1. School of Earth and Environment, University of LeedsLeeds LS2 9JT, UK
2. School of Geographical Sciences, University of BristolUniversity Road, Bristol BS8 1SS, UK
3. Geological Sciences Division, British Antarctic SurveyHigh Cross, Madingley Road, Cambridge CB3 0ET, UK
4. Met Office, Hadley CentreFitzRoy Road, Exeter EX1 3PB, UK