1. Department of Earth and Atmospheric Sciences, Saint Louis University, Saint Louis, Missouri;
2. Department of Chemistry, University of Colorado Boulder, Boulder, Colorado;
3. Center for Industrial Ecology, Yale University, New Haven, Connecticut;
4. Fenner School of Environment and Society, Australian National University, Canberra, Australian Capital Territory, Australia;
5. Institute of Environmental Physics/Institute of Remote Sensing (IUP/IFE), University of Bremen, Bremen, Germany;
6. NOAA/Aeronomy Laboratory, Boulder, Colorado;
7. Department of Chemistry, University of Oxford, Oxford, United Kingdom