Arup's Uheat reveals Melbourne and Brisbane’s most extreme ‘hot spots’

The findings show that Melbourne Central and Brisbane’s Queen Street are up to 6°C hotter than they would be in an undeveloped setting. 

UHeat draws on an advanced climate model by the University of Reading in the UK and demonstrates how advanced digital tools can bring academic models to real-word scenarios to find the causes of the UHI effect. It can then rapidly model solutions to show how the strategic deployment of nature and other interventions can help cities reduce the impact of hot spots. The tool has already analysed a diverse range of cities: Singapore, Cairo, London, Los Angeles, Madrid, Mumbai and New York.

In the majority of cities, the hottest spots had less than 6% vegetation cover, while the coolest spots in most cities had over 70% and were found almost entirely in parks. Melbourne and Brisbane results were in line with these findings, showing leafy parklands with large percentages of permeable surface areas as least affected by the urban heat island effect.

Arup’s Global Resilience and Adaptation Lead Dr Kaitlin Shilling hopes urban planners and designers will take up the tool to mitigate the urban heat effect and improve the lived experience of for the millions of Australians living in major cities.

“If we keep resilience front of mind in the design process, we can create neighbourhoods that are cool, both in terms of temperature and urban amenity. We need to think beyond just green spaces and trees to keep temperatures down, and consider how to capture breezes, increase shade and incorporate materials that are cooler. The benefits of these designs expand beyond minimising heat – they can improve the vibrancy of urban streets, enhance health and wellbeing by encouraging walkability, and also have secondary resilience benefits by acting as flood mitigations.” said Dr Shilling.

Cities are getting hotter due to climate change, with the number of cities exposed to extreme temperatures, 35°C and above, expected to triple by 2050.*  In Australia, major heatwaves have caused more deaths since 1890 than bushfires, cyclones, earthquakes, floods and severe storms combined. Also, it is increasingly understood that around the world, less socio-economically advantaged neighbourhoods are more at risk to heat exposure, due to factors such as a lack of trees and a lack of air conditioning. **

Arup’s Urban Heat Snapshot is one of the few international comparisons of the UHI effect on air temperatures during both day and night-time. This method is much closer to people’s actual experience than cruder satellite analysis of land surface temperatures, which can be skewed by the dramatic highs of heat-absorbing materials on roofs and roads.

Arup Cities Leader, Australasia, Malcolm Smith, stressed the importance of designing for cool as Australian cities grapple with growing populations and a national housing crisis.

“Designing cities that are sustainable, inclusive, and equitable means addressing key issues that impact on the health and wellbeing of the people that live, work, and play in these spaces. Planning and development processes urgently need to need to prioritise and emphasise environmental efficiencies, such as insulation, and wind corridors,” said Mr Smith.

He added, “I’m a big fan of improving tree canopies. Trees planted decades ago can grow into iconic markers for neighbourhoods. But a mature tree canopy takes years to grow. We know that 80-90% of the cities that will exist in 10 years is made up of what we’ve already built, so mitigation and retrofits have to be part of the equation.”

References

* Around 200 million city-dwellers in over 350 cities live with summer temperature highs of over 35 degrees Celsius. The number of cities exposed to extreme temperatures will triple by 2050. C40 Cities – Heat Extremes 

** A study by Yale School of Forestry and Environmental Studies (T Chakraborty) of 25 cities around the world found that in most (72%) of cases, poorer neighbourhoods experience elevated heat exposure due to factors such as lower vegetation density.

*** Study published by The Lancet: Cooling cities through urban green infrastructure: a health impact assessment of European cities