Articles Asia Energy & Environment

Pakistan’s Urban Heat Islands

Image Credit: El-Balad
Pakistan’s Urban Heat Islands

The geography and climatic patterns of Pakistan encompass a great variation in seasons, mountain ranges, and plains. The climate of the country can be categorised as arid with overall hot summers or cold winters with varying humidity. However, the sustained high temperature and humidity, due to increasing climate change, have long been recognised as a significant weather hazard.

The high heat indexes are evidence of a climate crisis in the country. This rising heat index occurs as a result of urban heat island (UHI), a phenomenon in which a metropolitan area has a higher temperature than the surrounding less developed rural areas. The temperature difference between the rural and urban areas depends upon “how well the surfaces in each environment absorb and hold heat”. Majorly the heat originated in urban areas is due to an increased amount of activity of people and by the use of automobiles which put out excessive energy in the environment. Moreover, the construction of industrial buildings close together, and the used materials are good at insulating, or holding in heat. This insulation makes the areas around buildings warmer.

Additionally, in an urban heat island, temperature can arise all year long, both day and at night. At night the temperatures remain high because the city infrastructure blocks heat coming from the ground, from rising into the cold night sky. Because the heat is trapped on lower levels, the temperature is warmer. Moreover, due to lack of vegetation, rain and ultimately no vaporization, the cities become predominantly virtual urban deserts, resultantly causing increased level of heat. The urban heat island effect is more noticeable during the summer and winter seasons. This urban heat island could be one of the major reasons for recurrent heat waves in places where there is a highly variable summer season. The extreme heatwave is not simply a day with high maximum temperature, but it is a combined effect of temperature and humidity.

This rising heat index occurs as a result of urban heat island (UHI), a phenomenon in which a metropolitan area has a higher temperature than the surrounding less developed rural areas.

In Pakistan, according to the analysis of heat index, there has been an eminent increase in temperature for the past few decades. The major effect of UHI is associated with heatwaves. The extreme weather begins from May and extends up to September.
In 2015, an intense heatwave struck the country, causing a large number of causalities, especially in Karachi with the record temperature ranging from 42 – 45°C. In southern Punjab, 40°C was recorded in Multan, whereas several areas of the Balochistan province were also affected, where temperature touched 49°C in Sibi and Turbat.
Thus, it shows that the areas of the country affected by a heatwave with maximum temperatures – greater than 45°C – extended over most parts of southern Punjab, and northern and western Sindh including Karachi. As a result of the severe heatwave, many deaths due to heatstroke were reported in Karachi, Hyderabad, Noshero-Feroz, Dadu, Badin, Thatta, and Tharparkar.

Since the city of Karachi is the business hub of Pakistan, there is a high price to be paid by the financial capital of the country. Due to the growing population and urbanisation, the city is witnessing the increasing effects of climate change. The city hosts a population of more than 18 million. Rapid urbanisation and global warming have inflicted the UHI effect on the city. Moreover, the weather conditions due to which such extreme calamities take place are caused by persistent air depression upon the Arabian Sea.

In addition to the causes of urban heat islands, in Karachi specifically, the UHI effect is rising due to the slowed process of evapotranspiration. Moreover, in the past years, the increase in the number of buildings has resulted in the urban canyon effect. This resultant effect refers to the provision of multiple surfaces for the reflection and absorption of sunlight, ultimately increasing the city’s temperatures. Additionally, the effect of the increased number of skyscrapers leads to blockage of wind, which also inhibits cooling by convection and airborne contaminants from dissipating. It results in higher levels of pollution, drifting the local wind patterns and humidity.
The UHI causes severe damage to sectors from industries, health, and commerce, to agriculture, infrastructure, and education. Communities across the city have to face the consequences due to the UHI effect. Likewise, the increasing energy demand, air conditioning costs, resultant greenhouse gas emissions, heat-related illnesses, lower water quality, and food insecurity adversely affect the people.

This effect of increasing climate change, not only causes stress for the outdoor workers but animals as well. Moreover, the decrease in agricultural production, increased demand for clean water supply, and shifts in tourism preferences due to higher temperatures have amplified the risks regarding sporting and outdoor recreational activities.

With an increase in urbanisation, the UHI effect is bound to increase.

As a result of higher energy demands in summer, UHIs are often subject to “rolling blackouts”, or power outages. “Utility companies start rolling blackouts when they do not have enough energy to meet their customers’ demands”. But efforts are continuously made to reduce these dire effects by the planting of “urban forests” in Lahore and Karachi by a Pakistani environmentalist. Such micro­-parks will help a city breathe and will assure natural recovery from the UHI effect. The future hope is to see such forests in smaller cities like the hottest city of Pakistan, Jacobabad, “where government officials will see the benefit of growing urban forests overbuilding”.

Another plan propagated by the government was the use of Geographic Information System (GIS) mapping to identify city hotspots, to set up first response centers (FRCs) in Karachi. Moreover, these FRCs were planned to “provide immediate first aid treatment to vulnerable residents at their doorstep before sending critical patients to tertiary care response centers”. For on the ground implementation of the plan, volunteers were arranged who would be mobilised as soon as their support was needed.

In the view of scientists, to reduce the deadly effects of climate change, city dwellers, architects, and designers all have to work to reduce people’s impact on urban areas. Planting more trees and specifically using green roofs, aid in keeping the temperature low. Plants not only absorb carbon dioxide but also reduce the heat of the surrounding areas. Lighter coloured materials on buildings should be used as they reflect more sunlight and trap less heat. In developed countries, architectural methods are being tested to reduce UHI. By “shaping the buildings and wind towers, which are big, clever tubes that capture wind up above the roofline of the city and push it down to street level”. Furthermore, different technologically advanced techniques are being used to map the city temperatures using satellites and instruments at ground level.

With an increase in urbanisation, the UHI effect is bound to increase. This will become a hindrance in the path of carrying out daily activities during the summer season. “Heatwaves are bound to occur more frequently and it is important to be well equipped to deal with them”.

Rida Anwar

Rida Anwar is a Research Assistant at the Centre for Strategic and Contemporary Research. She has studied International Relations from the National Defence University, Islamabad.

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