I study theoretical aspects of geophysical fluid dynamics, with an emphasis on large-scale atmospheric dynamics. Although atmospheric dynamics is based on fundamental physical laws, this is often forgotten in applications, particularly as the field becomes increasingly specialized. I see my role as helping to ensure that atmospheric dynamics is built on a solid theoretical foundation, which is the ultimate basis for progress in any science.

For my most theoretical research, my underlying philosophy has been to search for fundamental dynamical principles. Most of the theory in our subject has been derived in a rather ad hoc fashion. I seek to provide a systematic foundation for the different approximate model systems used in geophysical fluid dynamics, casting them within a general dynamical framework. In this way, one can derive general theories that transcend any reference to the particularities of a given system, and are instead linked to underlying symmetry properties and conservation laws, as expressed in an abstract (Hamiltonian) language. Examples of this research include nonlinear stability, wave-activity conservation laws, balanced dynamics, and weak-wave models.

The real atmosphere, in all its complexity, obeys the fundamental laws of physics; so too should any model of it, including climate models. My more applied research aims to determine the extent to which climate models provide a physically realistic and reliable description of the atmosphere. My special focus here is on the middle atmosphere, including the ozone layer, and much of my research in this area has been stimulated by my role as PI, from 1992-2013, of a series of funded projects supporting the development and use of the Canadian Middle Atmosphere Model (CMAM). Examples of this research involve transport and mixing, the circulation of the middle atmosphere, and the role of unresolved processes in transferring energy and momentum. Given the importance of climate models in understanding global change, this work has high societal significance: it is essential to understand and improve the reliability of our models.

I have also been heavily involved for some time in international assessments concerning the science of ozone and climate, especially the WMO/UNEP Ozone Assessment. I was honoured to be among the scientists designated by the Intergovernmental Panel on Climate Change as making a significant contribution to the award of the 2007 Nobel Peace Prize to the IPCC. I find the focus on policy-relevant aspects of one's science to be an important stimulant for new research.