1. T. L. Anderson is at the Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, WA 98195, USA.
2. R. J. Charlson is in the Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USA.
3. S. E. Schwartz is in the Atmospheric Sciences Division, Brookhaven National Laboratory, Upton, NY 11973, USA.
4. R. Knutti is in Climate and Environmental Physics, Physics Institute, University of Bern, CH-3012 Bern, Switzerland.
5. O. Boucher is in the Laboratoire d'Optique Atmosphérique, CNRS, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex
6. France. H. Rodhe is in the Department of Meteorology, Stockholm University, SE-10691 Stockholm, Sweden.
7. J. Heintzenberg is in the Institute for Tropospheric Research, D-04318 Leipzig, Germany.