Abstract
Climate change causing an increase of frequency and magnitude of heat waves has a huge impact on the urban population worldwide. In Indonesia, the Southeast Asian country in the tropical climate zone, the increasing heat wave duration due to climate change will be also magnified by projected rapid urbanization. Therefore, not only climate change mitigation measures but also adaptation solutions to more frequent extreme weather events are necessary. Adaptation is essential at local levels. The projected increase of the heat wave duration will trigger greater health-related risks. It will also drive higher energy demands, particularly in urban areas, for cooling. New smart solutions for growing urbanization for reducing urban heat island phenomenon are critical, but in order to identify them, analyzing the changing magnitude and spatial distribution of urban heat is essential. We projected the current and future spatial variability of heat stress index in three cities in Indonesia, namely, Medan, Surabaya, and Denpasar, under climate change and land-cover change scenarios, and quantified it with the Universal Thermal Climate Index (UTCI) for two periods, baseline (1981–2005) and future (2018–2042). Our results demonstrated that currently the higher level of the UTCI was identified in the urban centers of all three cities, indicating the contribution of urban heat island phenomenon to the higher UTCI. Under climate change scenarios, all three cities will experience increase of the heat, whereas applying the land-cover scenario demonstrated that in only Medan and Denpasar, the UTCI is likely to experience a higher increase by 3.1°C; however, in Surabaya, the UTCI will experience 0.84°C decrease in the period 2018–2042 due to urban greening. This study advanced the UTCI methodology by demonstrating its applicability for urban heat warning systems and for monitoring of the urban green cooling effect, as well as it provides a base for adaptation measures’ planning.
Highlights
Global mean temperature has increased by 0.87°C from the preindustrial period to the present day (Jia et al, 2019), and it is expected to continue to increase, in total 2.0–4.9°C by 2,100 (Raftery et al, 2017)
The urban areas we selected for this study are included in the National Action Plan on Climate Change Adaptation (RAN-API) of the Republic of Indonesia, which is a national effort aimed at designing adaptation strategies to climate change
The Universal Thermal Climate Index (UTCI)-based urban heat stress assessment performed in this study under climate change and land-cover change scenarios in three cities, namely, Medan, Surabaya, and Denpasar, included in the National Adaptation Plan of Indonesian government demonstrated that under future projections, Medan is the most vulnerable city in terms of increasing the UTCI level, followed by Denpasar and Surabaya
Summary
Global mean temperature has increased by 0.87°C from the preindustrial period to the present day (Jia et al, 2019), and it is expected to continue to increase, in total 2.0–4.9°C by 2,100 (Raftery et al, 2017). The temperature increase leads to more frequent and intense extreme heat events which cause adverse heat-related impacts that will result in human fatalities and economic damages. In terms of human health, urban areas are considered to be at higher risk due to the so-called urban heat island (UHI) effect, which means that urbanized areas tend to have a higher temperature than their rural surroundings (Loughnan et al, 2012). Since the global urban population is projected to increase by 68% by 2050 (UN DESA, 2019), the urgency of tackling the heatrelated risks in urban areas will become even a higher priority than at present
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