Amy H Butler, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, United States; Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO, United States, Antara Banerjee, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States; National Oceanic and Atmospheric Administration / Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO, United States, Lorenzo M Polvani, Columbia University, Department of Applied Physics and Applied Mathematics, New York, NY, United States and Alan Robock, Rutgers University, New Brunswick, NJ, United States