ue to extensive urban sprawl and aggressive removal of trees and other forms of vegetation, many cities have become unbearably hot. It is high time to reverse this trend by adopting local and international experiences proven to keep the cities cool.

Global climate change and the local realities of pollution, an increasing number of private vehicles, unsustainable urban growth developed in utter disregard of local climatic conditions, and the national electricity scenario of load-shedding and expensive tariffs have created serious challenges for human well-being, impacting health and productivity. Extensive use of air conditioning, too, is adding to the atmospheric heat.

Under the British Raj, the Garden City movement influenced Karachi’s urban planning. Farhan Anwar who teaches a social development and policy programme at Habib University, says its primary focus was to keep the city cool by harnessing and channelling the sea breeze. The urban plan involved designing 30-60 feet wide, straight avenues running east-west to allow the cool sea breeze to pass from the harbour and port area to the Old Town, the commercial districts around Bunder Road (MA Jinnah Road) and Frere Road ( Shahra-i-Liaquat) and into the residential areas around Elphinstone Street (Zaibunisa Street). The wind corridors, Anwar says played a crucial role in keeping Karachi cool and comfortable during summers.

Buildings were constructed with large windows and balconies facing southwest to maximise sea breeze capture. There were high ceilings and thick walls for insulation, verandas and porticos for shade, courtyards and internal gardens for cooling. Besides parks and gardens alongside canals, streams and fountains enhanced cooling through evaporation to improve airflow and provide recreational space. These design elements mitigated the heat and created a comfortable urban environment.

Over time, construction and development have changed the city’s urban landscape. Many of the wind corridors have been obstructed or altered, says Anwar. Coupled with global climatic changes that have raised the temperatures by 1.5 C, unplanned urbanisation in many cities, including Karachi, has made their downtowns excessively hot and humid.

Tall buildings and narrow streets trap heat, reduce wind speed and hold pollutants, creating a canyon effect. Such dense built-up areas in the downtown with asphalt roads and pavements absorb and retain heat, causing higher temperatures than the rest of the city. These factors interact with local conditions to exacerbate the canyon and urban heat island (UHI) effects. They keep the cities uncomfortably miserably hot during evenings.

Dr Sarfraz, the Sindh chief meteorologist, says that because of the urban sprawl and the UHI the night temperature in Karachi has risen by 1.4 C.

The average night temperature from 1960-1990 was 25.4 C. Between 1991 and 2020 it rose to 26.5 C.

The highest night-time temperature recorded in Karachi was 34.1° C. This was recorded on June 21, 2015, at the Pakistan Meteorological Department’s Karachi Airport weather station. Other notable nighttime temperature records in Karachi are, 33.5° C (92.3° F) on June 22, 2017, 33.2° C (91.6° F) on May 26, 2018, and 32.8° C (91° F) on June 1, 2020. Over the last fortnight, night temperatures in Karachi rose to 32 C.

Such high nighttime temperatures are often a result of UHI effect, heat waves and climate change.

According to Dr Sarfraz, since 1971 the number, duration, frequency and intensity of heat waves have increased.

Karachi’s urban sprawl has turned the city into a virtual furnace. The downtown is a maze of buildings that trap heat and humidity. By day, the sun beats down relentlessly, and by night, the concrete core retains the heat, offering little relief. The humidity is suffocating, making every breath feel like a hardship. The high population density, the limited green spaces, industrial activity, poor urban planning and inadequate waste management have made several towns of Districts East, Central, Korangi, South, Malir, and West vulnerable to heat stress.

Remedies

Modern urban planning solutions can help alleviate these effects by using ‘smart’ technologies, employing ‘mixed-use’ development, designing buildings with ‘passive’ solar techniques, designing ‘green’ buildings and retrofitting the existing ones. A critical factor is the incorporation of green spaces into the overall scheme of things.

Since greenhouse gases (GHGs) are the main cause of heating the planet, the new urban mobility (NUM) strategy aims to reduce vehicular emissions by having ‘mixed-use’ buildings, says Anwar. This modern approach integrates residential, commercial, recreational and industrial facilities in the same buildings, complexes or nearby blocks, he says. This brings together all the amenities like grocery stores, gyms, cafes and parks right. The cuts down lengthy commutes and allows for a reduced impact on the environment. Typical distances in such areas range from 0.1-0.5 miles for commercial and office spaces, equivalent to a 1-8 minute walk. The schools are typically 0.2-0.7 miles away, a 4-12 minute walk. Hospitals are 0.5-1.5 miles away, a 10-30 minute walk. The new urban mobility ensures that all transportation is by sustainable means like electric scooters and bikes, micro-transit shuttles and electric vehicles.

