Date: Wednesday 12 December 2012
UKCP09, the latest set of UK Climate Projections, provides probabilistic projections of seasonal and monthly means of several climate variables at 25km resolution over the UK, for seven 30-year periods during the 21st century, for 3 different emissions scenarios. Underpinning the whole product was a Bayesian framework which incorporates different sources of uncertainty: observational uncertainty, parametric uncertainty from an ensemble of perturbed parameter runs, and structural uncertainty using the AR4 ensemble. After a brief introduction to UKCP09, the talk will focus on the Bayesian framework, in particular that part of the method which handles structural uncertainty, outlining its strengths and weaknesses. Finally, a possible way to improve UKCP09 projections will be discussed, in particular how it might help to determine the extent to which structural error affects the credibility of the projections for different variables.