1. Laboratory for Atmospheric and Space Physics, Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80303, USA.
2. Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO 80307, USA.
3. Department of Environmental Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
4. Federation of American Scientists, 1112 16th St., N.W. Suite 400, Washington, DC 20036, USA.
5. Natural Resources Defense Council, 40 West 20th St., 11th Floor, New York, NY 10011, USA.
6. Department of Physics, University of Colorado, Boulder, CO 80309-0390, USA.
7. School of Earth, Environmental, and Marine Sciences, University of Texas Rio Grande Valley, Port Isabel, TX 78597, USA.
8. Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309-0450, USA.
9. Department of Atmospheric and Oceanic Sciences, Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309-0450, USA.
10. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA.