GSI Seminar Series – Dr Will Seviour: Stratospheric Ozone Depletion and its Impact on Climate

Taken from GSI Seminar coordinator Daneen Cowling’s Blog 

Today (03/02/2021) saw the second seminar in the GSI Spring Seminar Series of 2021. We hosted speaker Dr Will Seviour, a senior lecturer at the University of Exeter Department of Mathematics, and the GSI.

Dr Saviour is a relatively new academic at Exeter, but brings with him a wealth of experience and specialism in Ozone and large-scale Earth System dynamics from the University of Oxford, John Hopkins University and University of Bristol. Dr Seviour’s work now looks into climate and extreme weather consequences of Arctic warming, and coupled dynamics of Southern Ocean dynamics – the topic of his talk.


Dr Seviour introduced the importance of ozone and it’s role as a planetary boundary – central to a habitable Earth. Ozone was also shown to have practical importance to the success of the sustainable development goals.

However, Dr Seviour soon delved into the consequences of the current state of ozone attention, it’s depletion. Ozone Depletion Substances (ODS) e.g. CFC’s, were shown to have had a strong control on Ozone, trending with their emission and eventual regulation. They were also shown to be powerful greenhouse gases.

Dr Seviour invited the audience to an interactive quiz, to rank where ODS sit amongst other common greenhouse gases (CO2, N2O and CH4) in radiative forcing. This produced the surprising result that ODS were only second to CO2 in their forcing, accounting for a 1/3 of warming effects of CO2 since the mid 20th Century. This strength was also identifiable in warming impacts – even by simulating models with only the forcing of ODS (and not other greenhouse gases), trends in Arctic melting were still observable. The focus then shifted to the south pole; why there is more ozone depletion over Antarctica and how it’s variable with atmospheric dynamics.


The ozone situation definitely wasn’t doom and gloom, as Dr Seviour then discussed the long term ‘healing’ trends being observed and modelled. Since a reduction in CFCs from the Montreal Agreement, and an assessment every 4 years on ODS, ozone depletion has started showing signs of recovery. But when would ozone return back to 1960 levels? Dr Seviour again invited the audience to an interactive quiz, to give their best estimates of the return for global and Antarctic levels of ozone. Majority of the guesses were around the current predictions of 2060 and 2090 respectively.

Thanks to a warming climate, the recovery may be even faster due to changes in stratospheric circulation. But, true to the Earth system, these changes will not be linear. Dr Seviour explained that this would lead to a cooling Southern Ocean, which would expand sea ice around Antarctica, then shift polar jets. Yet, there would still likely be a long term warming trend – driven by upwelling.


Dr Seviour’s talk left us with a new appreciation with the importance of ozone, and it’s climate control – whether that be through it’s greenhouse gas equivalent forcing, or the atmospheric dynamics it influences.

Several interesting questions followed, which Dr Seviour answered in detail as well as directing to follow-up resources.

You can watch Dr Seviours full talk here

To learn more about Dr Seviours work, you can view his publications and research projects on his personal website

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