Matthew C Long, National Center for Atmospheric Research, Climate and Global Dynamics, Boulder, CO, United States, Britton B Stephens, National Center for Atmospheric Research, Earth Observing Laboratory, Boulder, CO, United States, Colm Sweeney, NOAA ESRL, Global Monitoring Division, Boulder, CO, United States, Eric A Kort, University of Michigan Ann Arbor, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, Ralph F Keeling, Univ California San Diego, La Jolla, CA, United States and Kathryn McKain, Harvard University, Cambridge, MA, United States