Can we make Dhaka cooler?

July last year was the world's hottest month. It is only a two months' wait to see how this July will look like. But Asian cities are already feeling the wrath of summer. Dhaka has seen its highest temperature in years, Chuadanga has been the hottest town in Bangladesh for two weeks now. 

Not only in Asia or Africa, cities are getting hotter everywhere. Average summer temperatures are predicted to soar above 35°C in both hemispheres in the next 20 to 40 years. This prediction is about average temperatures, but cities are already witnessing much higher temperatures. Dhaka has seen temperatures crossing 40°C, while some Middle Eastern cities saw mercury rising to 50°C.

Cities cannot be made heat-proof, but they can get cooler. Many tools are on trial worldwide to reduce impacts of intense heat. As heat intensifies, pro-active authorities are in search of ways to cool their cities. Dubai has made artificial rain, Dhaka has joined other Asian cities in spraying water on roads.

Some of the initiatives are for bringing immediate relief from torrid heatwaves, some are long term.

Here are some tools global authorities are trialling to cool their cities.

Using water as a tool to cool

Use of water in cooling system can be traced back to centuries. Alhambra, a 13th century palace in Spain, had pools and fountains to keep the inside environment cool.

Water is still a saviour to stay cool. Over the century, Dhaka city has destroyed its natural water cooling system. It polluted its rivers, killed its canals and filled ponds to build buildings. Now it is spraying expensive Wasa water to cool the city streets.

Bangladeshi architect Rafiq Azam, who helped Dhaka South city revive some of its almost-abandoned parks and playgrounds, says he always keeps water at the centre of his landscape designing, not for cooling impact alone, but for it being the lifeline for humans, trees, and birds.

As the severe heatwave raises the city's temperature to 39°C or more, the Dhaka North city authority launched a programme of spraying water on roads in selected spots to give people on the city streets some relief from the sweltering sun.

It was a pleasant surprise for people in the city's Agargaon to see water cannons showering rain in the streets.

The Dhaka north city has put two of these large spray machines in service, its Mayor Md Atiqul Islam said. Each vehicle can spray about 400,000 litres of water per day. Dhaka South City Corporation has also increased its water spraying efforts.

Spraying water mist from large fog gun trucks to cool a city area is commonly practiced in cities around the world. China's cities of Hangzhou, Wuhan and Chongqing used such fog gun trucks and mist cannons when temperature soared to record high two years back.

The Dhaka North mayor said they are taking measures following recommendations from the corporation's chief heat officer.

Dhaka is one of many woefully unprepared cities that are waking up to the perils they knew long before and ignored so far to take prompt steps to minimize "heat island" impacts.

Now, the Bangladesh's capital city, sweltering in the hellish summer, joined the global cities appointing "chief heat officers" and engaging them in devising appropriate "heat action plans." In May last year, Dhaka North City Corporation appointed Bushra Afreen as its first chief heat officer under an urban heat resilience scheme in association with the Arsht-Rock Foundation. Some other foreign cities also got CHOs under the same programme.

Under the initiative, Dhaka North city has planned to plant two lakh trees to control heat. The mayor requested city people to take care of trees in their surroundings. He also asked his officials to create "artificial rain" (he in fact meant spraying water) in parks and playgrounds in the city within a week as heatwave continued.

The efforts are being taken now when the Dhaka city has destroyed its greenery. Most of its canals now exist only in old city map.

Green areas like parks, playgrounds, and urban forests – crucial for controlling temperature in a city – have shrunk 66% in the Dhaka north city over the last three decades, according to a 2023 study.

"The way Dhaka's green space is shrinking day by day, there will be no greenery in Dhaka after a while. Dhaka South has less green space than that in Dhaka North," said one of the researchers of the study Farhadur Reza, Associate Professor of Urban and Regional Planning Department of Jahangirnagar University.

So, the city people will have to wait to see the impacts of its tree plantation drive. Until then temporary measures like spraying water during intense summer days are the only options since the lost canals and ponds would never be revived.

Dhaka city may try some other temporary steps as in other cities.

Spreading awnings overhead

City authorities and market associations can think of rolling out large canvas awnings supported by a frame that connect buildings on both sides of a road to shield shoppers and pedestrians from torrid sun. CNN shows Seville city of Spain and Tel Aviv of Israel expanded such awnings in schools, playgrounds, hospitals and business districts.

