1. Environmental Change Institute, Oxford University Centre for the Environment, South Parks Road, Oxford OX1 3QY, UK.
2. College of William and Mary, Williamsburg, VA 23187, USA.
3. Met Office Hadley Centre, Exeter EX1 3PB, UK.
4. Conservation International, Washington, DC 20036, USA.
5. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332–0340, USA.