Modelling the relative impact of land-use change and global climate change on the climate in cities

It is known from global climate ensemble projections that both global warming and the increasing extreme weather conditions including heat waves and pluvial flooding will put increasing pressure on the livability of cities. At the same time, urban heat island intensities are expected to increase because of the unrestrained urban expansion, which makes cities the 'hotspots' of climate change. This not only implies severe health hazards for the many urban dwellers, it also leads to increased energy consumption, damage of city's infrastructure, and hypothecates the urban environmental health. We investigate the relative impact of urban land-use change and global climate change on the increased temperatures and extreme precipitation in cities at the second half this century. Therefore, urban-climate simulations with COSMO-CLM coupled to TERRA_URB at 2.8km resolution over Belgium are cascade-nested in EC-EARTH (GCM) for the climate of the recent past (2000-2010) and for future climate projections (2060-2070). The regional climate model accounts for urban land-use change for Belgium towards 2060 based on projections with 'Ruimtemodel Vlaanderen'. We further address the synergy between urban heating and global climate change. Hereby, we investigate how the frequency and intensity of heat waves (+), the local changes in atmospheric radiative transfer by greenhouse gases (-), changes in precipitation (+/-), but also the urban expansion (+) and increased cooling demands (+) affect heat island intensities in Belgium. In order to account for urban climate with a broad-risk assessment approach, we investigate the relation between urban heat island intensities and the frequencies of circulation weather types or the percentiles from the temporal temperature distributions.status: publishe