Impact of global climate change and urbanization on megacities
Do Ngoc Khanh (a, b*), Alvin C. G. Varquez (b), Manabu Kanda (b)

a) SIT Research Laboratories, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo, Japan 135-8548
b) Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan 152-8550

Abstract

Global climate change and urbanization-induced warming (urban heat island effect) are the two main drivers of warming in cities. In the projection of future climate, coarse-resolution global climate models are not suitable for looking into the heterogeneous urban surface and their changes. On the other hand, regional climate models, which are capable of looking into cities in detail, have never been used to investigate the global urban climate. Here we show that urbanization significantly increases exposure to extreme warming for megacity residents. We reflect urbanization between the 2010s and the 2050s into our model by considering the spatiotemporal change in urban surface (buildings and anthropogenic heat emissions) induced by urban population and economic growth. We found that in the 2050s, under the worst-case scenario, 78 percent of megacity residents will be exposed to 2.5 K warming, much higher than the projection of 65 percent when urban warming is left out. Our results highlight the importance of accounting for local urbanization in future global urban climate projection. We also introduce the modeling framework used in this study. The framework is applicable for all cities worldwide and was incorporated into the Weather Research and Forecasting (WRF) model v4.6.

Keywords: global climate change, urban climate, WRF modeling, anthropogenic heat

Topic: Atmospheric Sciences