May 16, 2018

expert reaction to research on CFCs

A new study exploring chlorofluorocarbons is published in Nature.

Prof Piers Forster, Director of the Priestley International Centre for Climate at the University of Leeds, said:

“This is atmospheric detective work at its finest. Looking at detailed observations of north-south gradients in gases and combining this with careful atmospheric chemistry modelling, the authors have pinpointed a new source of CFC-11 to east Asia, breaking Montreal Protocol rules. Such detailed forensic analysis really shows how far our science has come. I’m hopeful we can quickly find the source and close it down.”

Prof Joanna Haigh FRS, Professor of Atmospheric Physics at the Grantham Institute, Imperial College London, said:

“This is a worrying result. Chlorofluorocarbons were responsible for the development of the springtime Antarctic ozone hole and a very slow reduction in its area has been cautiously ascribed to the Montreal Protocol beginning to take effect. However, at other locations, observations have suggested an unexplained continuing decline and these now need to be reassessed in the light of this new evidence.

“Perhaps even more serious is the role of CFCs as long-lived greenhouse gases (GHGs): around 20 years ago they were responsible for around 10% of human-induced GHG warming.  An ongoing increase in halocarbons would seriously compromise concerted international efforts on climate change through the reduction of emissions of carbon dioxide and other GHGs.

“An important question which arises from the conclusions of the paper, if correct, is how compliance with international environmental treaties should be monitored or policed. Again with serious implications for future action under the UNFCCC agreement on decarbonisation.”

Prof Martyn Chipperfield, Professor of Atmospheric Chemistry at the University of Leeds, said:

“The observations are puzzling rather than alarming. Atmospheric chlorine levels are still decreasing but more slowly than expected. This will cause some delay in the recovery of the ozone layer from past depletion, but that recovery will still happen. Nevertheless, scientists and policy makes will want to understand the cause of these unexpected CFC-11 emissions.

“This works highlights the importance of maintaining a global observation network to monitor gases such as CFCs. It is reassuring that the observations are able to detect these small, unexpected changes in CFC decay rates and alert us to this issue in good time.”

Dr Paul Young, Atmospheric Scientist at Lancaster University, said:

“The Montreal Protocol has been rightly hailed as our most successful international environmental treaty, so the suggestion that there are possibly continued, unreported emissions of CFCs is certainly troubling and needs further investigation. What this work also demonstrates is that there is tremendous value in the long term observations, both for scientific understanding and assessing whether there is compliance with environmental treaties and legislation.”

* ‘An unexpected and persistent increase in global emissions of ozone-depleting CFC-11’ by Stephen A. Montzka et al. published in Nature on Wednesday 16 May.

Declared interests

Prof Joanna Haigh: “No interests to declare.”

Prof Piers Forster: “No interests to declare.”

Dr Paul Young: “No interests to declare.”

No others received.