1. National Center for Atmospheric Research, Boulder, CO 80307-3000 USA;
2. Scripps Institution of Oceanography, La Jolla, CA 92093-0244 USA;
3. University of Hawaii Honolulu, HI 96822 USA;
4. University of California, Los Angeles, CA 90095-4996 USA;
5. Commonwealth Scientific and Industrial Research Organization, Atmospheric Research Division, Aspendale, Victoria, Australia;
6. Cape Grim Baseline Air Pollution Station, Bureau of Meteorology, Smithton, Tasmania, Australia