Heatwave Zoe became the first named heatwave this year. Spain are naming their heatwaves like we name cyclones, to raise awareness of how deadly extreme heat is and work towards reducing casualties. In the US, Heatwaves are the most lethal weather events, and they are getting more and more frequent.

Extreme heat is also a killer of economic activity for cities too, hurting small local businesses the most as people stay indoors to keep cool.

Across Australia we expect a big increase in heatwaves. In Adelaide it is projected that days over 35 degrees will go from historical averages of 18–25 days per year, up to 51–69 days per year by 2090. Western Sydney from 16 to 48 days per year.

Heatwaves are costing local communities millions already, and are only going to cost more in the future.

Scorching temperatures come at a hefty price for the community, with the City of Melbourne estimating an economic cost of around $1.8 billion. Heatwaves alone account for one-third of this impact. Delving into the specifics, the Urban Heat Island effect plays a significant role, contributing roughly $300 million to this economic toll.

What can local governments do to mitigate things? Strangely, one effective way is by how they manage their road network. How?

A Toxic Relationship

Roads make extreme heat worse.

Extreme heat makes roads worse.

Roads contribute about 33% to the urban heat island effect (UHIE) which makes our cities hotter than rural areas.

Rising temperatures are set to reduce the life of asphalt roads by 17%. This is due to an increase in environmental degradation of bitumen by increased temperatures and heatwave regularity.

Both of these have huge costs to local communities, both health and financial.

UHI related costs are forecast to be 10% of total Council spending in the future. That’s a multi billion dollar problem.

Maintaining roads is already under funded, to the tune of $10b each year - it’s only going to get worse with extreme heat.

What Can Councils Do?

Many projects around the world have demonstrated that local mitigation strategies are effective. One in Western Sydney recently demonstrated how vulnerability to heat varies from street to street and suburb to suburb. It concluded that it is at this level that operative actions against heat should take place.

At the community level, a cost-benefit analysis of UHI mitigation strategies for over 1,600 cities worldwide found that one dollar invested in cool roofs, along with a much smaller investment in green roofs and cool pavements, would return twelve dollars worth of benefits.

Estrada, F., Wouter Botzen, W. J., and Tol, R. S. J. A global economic assessment of city policies to reduce climate change impacts. Nature Clim Change 7, 403-406 (2017). https://doi.org/10.1038/ nclimate3301

Since improvements are more likely if convenient, easy and affordable (Bond et al., 2011), the key is to find cost-effective low-carbon retrofits and behaviour- change strategies to lower the effective temperatures felt by household occupants. These adaptation strategies may also mitigate climate change by lowering energy use and therefore carbon emissions.

What results can we expect?

Cooling roads:

•Reduces electricity costs. By reducing surface temperatures, electricity costs for households reduce by $150 per year.

•Reduces surface temperatures and can add 20% to the life of roads, worth $35,000 for every 1km length of a local street.

How much will adapting our environment cost?

Councils should first look at options that are substitutes for existing practices. This means no additional funding is needed, just different technologies that exist and are similar costs to currently used products.

Join in the conversation with SuperSealing and find out how some Australian Cities are already adapting for a cooler environment.