Environmental sciences: Monitoring ozone recovery

A new metric to monitor ozone recovery and evaluate the impact of illegal or unregulated emissions of ozone depleting substances on the ozone layer is described in a Nature paper. The new metric may provide a useful additional tool for policy makers and scientists to assess the impact of specific ozone depleting substances.

The Montreal Protocol — an international treaty designed to protect the ozone layer — has led to a decline in atmospheric levels of ozone depleting substances, and we have now entered a new phase of ozone recovery. A new metric to monitor ozone recovery, illegal breaches of the Protocol and emissions from other substances is necessary to highlight the impacts on the ozone layer, as previous metrics remain ambiguous.

John Pyle and colleagues propose an integrated ozone depletion metric to indicate the impact of any new emission on the ozone layer. By considering the emission strength and how long it persists in the atmosphere or stratosphere, their metric also provides information about how the ozone layer might recover from specific emissions and is simpler to calculate than previous metrics.

The authors suggest that for gases with known lifetimes in the atmosphere, the integrated ozone depletion metric provides a simple means of assessing the impact and importance to policy objectives, of any given emission scenario on the ozone.