The impact of climate change and urban growth on urban climate and heat stress in a subtropical city

Abstract

Urban residents face increasing risk of heat stress due to the combined impact of climate change and intensification of the urban heat island (UHI) associated with urban growth. Considering the combined effect of urban growth and climate change is vital to understanding how temperatures in urban areas will change in the future. This study investigated the impact of urban growth and climate change on the UHI and heat stress in a subtropical city (Brisbane, Australia) in the present day (1991–2000) and medium term (2041–2050; RCP8.5) during summer. A control and urban growth scenario was used to compare the temperature increase from climate change alone with the temperature increase from climate change and urban growth. Average and minimum temperatures increased more with climate change and urban growth combined than with climate change alone, indicating that if urban growth is ignored, future urban temperatures could be underestimated. Under climate change alone, rural temperatures increased more than urban temperatures, decreasing the effect of the UHI by 0.4 °C at night and increasing the urban cool island by 0.8 °C during the day. With climate change, the number of hot days and nights doubled in urban and rural areas in 2041–2050 as compared to 1991–2000. The number of hot nights was higher in urban areas and with urban growth. Dangerous heat stress, defined as apparent temperature above 40 °C, increased with climate change and occurred on average 1–2 days every summer during 2041–2050, even in shaded conditions. There was higher temperature increases with urban growth and climate change than with climate change alone, indicating that reducing the effect of the UHI is vital to ensuring urban growth does not increase the heat stress risks that urban residents will face in the future.

Urban Climates and Climate Change

“…On the evolution of UHI in a changing climate, studies show quite systematically that the phenomenon does not intensify. Nighttime UHIs remain stable or decrease slightly (164,172,173,174). The first global simulations including cities (175) have shown the generalization of this trend.…”

Climate change impacts on heat stress in Brazil—Past, present, and future implications for occupational heat exposure

“…(2019) and Chapman et al . (2019) pointed out that urbanization and climate change will pose serious health risks to people living in large cities due to extreme heat.…”

“…Kikumoto et al (2016) and Suzuki-Parker and Kusaka (2016), using future projections, showed that in Japan increased heat may impact the urban thermal environment with a significant reduction in safe labour hours. In studies conducted in China and Australia, Wang et al (2019) and Chapman et al (2019) pointed out that urbanization and climate change will pose serious health risks to people living in large cities due to extreme heat.…”

The Effects of Extreme Heat Adaptation Strategies under Different Climate Change Mitigation Scenarios in Seoul, Korea

“…Many studies have assumed that cities will endure increased extreme heat events (including heat waves) in the future [12][13][14]. For instance, eastern Mediterranean cities, such as Athens and Florina have been projected to experience further lengthening of extreme hot seasons compared to the increase from 1971 to 2000 by approximately one month in 2021-2050, and two months in 2071-2100 [14].…”

“…Pakistan is also expected to face more severe impacts from climate extremes, especially a large increase in the frequencies and magnitudes of extreme heat [12]. In the subtropical areas of Brisbane, Australia, dangerous heat stress will occur on a minimum of 1-2 days per year during 2041-2050 [13]. In addition, cities in Korea are vulnerable to the frequency, magnitude and duration of hot events [15], which will cause a 5-7.2 times the number of deaths in the 2050s than before [16].…”