For our analysis we extracted 19 current and future bioclimatic variables from the coordinates of 520 cities around the world, consisting of major administrative capitals and cities with over 1 million inhabitants. These variables reflect the variability in temperature, precipitation as well as their monthly extremes and annual average. Future conditions for the year 2050 were calculated based on the IPCC’s Representative Concentration Pathway RCP4.5, which represents an optimistic scenario where the implementation of mitigation policies will have stabilized CO2 emissions by the mid-century and the mean global temperature will have increased by 1.4° C. Therefore, our results represent a best case scenario.



In a second step, we used a multivariate approach to analyse the climate similarity of all current and future cities. When compared pairwise, we saw that only four out of 19 bioclimatic components are predominant, accounting for more than 85% of the total variation in climate: the temperate seasonality, the minimum temperature in the coldest month, the maximum temperature in the warmest month, the precipitation seasonality, the precipitation of the driest and the wettest month, as well as the temperature diurnal range. Subsequently, all other variables were dropped for the comparison.



In order to achieve our goal of visualizing the climatic changes of cities in the future to enable citizens and decision makers to grasp the impact of climate change, we paired each future city with its three closest current cities based on the dissimilarity value. This allows us to show which city will remain relatively similar to how it is now and which will shift, resembling more the current climate of another city by 2050. By keeping three cities as a basis for comparison, we ensure that at least one of the three is known to the reader.