Updated: Jun 14
Urban microclimates are burning up and millions are at risk.
The urban heat island effect or UHI is a phenomenon which causes heat accumulation within urban areas. These heat islands occur when urban spaces replace the land cover with surfaces that are heat absorbents like pavements or buildings. This change in the surfaces means that there is lesser evaporation and absorption of moisture, which means a lack of cooling mechanisms. This phenomenon leads to these areas being hotter compared to their rural equivalents.
(Also read: How Urban Green Spaces Can Lead To Gentrification)
Causes of Urban Heat Island Effect
Overbuilding and Waste Heat Generation
Probably the number one cause for the formation of heat islands is the construction of pavements and buildings which make sure that the water runoff is not absorbed and evaporated. These cycles of absorption and evaporation are essential for cooling down areas. Darker-coloured buildings trap heat while taller buildings slow down wind velocity resulting in slower convection cycles.
These buildings are also air-conditioned, which dispenses heat directly into the surrounding air, further adding to the problem.
Source: The Deutscher Wetterdienst
Lack of vegetation
Another cause is the lack of vegetation. Plants absorb carbon dioxide and cool the environment, the lesser the greenery the greater the temperature. Other than aiding the cycle of evapotranspiration, these green spaces are crucial in providing shade and preventing erosion. Both lack shade and erosion come with their own set of repercussions that need to be dealt with.
The pollution caused by factories and vehicles traps solar radiation, preventing heat from dissipating, and further making the problem worse.
These causes don’t exist in isolation but occur simultaneously and have an increasingly dangerous impact on the environment.
Effects on Climate & the Environment, Human and Economic Health
Just like most phenomena, UHI is also multifaceted when it comes to its effects, and it is not a compliment. The more the different arenas of our existence get affected by UHI, the more worried we should be. It means that the days that we do not do something to fix this mammoth problem we’ve created, are the days we are taking away from our future generations. The effects are not just climatic and environmental but also take a toll on human and economic health.
The high temperature of pavements heats the rainwater runoff which drains into water bodies and heats them up. This affects the metabolism and reproduction of aquatic life, and can even be fatal.
Urban heat islands create a local low-pressure area, where cool air from the adjacent area converges to create clouds and leads to unseasonal rains which can have immense negative impacts on the crops and in the long run, on the orientation of seasons as we know them.
UHI, if allowed to persist, will cause not just general discomfort to humans but also increase the risks of heat-induced strokes, debilitating exhaustion, cramps and respiratory diseases.
It is not a foreign concept that uncomfortable working conditions equate to less productivity, but this also means that in order to create pleasant working conditions the costs of cooling these overheated buildings will rise which will in turn degrade the quality of air. This forms a vicious cycle where one cause feeds one effect which feeds another cause and it becomes never-ending.
But, what are the solutions?
The most common solution seems to be, greater vegetation cover and green roofing, where the roofs of the tall buildings are covered in grass and plants in order to keep them cooler by absorbing the heat. This also ensures improved air quality and keeps cooling costs in control. Another solution can be light-coloured buildings, these are reflective and cooling. These solutions do not realise their full potential until they’re backed by statistics and systematic entities. With the governing and organisational bodies laying down proper systems to award helpful and penalise harmful activities, these practices can be controlled.
In a worldwide culture of bigger and taller buildings, factories, and carefully constructed structures, being a sign of economic and developmental prowess, introducing the notions of over-industrialization, over–urbanisation and over-building can be tough. There is a tradition of taking what is not ours to take that is passed down from generation to generation. This tradition carries the weight of the destruction we’ve done to the planet, and it’s the present generation’s responsibility to put an end to it.
(Also Read: What does becoming a C40 city mean for Mumbai?)
Reduce Urban Heat Island Effect, United Nations Environmental Protection Agency, 23 March 2022
Urban Heat Island, National Geographic Resource Library
Causes, Effects and Solutions To Urban Heat Island, Conserve Energy Future