Joint written evidence submitted by Adam J L Harris, Nigel Harvey, Leonard A Smith, David A Stainforth, Erica Thompson (CLC018)

To increase public trust in the results of climate science, we recommend that the uncertainties inherent in climate forecasts be made explicit. In cases where these uncertainties can be legitimately expressed as probabilities, we suggest that use of a dual verbal/numerical format for expressing uncertainty (e.g., ‘likely (65-80%)’) will enhance communicative effectiveness. We also propose use of the verbal confidence scale developed by the Intergovernmental Panel on Climate Change for their Fifth Assessment Report, especially important in cases where there are underlying problems in expressing the uncertainties as probabilities. Finally, we see the media as having a role in helping the public understand how forecasts are generated from models of the climate and, more particularly, the degree to which diversity in outputs from these models reflects uncertainty in those forecasts.