Cities start to feel the heat from climate change

UHIs present enormous challenges for humans, says Henry Ibitolu, Ph.D student in Future Cities Engineering at the Universities of Edinburgh and Glasgow. His research focuses on mitigating UHI effects by making cities of the future more sustainable and energy-efficient.

“First, urbanisation means natural surfaces are converted into built-up structures that alter the thermal dynamics of the immediate environment. Second, urbanisation is often accompanied by densification. This increases the number of occupants of structures without increasing their footprint. This is seen in expanding cities, where suburban dwellings are often replaced with duplex houses or low-rise apartment blocks to meet housing demand.”

So, how can we turn down the temperature? Most cities are already built-up, meaning we can’t radically alter the urban geometry, continues Ibitolu. Plus, there is limited space to add more greenery. There are solutions, however. These include using lighter-coloured materials and reflective coatings to reflect more sunlight and absorb less heat. White-washing black asphalt or roofs can help.

We can also look to the past to find suitable solutions for the future, adds Ibitolu. “For centuries, ancient architects and builders have relied on the thermal efficiency of earth materials (earthen bricks and rammed earth) for building. These earth materials have significant thermal properties and present a low-embodied carbon alternative to conventional cement construction.”

Ibitolu explains that his research investigates the extent to which cement building materials can be replaced with thermally massive earthen materials. “By doing so, we can mitigate emerging UHI effects and alleviate the need for energy-intensive air conditioning.”

Adding external facades can improve indoor thermal and energy efficiency. Using green roofs, namely roofs of buildings covered in plants, and increasing the amount of greenery around a city or simply adding more trees for shade helps absorb carbon dioxide, a leading pollutant, and lower temperatures. We all know the temperature difference between a tree-shaded park during the summer months compared with an exposed, sun-baked car park.

Varying the differences in building heights can also create more air circulation, which has a cooling effect.

In other words, with the right degree of urban planning and the right amount of investment and effort by architects and the real estate industry, we can mitigate urban warming.

Essentially, in future, architects, city designers and urban planners need to construct buildings with energy performance in mind, continues Ibitolu. “They should also consider how their performance will influence structures around them and the nearby urban microclimate. The outcome is to contribute towards achieving the UN sustainable goals and to ensure a sustainable city for all.”

The COP26 UN Climate Conference has kept the Paris Agreement targets alive, gathering commitment to cut emissions to stay within the global warming limit of 1.5°C. Achieving a threshold of 1.5°C could avoid between 110 and 2,720 annual heat-related deaths per US city over the next 30 years, according to research by Eunice Lo, a climate scientist at the University of Bristol.

By planning more efficient infrastructure and investing in future-proof buildings, cities can limit the worst effects of dangerous heat increases, lower their carbon footprint and adapt to a warming world. The solutions are there. It’s simply up to us to use them.