1. J. Rozema is in the Department of Systems Ecology, Vrije Universiteit, 1081 HV Amsterdam, Netherlands.
2. B. van Geel is at the Institute for Biodiversity and Ecosystems Dynamics, University of Amsterdam, 1090 GB Amsterdam, Netherlands.
3. L. O. Björn is in the Department of Plant Physiology, Lund University, S-22100 Lund, Sweden.
4. J. Lean is at the E. O. Hulburt Center for Space Research, Washington, DC 20375, USA.
5. S. Madronich is at the Atmospheric Science Division, Boulder, CO 80307, USA.