Scot M Miller, Johns Hopkins University, Department of Environmental Health and Engineering, Baltimore, MD, United States, Benjamin R Miller, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, Olin Shipstead, Johns Hopkins University, Department of Environmental Health and Engineering, Balitmore, MD, United States, Leyang Feng, Johns Hopkins University, Baltimore, United States, Arlyn E Andrews, NOAA/ESRL, Global Monitoring Division, Boulder, CO, United States, Joshua Simon Benmergui, Harvard University, Cambridge, MA, United States and Edward J Dlugokencky, NOAA/ESRL Global Monitoring Division, Boulder, CO, United States