Atmos. Chem. Phys. Discuss., 10, 19005-19029, 2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Evidence for the effectiveness of the Montreal Protocol to protect the ozone layer
J. A. Mäder1, J. Staehelin1, T. Peter1, D. Brunner1,*, H. E. Rieder1, and W. A. Stahel2
1Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
2Seminar for Statistics, ETH Zurich, 8092 Zurich, Switzerland
*now at: EMPA – Material Science and Technology, Duebendorf, Switzerland

Abstract. The release of man-made ozone depleting substances (ODS, including chlorofluorocarbons and halons) into the atmosphere has lead to a near-linear increase in stratospheric halogen loading since the early 1970s, which started to level off after the mid-1990s and then to decline, in response to the ban of many ODSs by the Montreal Protocol (1987). We developed a multiple linear regression model to test whether this has already a measurable effect on total ozone values observed by the global network of ground-based instruments. The model includes explanatory variables describing the influence of various modes of dynamical variability and of volcanic eruptions. In order to describe the anthropogenic influence a first version of the model contains a linear trend (LT) term, whereas a second version contains a term describing the evolution of equivalent effective stratospheric chlorine (EESC). By comparing the explained variance of these two models we evaluated which of the two terms better describes the observed ozone evolution. For a significant majority of the stations, the EESC proxy fits the long term ozone evolution better than the linear trend term. Therefore, we conclude that the Montreal Protocol has started to show measurable effects on the ozone layer about twenty years after it became legally binding.

Citation: Mäder, J. A., Staehelin, J., Peter, T., Brunner, D., Rieder, H. E., and Stahel, W. A.: Evidence for the effectiveness of the Montreal Protocol to protect the ozone layer, Atmos. Chem. Phys. Discuss., 10, 19005-19029, doi:10.5194/acpd-10-19005-2010, 2010.
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