Abstract
A new dynamical downscaling methodology to analyze the impact of global climate change on the local climate of cities worldwide is presented. The urban boundary layer climate model UrbClim is coupled to 11 global climate models contained in the Coupled Model Intercomparison Project 5 archive, conducting 20-year simulations for present (1986–2005) and future (2081–2100) climate conditions, considering the Representative Concentration Pathway 8.5 climate scenario. The evolution of the urban heat island of eight different cities, located on three continents, is quantified and assessed, with an unprecedented horizontal resolution of a few hundred meters. For all cities, urban and rural air temperatures are found to increase strongly, up to 7 °C. However, the urban heat island intensity in most cases increases only slightly, often even below the range of uncertainty. A potential explanation, focusing on the role of increased incoming longwave radiation, is put forth. Finally, an alternative method for generating urban climate projections is proposed, combining the ensemble temperature change statistics and the results of the present-day urban climate.
Highlights
There is increasing concern regarding the impact of global climate change on cities
Cities tend to be warmer than their rural surroundings, a phenomenon called the urban heat island (UHI), exposing urban residents to much higher levels of heat stress than people living in the nearby rural areas
The goal of this study is to couple UrbClim to as large as possible an ensemble of global climate models (GCMs) contained in the Coupled Model Intercomparison Project 5 (CMIP5) archive of the Intergovernmental Panel on Climate Change (IPCC) and conducting simulations for present (1986–2005) and future (2081–2100) climate conditions, considering the Representative Concentration Pathway (RCP) 8.5 scenario, to assess the evolution of the UHI for a number of cities all over the world
Summary
There is increasing concern regarding the impact of global climate change on cities. Together with drought and flooding, extreme heat stress is perceived as a problem that may increase considerably if no action is taken. Global climate models (GCMs) predict an overall increase in air temperature and, consistently, a rise of the number, frequency and intensity of heat waves [1,2]. Cities tend to be warmer than their rural surroundings, a phenomenon called the urban heat island (UHI), exposing urban residents to much higher levels of heat stress than people living in the nearby rural areas. Cities experience higher air temperatures than their rural surroundings, with night-time temperature differences up to 10 °C under favorable conditions [4]. Considering that cities are home to the majority of humans and given that cities are vulnerable because of the concentration of infrastructure and economic activity, this is all the more relevant
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