1. Geosciences Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093
2. Earth Observing Laboratory, National Center for Atmospheric Research, Boulder, CO 80307
3. Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80307
4. Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama 236-0001, Japan
5. Max Planck Institute for Biogeochemistry, Jena 07745, Germany
6. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109
7. Global Monitoring Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80309