Comparison of different sources of uncertainty in climate change impact studies in Great Britain

The paper assesses the range of changes from a comprehensive set of scenarios describing uncertainties due to climate modelling and climate projections for the 2080s. The study focuses on the mean annual flow ANN and the low flow regime indicator Q95. The changes are represented by confidence bands including 90% of the future simulations and are compared with estimated variations in ANN and Q95 due to natural climatic variability. The climatic projections include uncertainty in future emissions of greenhouse gases, in modelling global climate and in downscaling methodologies, while the natural variability is assessed through data resampling. Results are analysed to assess which of the considered uncertainties is largest for one British test catchment, and to provide guidance for incorporating uncertainty in future impact studies.