1. Cooperative Institute for Research in Environmental Sciences, University of Colorado/National Oceanic and Atmospheric Administration, Campus Box 216, Boulder, CO 80309
2. National Aeronautics and Space Administration, Goddard Space Flight Center, Institute for Space Studies, 2880 Broadway, New York, NY 10025
3. Lamont-Doherty Geological Observatory, Columbia University, Palisades, NY 10964