further research was needed to ascertain the precise source of the recent rise in CFC emissions. Nationwide data gaps make it difficult to determine where the gases are coming from, and for some of the CFCs analysed there are no known uses. Western said, however, that:

eradicating these emissions is an easy win in terms of reducing greenhouse gas emissions.

Fellow study co-author Isaac Vimont, of the Global Monitoring Laboratory at the US National Oceanic and Atmospheric Administration, said:

If you are producing greenhouse gases and ozone-depleting substances during the production of… next-generation compounds, then they do have an indirect impact on the climate and the ozone layer

Exacerbating the climate crisis

In the 1970s and 1980s, CFCs were widely used as refrigerants and in aerosol sprays. However, the discovery of a hole in the ozone layer over Antarctica as a result of their use led to the Montreal Protocol pushing to eliminate them. After it entered into force, global concentrations of CFCs declined steadily.

CFCs were largely replaced by hydroflurocarbons (HFCs). However, a 2016 amendment to the Montreal Protocol aims to ‘phase down’ HFCs by 2050. Although they are harmless to the ozone layer, HFCs are considered GHGs. As a result, they play a part in speeding up the climate crisis. At the same time, however, some scientists believe the climate crisis is playing a part in extending the opening of the hole in the ozone layer above Antarctica.

Featured image via NASA on the Commons/Flickr

Additional reporting by Agence France-Presse