Using Maps of City Analogues to Display and Interpret Climate Change scenarios and their uncertainty

We describe a method to represent the results of climate simulation models with analogues. An analogue to a city A is a city B whose climate today represents A's simulated future climate. Climates were characterized and compared non-parametrically, using the 30-years distribution of three indicators : Aridity Index, Heating Degree Days and Cooling Degree Days. Analogy was evaluated statistically with the two-samples Kolmogorov-Smirnov test, generalized to 3 dimensions. We looked at the climate of 12 European cities at the end of the century under an A2 climate change scenario. We used two datasets produced with high-resolution regional climate simulation models from the Hadley Center and Meteo France. Climate analogues were generally found southward of present locations, a clear warming trend even if much model and scenario uncertainty remains. Climate analogues provide an intuitive way to show the possible effects of climate change on urban areas, offering a holistic approach to think about how cities adapt to different climates. Evidence of its communication value comes from the reuse of our maps in teaching and in several European mass-media.