In the fifth and final COP26-themed blog curated by the Climate Justice and Social Policy Group, Dr Komali Yenneti, Lecturer in Geography, Urban Planning and Environment at the University of Wolverhampton, provides a perspective from Australia on what climate smart and just cities and communities could look like in the not so distant future.
Australia is in the midst of a ‘smart cities’ revolution. The vision for a Smart Cities Plan promises to improve the liveability, productivity and sustainability of cities and towns across Australia. But can this objective be achieved when Australian cities are facing a complex set of challenges related to climate change, and when the smart cities mission tends to focus on ‘hard’ digital technologies? Average urban temperatures in the last decade are possibly the highest in at least the past century. Even without the planet warming, cities already face a problem – the Urban Heat Island (UHI) effect, a phenomenon caused by urban sprawl, intensive roads and pavements, dark building surfaces, and reduced green cover. Research suggests that the magnitude of the UHI effect in Australian cities is significantly increasing: the current average maximum intensity is 1-7°C compared to 0.5-3°C in the early 1990s.
The UHI effect is more severe in Australia, with increasing episodes of extreme heat events causing a serious impact on public life and the economy. Historically, heat waves have killed more people in Australia than any other extreme weather events, with 2% of all deaths related to heat. The risk of mortality across Australian cities rises by an average of 10-15% when the ambient temperatures exceed 30°C. Urban heat has a significant impact on energy and the economy, with research suggesting that demand for cooling will increase by 0.45-4.6% per degree increase of ambient temperature, and that labour productivity will decline by at least 20% by 2050 as average temperatures rise.
To counterbalance high urban temperatures and their impacts on people and places, appropriate climate-smart technologies and strategies can be used by policymakers and urban planners. These innovative solutions can be broadly categorised into two areas: 1) solutions that decrease the absorption of solar radiation and release of heat to the atmosphere and keep urban surfaces cool (e.g. through cool roofs and cool pavements), and 2) increase evapotranspiration in urban environments (e.g. through urban greenery, green infrastructure and water-based systems).
Water-based urban landscapes
The use of water for cooling has been known for many centuries. Water-based urban landscapes, such as lakes, rivers, and wetlands contribute to ‘urban cooling islands’, and can decrease urban ambient temperatures by 1-2⁰C. Apart from natural water bodies, a variety of active, passive or hybrid water systems like pools, ponds, fountains, evaporative wind towers, sprinklers and water fountains can also be implemented in public spaces for both decorative and climatic purposes.
Various forms of natural and designed urban greenery, such as urban parks, street trees and hedges, and open spaces decrease urban temperatures and cool the surrounding air through shading, evapotranspiration, and the alteration of wind movement. Urban greenery may for a part of urban landscapes and may also be integrated into the building envelope through green roofs and green walls.
In tropical and subtropical climate zones with sunny summer skies, like Australia, urban greenery is an effective and economical heat mitigation strategy. For example, increasing street tree and canopy cover by 40% can lower ambient temperatures by as much as 1-2.5⁰C in cities such as Melbourne. The results of a study in Adelaide also demonstrated that green roofs can not only reduce daytime temperature in summer, but also reduce energy loads for cooling. However, to design urban green spaces with the greatest cooling effect in hot summer weather, architects and urban planners need to collaborate in design interventions.
High reflective materials – also called cool materials – can greatly mitigate the UHI effect and extreme temperatures, increase thermal comfort, and reduce energy demand in air-conditioned buildings. Advanced cool materials for buildings (e.g. cool roofs and cool facades) and street surfaces (e.g. cool roads and cool pavements) with very high reflectivity and emissivity are now commercially available. Examples include white paints, elastomeric coatings, reflective synthetic binders and EPDM (Ethylene Propylenediene Tetrolymer Membrane). More recent advances have been made in water retentive or permeable materials, heat reflecting coatings, colour changing coatings, and photovoltaic based pavements, which can also support aesthetics. Cool materials can mitigate maximum summer indoor temperature up to 2°C and contribute to cooling load reductions in the range of 10-40% in moderately insulated buildings.
Combining mitigation strategies
The urban heat mitigation potential from the combined use of different technologies and systems (e.g. greenery and reflective materials) is higher than the contributions of each individual technology. Individually, each strategy can mitigate high urban temperatures (up to 1.89°C), but taken together, in combination, and/or with citywide adoption, they can significantly reduce the UHI effect itself while also providing additional co-benefits.
Urban heat management has been an important policy agenda in Australia, although largely as part of national government efforts on disasters, sustainable development, and global climate change. Some local governments have developed some regulations (e.g. the dark roof ban in Sydney), demonstration projects (e.g. the cool pavement trial in Sydney), incentives (e.g. green roofs/walls/facades in Melbourne), planning instruments (e.g., Penrith’s Cooling the City strategy) and public awareness activities (e.g., Cool Your Roof in Townsville). However, these initiatives are ad-hoc and fail to address urban heat in a comprehensive way. Most urban heat mitigation policies and strategies are voluntary and face competing challenges from other sectors, such as urban development, energy and housing. In addition, the issue of urban heat is not considered important for the health and wellbeing of communities.
It is now more important than ever that cities respond to urban heat, as more than 90% of Australians live in urban areas. The exclusion of urban heat issues in policy and the planning of smart cities, and more recently in ‘net zero’ plans, is a gross climate injustice. Relevant policies that bring together communities, industry and governments are crucial for the implementation of disruptive climate-smart technologies and strategies and for their integration into mainstream smart cities, net zero, and urban policies. The importance of partnerships cannot be understated, as we recognise that the process of delivering ‘climate smart cities’ is 1) embedded in and supported by multi-stakeholder and multi-scalar governance structures, 2) processual in nature, and 3) multi-faceted, activated through combinations of technologies, adaptive actions, local and indigenous knowledge, and grassroots innovation.
Dr Komali Yenneti is a Lecturer in Geography, Urban Planning and Environment at the School of Architecture and Built Environment, Faculty of Science and Engineering, University of Wolverhampton. She is also an Honorary Fellow at the Australia-India Institute, and is the founding Chair of the International Geographical Union’s Young and Early-Career Geographers Task Force (IGU-YECG).
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