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Theodore G. Shepherd

Professor, Department of Physics

Ozone depletion and climate changeShepherd image

The stratospheric ozone layer has been depleted by anthropogenic emissions of halogenated compounds (mainly CFCs). Thanks to the Montreal Protocol, these emissions have largely stopped. However because of the long atmospheric lifetimes of these compounds, the ozone layer is expected to recover only slowly, over the next half-century. During this time climate change will affect ozone recovery; but equally, ozone depletion and recovery affects climate. It is important to understand and separately attribute atmospheric changes due to greenhouse gases and ozone-depleting substances.

My research focuses on the use of comprehensive atmospheric models to understand the coupling and interaction between ozone depletion and climate change. In order to establish confidence in the models, we study their ability to represent key processes and feedbacks in a physically consistent manner, which involves theoretical analysis. We also compare the models with measurements in a process-oriented fashion. This further allows for a better understanding of measurement representativeness and errors, and the design of measurement strategies. In this way, measurements and models work hand-in-hand toward a better understanding of the atmosphere.

My research group plays a central role in a major national collaborative activity focused on these themes called the Canadian SPARC Programme, which involves a partnership with Environment Canada and the Canadian Space Agency.

To learn more about my research, please visit

To learn more about C-SPARC, please visit