Urban Overheating and Cooling Potential in Australia: An Evidence-Based Review

Abstract

Cities in Australia are experiencing unprecedented levels of urban overheating, which has caused a significant impact on the country’s socioeconomic environment. This article provides a comprehensive review on urban overheating, its impact on health, energy, economy, and the heat mitigation potential of a series of strategies in Australia. Existing studies show that the average urban heat island (UHI) intensity ranges from 1.0 °C to 13.0 °C. The magnitude of urban overheating phenomenon in Australia is determined by a combination of UHI effects and dualistic atmospheric circulation systems (cool sea breeze and hot desert winds). The strong relation between multiple characteristics contribute to dramatic fluctuations and high spatiotemporal variabilities in urban overheating. In addition, urban overheating contributes to serious impacts on human health, energy costs, thermal comfort, labour productivity, and social behaviour. Evidence suggest that cool materials, green roofs, vertical gardens, urban greenery, and water-based technologies can significantly alleviate the UHI effect, cool the ambient air, and create thermally balanced cities. Urban greenery, especially trees, has a high potential for mitigation. Trees and hedges can reduce the average maximum UHI by 1.0 °C. The average maximum mitigation performance values of green roofs and green walls are 0.2 °C and 0.1 °C, respectively. Reflective roofs and pavements can reduce the average maximum UHI by 0.3 °C. In dry areas, water has a high cooling potential. The average maximum cooling potential using only one technology is 0.4 °C. When two or more technologies are used at the same time, the average maximum UHI drop is 1.5 °C. The mitigation strategies identified in this article can help the governments and other stakeholders manage urban heating in the natural and built environment, and save health, energy, and economic costs.

Lowering the Temperature to Increase Heat Equity: A Multi-Scale Evaluation of Nature-Based Solutions in Toronto, Ontario, Canada

“…This is consistent with the findings of previous studies. For example, urban trees tend to be more effective in reducing outdoor air temperatures than other types of vertical and horizontal greenery [100][101][102][103]. However, a combination of various types of green infrastructure, such as green roofs and green walls, requires less space and also has the potential to increase the overall efficacy of beneficial impacts [46,64,[103][104][105][106].…”

The Effect of the Substrate on the Optic Performance of Retro-Reflective Coatings: An In-Lab Investigation

“…UHI could also be worsened by the ongoing climate change, which is responsible for increasingly extreme events occurrence, more frequent heatwaves, and urban overheating [4][5][6]. In Yenneti et al (2020) [7], a collection of studies on UHI intensity in 10 different Australian cities is reported, showing that the UHI magnitude ranges between 1 and 13 • C in the investigated sites.…”

“…These facts lead to a further overheating, contributing also to the depletion of the urban environment and outdoor thermal comfort [7].…”

A New Approach to Studying Traditional Roof Behaviour in a Changing Climate—A Case Study from the Mediterranean Island of Malta

“…Most of the baseline methods used here are applicable to all roof types, and these include in-situ air and surface temperature measurements, and numerical and experimental studies [34], whilst others are specific to the roof type such as CRHT modelling (Cool Roof Heat Transfer) [35], hydrological modelling of hypothetical roof greening scenarios using EPA SWMM [36], coupled hygrothermal transfer models [25] for green roofs or, in the case of evaporative roofs, specific experimental set-ups to measure thermal changes instantaneously and under the same environmental conditions for a variety of porous media, to determine optimal material characteristics [37]. Some methodologies work well for two types of roofs where similar cooling mechanisms occur, such as simulations using the Penman model [38] for both green roofs and evaporative roofs or the 'Weather Research and Forecasting Model' used to measure the benefits and efficiency of green and cool roofs [38].…”