Chemical Loss of Polar Ozone: Present Understanding and Remaining Uncertainties Ross Salawitch, Tim Canty, Derek Cunnold, Marcel Dorf, Katja Frieler, Sophie Godin-Beekman, Michael Newchurch, Klaus Pfeilsticker, Markus Rex, Rick Stimpfle, Martin Streibel, Peter von der Gathen, Debra Weisenstein, Eun-Su Yang 1. Introduction and Overview 2. Is Antarctic Ozone Recovering ? 3. Do We Understand Chemical Ozone Loss Rates ? 4. Arctic Ozone Loss and Climate Change ?