Abstract
Communicating information about consistency in projections is crucial to the successful understanding, interpretation and appropriate application of information from climate models about future climate and its uncertainties. However, mapping the consistency of model projections in such a way that this information is communicated clearly remains a challenge that several recently published papers have sought to address in the run up to the IPCC AR5. We highlight that three remaining issues have not been fully addressed by the literature to date. Allen and Ingram (Nature 419:224, 2002) While additional information about regions where projected changes in rainfall are not ‘statistically significant’ can provide useful information for policy, the spatial scale at which changes are assessed has a substantial impact on the signal-to-noise ratio, and thus the detectability of changes. We demonstrate that by spatially smoothing the model projections we can provide more information about the nature of the signal for larger regions of the world. Christensen et al. (2007) Combining information about magnitude, consistency and statistical significance of projected changes in a single map can cause reduced legibility. We demonstrate the difficulty in finding a ‘universal’ method suitable for a wide range of audiences DEFRA (2012) We highlight that regions where projected changes in average rainfall are not statistically significant, changes in variability may still cause significant impacts. We stress the need to communicate this effectively in order to avoid mis-leading users. Finally, we comment on regions of the world where messages for users of climate information about ensemble consistency have changed since AR4, noting that these changes are due largely to changes in the methods of measuring consistency rather than any discernable differences between the CMIP3 and CMIP5 ensembles.
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Acknowledgments
This work was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups for producing and making available their model output. For CMIP the U.S. Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. We are also grateful to Jamie Kettleborough, Ian Edmond and Emma Hibling at the Met Office Hadley Centre for developing tools which have allowed us to download and access this data easily. We thank Ben Booth for useful comments and encouragement in developing this manuscript.
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McSweeney, C.F., Jones, R.G. No consensus on consensus: the challenge of finding a universal approach to measuring and mapping ensemble consistency in GCM projections. Climatic Change 119, 617–629 (2013). https://doi.org/10.1007/s10584-013-0781-9
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DOI: https://doi.org/10.1007/s10584-013-0781-9