Over the last few years, once-in-a-generation events have been aplenty. We’ve been witnesses to unprecedented rainfalls, heatwaves, fires and many more calamities. Moreover, while such calamities have occured across various geographies, it is clear to see that our cities are the epicentres of climate impact. As a result, our cities coule become uninhabitable in the near future, and so we have a pressing need to re-think how our cities and communities are built.

In this article, we’ll look at why exactly our cities have become hotbeds for the ill-effects of climate change, and what we can do to mitigate 

The Urban Heat Island Effect

As a result of human activity, cities often become areas where temperatures are drastically different from their surrounding areas. The reason behind this occurrence is scientifically proven to be human activity – more specifically, from modification of land surfaces. A study in the Journal of Geophysical Research found that waste heat generated by energy usage is a significant contributor to making human settlements into heat islands. This makes sense at a surface level – after all, hotter areas call for using greater energy to make it cooler, thus, increasing the level of emissions and exacerbating the situation. But, let’s observe the more practical aspects of how the Urban Heat Island effect occurs so we can find indicators of it around us.

Cities have become hotbeds for climate change

A major contributor to this energy usage is the fact that dark surfaces, which are exposed to radiation in many cities due to a lack of green cover, absorb much more radiation, causing roads and buildings to become much hotter, thus increasing the need for cooling and energy consumption. This occurs primarily because materials commonly used in urban areas for pavement and roofs, such as concrete and asphalt, have significantly different thermal properties and surface radiative properties than the surrounding rural areas. So naturally, the usage of these materials call for a higher usage of energy, which results in higher temperatures than surrounding rural areas, thus becoming a heat island. 

Urban Heat Islands are also formed by the “urban canyon effect”, which occurs when tall buildings in an urban area provide surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated. Tall buildings also block the flow of wind and prevents polluted air from escaping, both of which contribute to the Urban Heat Island effect.

A map of India illustrating the monthly variation in daytime Urban Heat Islands

Another major reason for cities becoming urban islands is a lack of evapotranspiration in urban areas. In essence, evapotranspiration is the process of water evaporating into the atmosphere from the soil surface, which happens via plants and vegitation, and water bodies. In other words, a reduced green cover in cities lead to lesser evaporation from the soil to the environment, thus making the entire region hotter than its surrounding areas.

The solution?

Given how most of the world’s major cities were built before the need for climate action was as pressing as it is today, the situation might seem beyond helping. It might seem that while we can assuage the creation of Urban Heat Islands in the cities fo the future, there’s not much that we can do with the cities of today. However, this is pretty far from the truth.

We certainly need to re-think how new buildings, and new cities, are created in the future, however, there are a host of ways in which we can make our existing cities more liveable. 

Primarily, these methods include using lesser dark materials in construction of buildings and infrastructure, and increasing the amount of well-watered vegetation. Many cities including Singapore and Los Angeles, have adopted strategies including white and green roofs, planting trees on roads and green parking lots to reduce reliance on artificial cooling and excess energy use.

A recent research paper published by A. H. Rosenfeld of University of California – Berkeley estimated that through the use of the techniques mentioned above, urban temperatures could be reduced by approximately 3 °C (5 °F). The model used in the publication considered an area of Los Angeles where $1 billion was spent to plant 10 million trees, re-roof 5 million homes and painting a quarter of the roads white. The model predicted that taking those measures would cause an estimated $170 Million in savings from reduced air-conditioning expenses and $360 Million in savings by mitigating smog related health savings.

Closing thoughts

Clearly, the ill-effects of climate change are starting to affect human populations in a real way. However, despite the fact that the situation seems dire, we believe it makes sense to re-think our cities from both a financial and health standpoint. That’s why, aside from advocating for methods to mitigate Urban Heat Islands, we have created a revolutionary carbon negative building material – Agrocrete – which can help the world build better buildings. We believe that while it is certainly possible to be carbon-neutral by 2050 and begin reversing climate change, the time to act is now.