The motivation for Dr Harris’ research is to understand the chemical and dynamical factors that determine changes in atmospheric composition: “These are fascinating as scientific problems in their own right and are also important for global environmental issues such as stratospheric ozone depletion and climate change. In the past, scientists have concentrated on relatively short term chemical processes (seconds to weeks); it is now more important than ever to understand how atmospheric composition is influenced by longer-term processes (weeks to years).”