Abstract
Our understanding of mankind’s influence on the climate is largely based on computer simulations1,2. Model output is typically averaged over several decades3 so that the anthropogenic climate change signal stands out from the largely unpredictable ‘noise’ of climate variability. Similar averaging periods (30-year) are used for regional climate projections4,5,6 to inform adaptation. According to two such projections, UKCIP02 (ref. 4) and UKCP09 (ref. 6), the UK will experience ‘hotter drier summers and warmer wetter winters’7,8 in the future. This message is about a typical rather than any individual future season, and these projections should not be compared directly to observed weather as this neglects the sizeable contribution from year-to-year climate variability. Therefore, despite the apparent contradiction with the messages, it is a fallacy to suggest the recent cold UK winters like 2009/2010 disprove human-made climate change9. Nevertheless, such claims understandably cause public confusion and doubt10. Here we include year-to-year variability to provide projections for individual seasons. This approach has two advantages. First, it allows fair comparisons with recent weather events, for instance showing that recent cold winters are within projected ranges. Second, it allows the projections to be expressed in terms of the extreme hot, cold, wet or dry seasons that impact society, providing a better idea of adaptation needs.
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Change history
06 August 2015
In the version of this Letter originally published, the use of UK versus England/Wales was inconsistent. The text has been amended to clarify throughout. These errors have been corrected in all versions of the Letter.
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Acknowledgements
We would like to thank L. Kendon for encouraging us to think about this issue. We would also like to thank S. Belcher, B. Booth, S. Brown, K. Humphrey, V. Pope, A. Scaife, R. Street and colleagues at the Isaac Newton Workshop on ‘Mathematical and statistical approaches to climate modelling and prediction’ and, in particular, J. Murphy for comments. This work was supported by the Met Office Hadley Centre Climate Programme—DECC/Defra (GA01101). We acknowledge the international modelling groups for providing their data for analysis, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) for collecting and archiving the model data, the JSC/CLIVAR Working Group on Coupled Modelling (GCM) and their Coupled Model Intercomparison Project (CMIP) and Climate Simulation Panel for organizing the model data analysis activity, and the IPCC WG1 TSU for technical support. The IPCC Data Archive at Lawrence Livermore National Laboratory is supported by the Office of Science, US Department of Energy.
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D.M.H.S. and G.R.H. both conceived the method. D.M.H.S. coded up the solution by modifying the original code of G.R.H. and D.M.H.S. which was used to produce UKCP09. D.M.H.S. drafted the initial version of the manuscript and Supplementary Information and made the plots. Both authors discussed the results and implications, and commented on the manuscript at all stages.
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Sexton, D., Harris, G. The importance of including variability in climate change projections used for adaptation. Nature Clim Change 5, 931–936 (2015). https://doi.org/10.1038/nclimate2705
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