Urban climate in km-scale climate simulations under historical periods and future scenarios

We analyse two 30-year long global, fully coupled Earth-System simulations at a spatial resolution of around 9 km. The first simulation covers the recent decades from 1990-2020, while the second simulates a future SSP3-7.0 scenario, usually leading to one of the warmest future climates, during the period 2020-2050. These simulations are the first multi-decadal simulations at kilometre-scale resolution with an explicit representation of urban areas. These unique simulations enable us to study the two-way interactions between cities and regional climates globally, the evolution of urban climates across the recent decades, as well as the projected changes in the period 2020-2050 for cities worldwide.

The accuracy and associated uncertainties of the urban climate representation were assessed by comparing present-day simulations against surface temperature observations from LSA-SAF over a wide range of major cities. This data set provides relevant observations at a high spatio-temporal resolution and covers most of the globe. It therefore allows for a spatially consistent validation of the thermal impact of urban areas. This analysis is of particular interest for regions with scarce in-situ surface observations and/or limited regional/local simulations.  

We explore the classification of cities with differing characteristics, e.g.  regional topography, morphology or local climates, for a comprehensive global analysis of urban climates. We also investigate past and future trends for these city groups and attempt to classify urban areas around the globe in terms of expected shifts in climate.