Using portable pools

City authorities can keep portable rubber pools of water in parks, playgrounds and public places for people to wash their faces, even take a bath. Corporates, clubs, community organisations can also join such initiatives.

 In Palestines's Gaza, children were seen bathing and playing in water in a portable pool during severe summer heat last year. This summer is worse for Palestinians. Most of Gaza is in ruins today amid Israel's attacks, leaving thousands killed, thousands of others homeless in scorching heat. Gaza is in humanitarian crisis. People there need water, food, shelter, everything.

Creating tree-lined streets

Dhaka city needs some breathing spaces like Ramna and Hatirjheel, with streets and pavements under dense shade of trees. Newly-built Kuril-Purbachal road, known as 300-ft road, can be one such tree-lined roads. Rajshahi city has transformed itself with trees in just a few years, it protected the river bank along the Padma, created long walkways, planted trees there. Rajshahi is experiencing temperatures above 40 °C, it would be higher if there were fewer trees.

These are relatively simpler, less expensive tools to bring some relief during severe heat, instantly or in years. There are durable options practiced by some cities, which could be less viable for Dhaka right now because of the time and money involved.

These involve changes in engineering and architectural designs, as the way the city is. built and the materials used—all make the city hotter every day. The changes would be costlier for a city like ours, some even might sound impractical right now for Dhaka city authorities. But these are in practice somewhere in the world and yielding the desired results.

Here are some tips:

Garden city, skygarden

Dhaka cannot rebuild its park and greeneries it already destroyed. Creating new park does not appear in expansion plans of city authorities and private developers. What they can do at the most is planting few hundred trees here and there. Obviously, any number of trees will provide some shade at least in parts of the city.

However, city authorities need to think a step further to develop greeneries in whatever space is still left usused. The Guardian Cities draws example from Singapore. The city-state's intensive "garden city" initiative taken in 1967 created greenery and new parks. Squeezed for space, it has focused on vertical plantation—skygardens, green roofs and green walls. It introduced new urban space regulations requiring a new high-rise building to have greenery—either at ground level or at height-- of the same size of the development site.

Painting buildings and footpaths white

Painting rooftops, buildings and pavements can be another defence against the summer heat. Some cities tried it, using newly developed "ultra white" paint that can reflect 98% of sunlight and make a building's surface cooler by 20 degrees Fahrenheit at night or by 8 degrees during daytime, a CNN report says. New York had also cool roofs initiatives, with city authorities installing roofs with while reflecting coating free of cost in public buildings and some other structures. Research by NASA suggest a white roof can be 23 °C cooler than a typical black roof in summer days in New York. For Los Angeles, black roads are a challenge as black asphalt covers 10% of the city, absorbing 95% of the sun heat and contributing to the urban heat island impact.

An Australian research on low carbon living says conventional paving can reach temperatures up to 67 °C and conventional dark roofs can be as hot as 50-90°C in summer days, posing significant health risks.

Using cool coatings such as lighter pigments in asphalt or white-gray paint in roads and roofs can help reflect more solar heat from the city.

Changing designs

Conventional building methods are environment-friendly everywhere in the world. In our land, rural houses with mud or bamboo walls and straw or tally roofs are naturally cool. But it is absurd for any city to go back to such traditions. What is needed is changes in architectural designs so that, as architect Marina Tabassum puts it, a building can "breathe without artificial aids."

The Bangladeshi architect, who in April was named in the Time100 Most Influential People of 2024 for her unique and innovative designs, prioritizes local cultures and values in architectural designs, while taking care of environment. Bait Ur Rouf Mosque in Dhaka stands as a unique example of her works.

Middle Eastern shading device, mashrabiya, has been in use in Abu Dhabi to shield buildings from harsh desert heat.   These traditional wooden screens allow filtered light inside while protect dwellers as they cut a building's carbon emissions by 20%.

Cities are warmers by 2 to 10°C than surrounding areas. By 2050, about 70% of the world's people are expected to live in cities. More people will mean more buildings, more destruction of nature, more heat. This is the future of cities.

City authorities that really value wellbeing of residents recognise the need for urban cooling and try all possible options to minimise heat island impacts as they build markets, high-rises, flyovers. Dhaka may choose to be one of them, or stay out.