Comment: Tackling the growing problem of urban heat

Will Cavendish, Global Digital Services Leader at Arup, explains how digital tools can equip us to deal with the threat of rising city temperatures.

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This year is on track to being the hottest on record. The UK saw its hottest June, China logged a temperature of 52.2°C, and Canada saw record wildfires raging, displacing thousands. And we know the problem is getting worse, with certain groups including people from lower-income communities, those with pre-existing health conditions, older adults and infants feeling the impact of rising city temperatures most acutely.

Tackling the problem can’t be left to city leaders or even Chief Heat Officers alone. The built environment industry has a major role to play – we need to better understand how our current designs are exacerbating rising urban temperatures, and how we can design better in the future.  AI and digital tools are at the heart of enabling us to do this.

That’s why we launched our Urban Heat Snapshot – to help city leaders, urban designers and planners better understand how heat affects different parts of a city, and suggest the impactful actions they can take to mitigate extreme effects.

In our study, we used rapid, complex modelling to map the most extreme “hot spots” in six major cities around the world to give more insight into how heat was impacting these cities, and the role of the built environment in this.

Traditionally, complex heat modelling has been the preserve of academia and been a time-consuming exercise. Outside the universities, measuring and understanding urban heat has often been crude, with people sent out into the field to measure with thermometers, or land surface temperatures taken which don’t really give a sense of how people experience heat on the ground.

We worked closely with University of Reading in the UK to develop our UHeat tool, combining remote sensing data with an advanced climate model to calculate urban heat island (UHI) effects across an entire city. UHeat gives those shaping the built environment a tool that lets them test different scenarios and interventions and give evidence to support different solutions. And it demonstrates how advanced digital tools can bring academic models to real-word scenarios to find the causes of the UHI effect.

With this tool, we were able to rapidly understand with great precision where extreme “hot spots” were located. In the majority of cities, we found the hottest spots had less than 6 per cent vegetation cover, while the coolest spots in most cities had over 70 per cent and were found almost entirely in parks, away from residential and commercial areas. This contributed to massive temperature swings within cities, with Madrid’s built up downtown experiencing heat almost 8°C hotter than El Retiro Park a short distance away.

And within Madrid, severe hot spots meant 500,000 children and elderly people living with evening UHI heat spikes of 7°C or more. In London’s urban centre, almost a quarter of a million elderly people and children saw heat spikes of 4°C compared to rural surroundings.

This information, overlayed with social data is hugely powerful in the hands of those shaping the built environment and helping cities build resilience in the face of climate change.

To give you one example, in Tanzania’s largest city, Dar es Salaam, UHeat has been used to evaluate its future urban heat profile based on projected increases in population. This has helped show the potential of nature-based solutions to tackle the UHI effect, reducing temperatures across the city as the number of habitants and scale of infrastructure increase.

Our industry must now use these digital tools – such as machine learning, satellite data, digital visualisations and advanced algorithms - to provide insights that can improve traditional engineering and urban design disciplines – to create targeted solutions and fresh approaches.

As we approach COP28, where leaders will need to address the insufficient progress we are currently making in both tackling and adapting to climate change, our industry has the opportunity to show the huge contribution we can make. Digital tools are a game changer when it comes to understanding and building cities’ preparedness and resilience to rising heat – now is the time to harness them.