Singapore has employed artificial intelligence and big-data driven comprehensive smart transportation systems, including smart traffic management, or predictive traffic management to cut down on congestion. London has also introduced smart parking systems and bike-sharing schemes. Barcelona’s superblocks are pedestrian-friendly streets with reduced car traffic. The mobility-as-a-service (MaaS) platforms combine public transportation, car-sharing services and bike-sharing programmes into a single platform accessible to travellers via a digital app.

Green design

Anwar says, “They are revolutionising the way we design and construct our spaces, significantly reducing the carbon load.”They combine sustainable materials, energy-efficient systems and innovative technologies to minimise the ecological footprint. Solar panels, green roofs and rainwater harvesting systems enable them to harness natural resources, reducing reliance on fossil fuels and lowering greenhouse gas emissions. Additionally, smart building technologies optimise energy consumption, waste management and water use, further reducing the carbon load.

Several cities are designing buildings in a way that they do not require air conditioners or heaters irrespective of the external temperatures. Anwar says sophisticated technologies and building designs have mostly done away with ACs, fans and heaters in “passive buildings” significantly reducing carbon emissions. They maintain a consistent and comfortable internal temperature between 20-25° C (68-77° F) throughout the year, despite external temperatures ranging from -20° C to 40° C (-14° F to 104°F). The Passive House in Germany maintains an internal temperature of 22° C (72° F) in winter and 25° C (77° F) in summer, while the external temperature varies from -10° C to 30° C (-14° F to 86° F).

This is not limited to cooler climates. The Museum of Islamic Art, Doha, Qatar; Al Azhar Mosque; Abu Dhabi, and Sustainable City in Dubai also boast passive design. The Sustainable City spans over 113 acres. It has 500 villas, 300 tower houses and 1,500 apartments housing 3,000 residents. They use green roofs, shaded walkways and wind towers to reduce energy consumption eliminating the need for mechanical cooling and heating systems. Zero-Energy House in Japan and the Earthship Community in New Mexico are other examples of passive buildings that have achieved net-zero carbon and net-zero energy.

New buildings in Pakistan should embrace new technologies to not only mitigate heat but also to offset the buildup of greenhouse gases. The existing buildings too can neutralise the searing heat by retrofitting, says Anwar.

To retrofit existing buildings, better insulation can be added to keep the building comfortably warm or cool. Another way is to replace old windows with new, energy-efficient ones that help reduce heat loss or gain. Installing solar panels or green roofs can also generate clean energy and reduce reliance on traditional energy sources. Additionally, switching to LED or smart lighting systems can significantly reduce energy consumption and provide remote control capabilities. Upgrading to energy-efficient HVAC (heating, ventilation, and air conditioning) systems can also provide comfortable temperatures while using less energy.

Incorporating smart building technologies can optimise energy usage, water consumption and waste management. None of these technologies are a panacea in isolation. The balmy living conditions can only be achieved with a deliberate and conscious integration of green spaces into urban planning and development.

According to a study by UCLA Centre for Sustainable Urban Planning, 10-15 trees per block (approximately 1 acre) can reduce summer temperatures by 2-4° F (1-2° C). Another study by the University of Toronto suggests planting 20-30 trees per hectare to achieve a 1-2° C reduction in summer temperatures.

Environmentalist Rafi-ul Haq says “The number of trees required to offset the UHI effect depends on urban density and the quality of construction material, asphalt roads and concrete pavements.” As a rule of thumb, a 20-30 pc canopy/ vegetation cover can effectively mitigate the UHI effect, he says. Such new plantations and urban forests should be combined with the restoration and revitalisation of 450 odd, existing parks and green spaces in Karachi.

The city also needs around 50-100 new green spaces spread over 10-50 hectares, he says. Rafi says around 100-200 km of roads (within the populated areas), highways passing through and around the mega-polis, and other public spaces must be planted with local vegetation (trees and plants) to offset the growing heat.

Thick groves and large parks may not be possible in areas with high-density apartments and cluttered, small, plot-size 4-5 storey high buildings, enclosing narrow lanes and spaces in several parts of the downtown. “It is places like these that get blistering hot. The walls and roofs become very hot and there is little circulation of air amidst the high and single-storey houses,” says Iqbal Rana who lives in North Karachi. “Indoors are equally hot and humid. Living their during the heat waves exposes human body to relentless heat stress,” says Rana.

For places like these, Rafi says, vertical gardening and roof garden techniques with shrubs, climbers and potted plants should be undertaken. He says native heat-tolerant, drought-resistant species can create microclimates with cooler temperatures, providing relief from heat stress. “Pocket parks can be developed in small, unused triangles, circles or squares with shrubs, potted or other smaller plants. Similarly, median strips or sidewalks and narrow alleys can be utilised to create linear parks, park-lets or green corridors.”These solutions can help create green oases in dense built-up areas, improving air quality, mitigating awful heat and enhancing the quality of life.

New urban development must aspire to be resilient, sustainable, and livable. The focus should be on improving infrastructure efficiency and green infrastructure to keep the cities cool.

The writer is a senior staffer at The News