Heat adaptation for a cooler future in hot cities


Climate change has been an important issue in politics and global governance during the past one decade. However, not everyone believes that the world is doomed because of climate, at least not to the catastrophic levels projected in the mainstream media.

This is because the models—which we depend on to forecast future temperatures—continue to be faulty. They lack the ability to predict real-world temperatures, mostly forecasting unrealistic and exaggerated temperatures, as confirmed by recent scientific studies.

But there is a non-climatic warming factor that all people agree on: it is Urban Heat Island effect.

Urban Heat Island (UHI) is a phenomenon where built infrastructure such as buildings, roads, automobiles, and other artificial structures cause the urban centers to become more warmer than the surrounding non-urban areas that are usually devoid of such built infrastructures.

Heat-trapping materials such as Burnt Brick, Stone, Slate, Concrete are common construction materials in cities across the globe. These materials increase the internal air temperatures of rooms and spaces, especially when their roofs are exposed to sunlight.

UHI has been an increasingly common problem globally as many of the 21st century metropolitan cities are becoming denser with each passing year. The situation is worse in poor neighborhoods where houses are crammed and built with materials that increase thermal discomfort.

The UHI effect induced increase in heat does not merely cause discomfort to the residents in the city, but also causes a spike in energy used for air-conditioning and other electrical appliances. It is estimated that electricity demand in cities increases by 2–4% for each 1°C increase in temperature.

Multiple factors are known to exaggerate the impact of heat waves in cities. Observations in South Korea showed that heat waves tend to cause more mortality in city areas that were devoid of vegetation. In London, heat wave mortality was found to be particularly high among the elderly who lived in the outskirts.

Many cities, especially those in tropical countries, are getting warmer because of UHI and it is proving to be a real problem, threatening to increase heat-related morbidity and mortality.

It is necessary to have adaptive solutions that can reduce the impact of UHI effect on city dwellers and also prevent increase in energy demand. There are a number of innovative solutions that cities have been exploring and implementing in the recent years. Most of these methods help increase the thermal comfort for residents and commuters in the cities.

Cool-Roofs

Cool-roofing involves covering the roof of a building with an appropriate coat of paint or a simple sheet that reduces the induction of heat onto the roofs. Such a coating of paint or sheet usually have high thermal emissivity and solar reflective index, enabling them to reflect most of the heat and conduct less heat onto the roof.

Cool Roofs have been known to reduce indoor temperatures lower by 2 to 5°C on average. Studies in Jamaica have shown that internal ceiling surface temperature is reduced by an average of 6.8 °C and internal air temperature by 2.3 °C when cool paint coatings were used.

Cool-roofs are also affordable and can be utilized in slum areas where families cannot afford expensive cooling solutions like air-conditioners. Cool roofs could prove to be essential tool in enhancing the thermal comfort of the densely packed neighborhoods of cities that display a high vulnerability UHI effect.

Urban Greenery

Another innovative solution that is becoming popular is green infrastructure or urban greenery. The term encompasses a large number of solutions that involves increasing the green cover in urban areas.

Some cities like Seoul in South Korea have incorporated waterways and greenery in the middle of the city, by reclaiming lost waterways. Other like Singapore have implemented mandatory rooftop green infrastructure laws that requires the city’s buildings to have garden or green cover on their roofs.

European cities are beginning to implement green landscapes, including new urban parks to mitigate UHI. Other cities are increasing the tree cover in the urban areas. Though green facades–plants on vertical walls—are aesthetic in appearance, they may not be as effective as other solutions.

Cities can also implement airflow-sensitive construction guidelines where the buildings are constructed in a way which enhances air circulation and help lower the UHI effect. Cities can also build artificial water bodies as they are a well-known cooling source when accompanied by wind.

There is a likely a solution for every city. Depending on the geography, population density, climatic factors, and nature of existing built infrastructure, city authorities can devise customized urban cooling solutions that will help lower the thermal discomfort.

Instead of levying heavy carbon tax on businesses and spending billions to offset carbon dioxide emissions, cities and states can focus their efforts to fight real and existential climatic threats like UHI which have been sidelined because of the fanfare surrounding anthropogenic global warming.

  • "Vijay Jayaraj (M.Sc., Environmental Science, University of East Anglia, England), is an Environmental Researcher based in New Delhi, India. He served as a Graduate Research Assistant at the University of British Columbia, Canada and has worked in the fields of Conservation, Climate change and Energy."

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