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Scientists develop new method to assess ozone layer recovery

A team of NERC-funded researchers at NCEO and NCAS have developed a new method for assessing the impacts of ozone-destroying substances that threaten the recovery of the ozone layer. Published in Nature, their method – the Integrated Ozone Depletion (IOD) metric – provides a useful tool for policymakers and scientists.

The IOD has been designed to provide a straightforward way to measure the effects of unregulated emissions of substances that deplete the ozone layer, and evaluate how effective ozone layer protection measures are.

The ozone layer is found in a region of the Earth’s atmosphere known as the stratosphere and acts as an important protective barrier against most of the sun’s harmful ultraviolet rays. Ozone-depleting gases such as chlorofluorocarbons, better known as CFCs, have been phased out under the Montreal Protocol – an international treaty agreed to protect the ozone layer.

The Montreal Protocol has been largely successful, but illegal breaches are jeopardising its efficacy. The IOD indicates the impact of any new emissions on the ozone layer by considering three things: the strength of the emission, how long it will remain in the atmosphere, and how much ozone is chemically destroyed by it.

For environmental protection and human health policies, the IOD represents a simple means of calculating the impact of any given emission scenario on ozone recovery. This new metric has been developed by researchers at the National Centre for Atmospheric Science, National Centre for Earth Observation, University of Cambridge and University of Leeds.

NCEO Atmospheric Scientist, Professor Martyn Chipperfield, said;
‘This metric will provide a simple way for scientists and policymakers to assess the impact of different future emissions on the recovery of the ozone layer. EO data has played a key role in developing the UK chemistry-climate model used to derive this metric, and will be central to verifying that the recovery of the ozone layer is proceeding as expected.’

The IOD metric has been created using a computer model of the atmosphere, called the UK Chemistry and Aerosols model (UKCA). NERC and the Met Office developed the UKCA model to calculate future projections of important chemicals, such as ozone in the stratosphere.

Professor John Pyle CBE, National Centre for Atmospheric Science and University of Cambridge, said;
‘Following the Montreal Protocol, we are now in a new phase – assessing the recovery of the ozone layer. 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 UKCA model enables researchers to perform experiments with different types and concentrations of CFCs, and other ozone-depleting substances. The model can be used to estimate how chemicals in the atmosphere will change in the future, and assess their impact on the ozone layer over the coming century.


Professor Martyn Chipperfield
NCEO Researcher and Professor of Atmospheric Chemistry, University of Leeds