Ozone layer recovery

ON the basis of recent measurements, it has been concluded that the ozone layer over the North Pole should recover by the end of the century. This means that the Montreal Protocol has been effective and is good news for the ozone layer above the Arctic. This is one of the main findings of the European Union project RECONCILE, which was completed in February.

Scientists from Jülich, Germany, and their colleagues from 35 research institutions and universities in 14 countries spent four years investigating the chemical process of ozone depletion. By improving existing climate models, the scientists were able to predict more reliably how the ozone layer would develop in future and on the possible consequences of climate change for the stratosphere.

But even if the ozone layer recovers, climate change could alter the underlying conditions, according to Marc von Hobe from Jülich Research Centre (Forschungszentrum Jülich), which coordinated RECONCILE. Climate change could alter the temperature, circulation patterns and chemical composition in the stratosphere.

This also influences the ozone layer, which in turn has a bearing on temperature. But more interestingly, some ventures to mitigate climate change could have a negative impact on the ozone layer. One example is the so-called geoengineering, which is technologically intervening in the geochemical or biogeochemical processes of the earth.

The study also confirmed the role of chlorine on the ozone layer, thus refuting the conclusions of the study published in 2007 which indirectly questioned the role of chlorofluorocarbons (CFCs) and the Protocol.

RECONCILE has successfully answered some of the open questions regarding ozone loss and demonstrated that besides chlorine no additional chemical mechanisms played a decisive destructive role. Analyses of air samples at the University of East Anglia and the University of Frankfurt as part of the project showed a clear decrease in stratospheric chlorine. Although these compounds remain in the atmosphere longer than previously thought, the scientists expect the ozone layer to recover by the end of the century.