Combined impact of climate change and urban heat island on building energy use in three megacities in China

While global climate change (GCC) and urban heat island (UHI) effects have been extensively studied separately, their combined impact on urban microclimates remains poorly understood. This study introduces a novel lightweight simulation procedure that effectively integrates these two phenomena to assess their combined impact on urban microclimates in three representative Chinese megacities. By validating the selected global climate model (GCM) using observed weather data from the last decade, we demonstrate that incorporating UHI effects into future urban weather condition downscaling significantly improves prediction accuracy for local air temperature, reducing MRMSE by 0.56 degrees C, 0.34 degrees C, and 0.11 degrees C (17.09 %, 15.15 %, and 4.30 %) in Beijing, Shenzhen, and Shanghai. Moreover, simulation of prototypical building models in urban areas based on future representative year (FRY) weather data reveals that the changes in future cooling energy consumption range from -3.26 % to 100.24 % compared to cooling energy consumption under TMY with most positive change ratios. The trend of heating energy consumption can vary in cities from -98.68 % to 15.78 %. This integrated approach advances the understanding of combined impacts of climate change and heat island on urban environments and provides a computationally efficient framework for future urban climate predictions.