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New method to assess impact of substances that damage ozone layer developed by University of Cambridge and Leeds researchers

A new method for assessing the impact of substances that damage the ozone layer has been developed by University of Cambridge researchers and colleagues.

The method - known as the Integrated Ozone Depletion (IOD) metric - provides a tool for policymakers and scientists to measure the effects of unregulated emissions of substances that deplete the ozone layer, and evaluate the effectiveness of protection measures.

The ozone layer has been depleted by CFCs
The ozone layer has been depleted by CFCs

Found in the region of the Earth’s atmosphere known as the stratosphere, the ozone layer is an important barrier against the sun’s harmful ultraviolet rays.

But it was damaged by ozone-depleting gases such as chlorofluorocarbons (CFCs), which were used in products such as aerosol sprays and refrigerants until they were phased out under the internationally-agreed Montreal Protocol.

Illegal breaches of the treaty, however, still threaten the ozone layer and there is concern over the speed of its recovery.

The IOD looks at three elements: the strength of any new emissions, how long they will remain in the atmosphere and how much ozone is chemically destroyed by them.

It was developed by researchers at the National Centre for Atmospheric Science at the University of Cambridge and the National Centre for Earth Observation at the University of Leeds.

Professor John Pyle, from the National Centre for Atmospheric Science and the University of Cambridge, has dedicated his career to studying the depletion of ozone in the stratosphere and helped to develop the Montreal Protocol.

“Following the Montreal Protocol, we are now in a new phase - assessing the recovery of the ozone layer,” said Prof Pyle, from Cambridge’s Yusuf Hamied Department of Chemistry, who is lead author of a paper on the subject published in Nature.

“This new phase calls for new metrics, like the Integrated Ozone Depletion - which we refer to as the IOD. Our new metric can measure the impact of emissions - regardless of their size. Using an atmospheric chemistry computer model, we have been able to demonstrate a simple linear relationship between the IOD, the size of the emissions and the chemical lifetimes. So, with knowledge of the lifetimes, it is a simple matter to calculate the IOD, making this an excellent metric both for science and policy.

“The Montreal Protocol is successfully protecting the ozone layer, but there is increasing evidence to suggest the ozone hole is recovering slower than expected. The IOD will be very useful for monitoring ozone recovery, and especially relevant to regulators who need to phase out substances with the potential to chemically destroy ozone.”

A computer model of the atmosphere, the UK Chemistry and Aerosols model (UKCA), was used to develop the metric. It was created by the National Centre for Atmospheric Science and the Met Office to calculate future projections of important chemicals, such as ozone in the stratosphere.

Co-author Dr Luke Abraham, also from the University of Cambridge, said: “We have used the UKCA model to develop the IOD metric, which will enable us to estimate the effect of any new illegal or unregulated emissions on the ozone layer. In the UKCA model we can perform experiments with different types and concentrations of CFCs, and other ozone-depleting substances.

“We can estimate how chemicals in the atmosphere will change in the future, and assess their impact on the ozone layer over the coming century.”

The research was supported in part by the Natural Environment Research Council (NERC), part of UK Research and Innovation (UKRI).

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