Atmospheric Chemistry, with a focus on:
The impact of UV radiation on the chemistry of the atmosphere
Atmospheric particles (aerosols) in both clean and urban atmospheres.
As a result of this, I am a lead scientist (Solar Radiation) at the Cape Grim Baseline Air Pollution Station in Northwest Tasmania. This is one of the premier atmospheric measurement sites globally.
I am also a member of the "Environmental Effects Assessment Panel", which was established as part of the Montreal Protocol to protect the Ozone layer. Three such panels were established to provide scientific and engineering expertise to the countries who signed the agreement.