Two chimneys spew smoke into a grey sky.

Five CFCs are increasing in concentration, but researchers aren't sure where two of them are coming from. Image © Eskoma/Shutterstock

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Mystery emissions of ozone-damaging gases are fuelling climate change

It's not just carbon dioxide that causes climate change.

Chlorofluorocarbons, or CFCs, are a group of chemicals that were widely banned because of their effects on the ozone layer. Unknown sources are emitting more of these compounds, which are also powerful greenhouse gases.

Levels of some ozone-damaging gases are on the rise, despite a global ban on their production.

Chlorofluorocarbons were gases formerly used in a variety of products, from refrigerators to aerosols and home insulation foam. However, in the 1980s researchers realised that these compounds had opened a hole in the Earth's ozone layer, which protects life from UV radiation.

A ban was introduced under the Montreal Protocol, with production of the gases meant to be phased out entirely by 2010. However, new research reveals that levels of five CFCs rose rapidly in the past decade, likely being produced as byproducts during industrial processes.

While the gases are unlikely to have a major impact on the ozone layer, they may derail efforts to limit global warming to 1.5⁰C.

Dr Luke Western, the lead author of the study published in Nature Geosciences, says, 'If emissions of these CFCs continue at current levels, any delay to the recovery of the ozone hole will probably be very small.'

'However, they remain potent greenhouse gases, and in 2020 their warming effect is equivalent to the annual carbon dioxide emissions of a country like Switzerland. This is a substantial impact, and mitigating the emissions of these gases will have a significant effect on the course of climate change.'

The researchers have called for more CFC monitoring around the globe to rapidly identify and tackle any further emissions.

Delegates to the 28th Meeting of Parties to the Montreal Protocol listen to a speech by John Kerry.

The introduction of the Montreal Protocol has vastly reduced the emissions of most CFCs. Image © U.S. Department of State, licensed under Public Domain via Flickr

What are CFCs?

CFCs are a group of gases which all contain the elements chlorine, fluorine and carbon. These compounds accelerate the breakdown of ozone, and can remain in the atmosphere for many years.

Their effect was so prominent that they caused a hole to open in the ozone layer over Antarctica, which led to rapid international action. The countries of the world universally agreed to adopt the Montreal Protocol in 1987 and begin phasing out these gases.

In 2010, all dispersive uses of CFCs, or any use where the gases would eventually end up in the atmosphere, were banned. These restrictions have helped the ozone layer begin to heal, and it is predicted to fully recover by the middle of the century.

Despite the ban, however, some CFCs are still being emitted into the atmosphere. Emissions of a gas known as CFC-11 increased by around a quarter between 2012 and 2018, which was later attributed to it still being used for home insulation.

The new study identifies five more gases which are becoming more common in the atmosphere, following reports from CFC monitoring groups around the world.

Dr Isaac Vimont, a researcher at the Global Monitoring Laboratory and co-author of the study, says, 'These measurements were made by several groups around the world with different methods, but we all got the same story out of it. This shows that real changes are taking place in the atmosphere.'

'We don't know directly where these emissions are coming from geographically, but it's likely they come from outside the USA and Europe because these areas have well-developed monitoring networks in place.'

Three of the gases (CFC-113a, 114a and 115) are associated with the production of other chemicals. If a reaction is incomplete, or the process isn't completely sealed, then this can lead to these CFCs entering the atmosphere.

The increase in the other detected gases, such as CFC-13 and CFC-112a, are currently unexplained. While small amounts are produced during processes like aluminium smelting, there's much more entering the atmosphere than can be explained by this process.

Dr Stefan Reimann, a co-author from the Group for Climate Gases, adds, 'There have never been any big uses of CFC-13, and we don't really know where it's coming from, which is a bit scary.'

An image showing the ozone hole over Antarctica, with the hole highlighted in blue.

The hole in the ozone layer (shown in blue) continues to recover following the introduction of the Montreal Protocol. Image © GSFC/NASA, licensed under Public Domain via NASA Images

What effect are these CFCs having on the atmosphere?

While any amount of CFCs will have an effect on the ozone layer, the effect of the detected releases is fortunately small. The researchers estimate that the collective emissions of all five CFCs in the study will cause the loss of just 0.002% of ozone high in the atmosphere.

However, as greenhouse gases, these CFCs can still pose a risk to health by contributing to climate change. Compared to the same amount of carbon dioxide, gases like CFC-114a will trap thousands of times more heat.

Even the successors of CFCs, which don't deplete the ozone layer, have a very high global warming potential. As a result, the use of these gases, called HFCs, is being reduced in favour of another class of compounds.

Producing any of these compounds tends to involve the use of CFCs somewhere in the process. As a result, it is likely that CFCs will continue to enter our atmosphere through leaks for years to come.

The researchers are calling for updates to the Montreal Protocol to eliminate these leaks as much as possible and reduce the ongoing effects of CFCs.

'There is a danger that if things go further than current levels then there might be a significant impact,' Stefan says. 'These measurements are an early warning that CFC emissions could increase by previously unrecognised mechanisms, and need to be monitored closely.'