1. Department of Meteorology, The University of ReadingPO Box 243, Earley Gate, Reading RG6 6BB, UK
2. Department of Agriculture, The University of ReadingPO Box 236, Earley Gate, Reading RG6 6AT, UK
3. Met Office, Hadley Centre for Climate Prediction and ResearchFitzroy Road, Exeter, Devon EX1 3PB, UK