1. Cooperative Institute for Research in Environmental Science University of Colorado Boulder Boulder Colorado USA
2. Global Monitoring Division, Earth System Research Laboratory National Oceanic and Atmospheric Administration Boulder Colorado USA
3. Institute of Arctic and Alpine Research University of Colorado Boulder Boulder Colorado USA
4. Centre for Isotope Research University of Groningen Groningen Netherlands
5. Alternatives and Emissions Reduction Branch, Stratospheric Protection Division, Office of Atmospheric Programs, Office of Air and Radiation U.S. Environmental Protection Agency Washington District of Columbia USA
6. Environmental Energy Technologies Division Lawrence Berkeley National Laboratory Berkeley California USA
7. Earth Sciences Division Lawrence Berkeley National Laboratory Berkeley California USA
8. Atmospheric and Environmental Research Lexington Massachusetts USA
9. Department of Earth and Planetary Sciences Harvard University Cambridge Massachusetts USA
10. Air Resources Laboratory National Oceanic and Atmospheric Administration College Park Maryland USA