Climate scientists have said that unplanned urbanization, especially unplanned infrastructure and buildings in city areas, changes in air movement, humidity, radiation and various climate-related factors are the main cause of increasing heat sufferings in Bangladesh.
"During this April when the temperature rises to 33 to 35 degrees Celsius, we felt extreme heat, this is the outcome of the changes in air movement, humidity, radiation and various climate-related factors, if the temperature in any area is 35° Celsius and this remains for six hours at a stretch, this should be called extreme heat," Dr. Shamsuddin Shahid, professor at the Department of Water and Environmental Engineering at the Universiti Teknologi Malaysia (UTM) said.
One thing is very important to discuss heat that is humidity, if the humidity in the air is high along with the heat, then the feeling of heat increases. In areas where there are more concrete structures, the daytime sunlight is stored there. The stored heat added to the heated air increases the feeling of heat, he said.
However, as a result of rising heat, by 2030 Bangladesh could lose about nearly 5 per cent of its total working hours, equal to 3.83 million full-time jobs and GDP losses of 4.9 per cent, Mujib Climate Prosperity Plan 2021 said.
In 2022, Dhaka was seen as the seventh least livable city in a global ranking by the Economist Intelligence Unit, and was the fourth placed mega-city facing the biggest challenges in another index by the Institute of Economics and Peace, due to its booming population, high disaster risk and loss of green spaces.
"Nowadays, we use the term "Heat wave", actually a heatwave is a wave of heat crossing over various regions of the world. This is seen as a heatwave in whichever region it is prevailing. This summer is becoming dangerous for the people of the entire South Asia including Bangladesh. Around 66 per cent of the people in South Asia are at risk of the Wet-Bulb Globe Temperature. In every decade between 1979 and 2021, the number of such hottest days during summer is increasing from one day to three days, Shamsuddin Shahid explained.
According to him, there is a heatwave prevailing in most areas of East and South Asia, the temperature in several cities of India is even higher than in Dhaka now. The highest temperature in Bangladesh remains between 40 to 42 degrees Celsius. However, in Odisha, West Bengal and Bihar, the temperature has soared up to 43 to 45 degrees. Even Malaysia, Laos and China remain above 40 degrees Celsius at this time. While the temperature in Dhaka is lower than these cities, the heat is felt more here. The reason behind this is unplanned urbanisation more than climate induced.
"Dhakas land surface temperature increased by a mean of 6.43 degrees Celsius, or 0.24C per year, from 1993 to 2020, causing serious heat stress for residents," according to a 2021 study by Md Imran Hosen, a climate researcher at Australias University of New South Wales and a group of researchers that measured how changes in the use of space have fueled heat-related troubles in the city.
Md Imran Hosen said Dhakas built-up area expanded by 67 per cent between 1993 and 2020, covering low-lying land, green and open spaces and water bodies. That has led to the loss of 56 per cent of green space in just three decades.
"Concrete buildings and paved ground trap, absorb and radiate heat, creating a "heat shell" effect whereby the temperature in the city is a few degrees Celsius higher than in surrounding rural areas with more greenery and fewer people, he explained.
Focusing on the solution of these prevailing situations, Professor Dr Shamsuddin Shahid said Singapore as an example here, large buildings are constructed on either side of the streets, taking the wind direction into consideration. This facilitates air movement further. Also, after the buildings are constructed, plants and trees are planted on the roofs, walls and in the surrounding vicinities to lower temperatures.
"Singapore City Corporation has made a rule that at least 80 per cent of the areas of the paths where people walk must have trees so that they people can have shade when they walk. By these initiatives they have managed to lower the temperature of the cities by 3 to 4 degrees Celsius less than the areas by the sea in Singapore," he continued.
The Indian government has made an arrangement for bathing and drinking water at the bus stands, railway station and other public places. The slum-dwellers of the cities, the taxi drivers, hawkers and other low-income people could come and use these facilities. Such small initiatives make it possible to protect people from the high temperatures in the cities, unfortunately there is nothing like that, Bangladesh is constructed in the cities, leaving no space for air flow, no trees and no water points thus increasing the heat suffering.
A major concern is how a megacity like Dhaka - accounting for more than one-tenth of the national population - can provide a decent environment for its residents as their numbers rise.
Afsana Haque, professor of urban and regional planning at the Bangladesh University of Engineering and Technology (BUET), said Dhakas environmental troubles are related to its rapid, unplanned growth pattern.
The explosion in the urban population has contributed to the shrinking of healthy green spaces, from 17 per cent of the citys area in 1989 to only about 2 per cent in 2020, according to a study published in the journal Environmental Challenges.
Dhakas land surface temperature increased by a mean of 6.43 degrees Celsius, or 0.24C per year, from 1993 to 2020, causing serious heat stress for residents, according to a 2021 study by Hosen and a group of researchers that measured how changes in the use of space have fueled heat-related troubles in the city.
Dhaka and Chattogram are becoming champions on chopping down the trees, filling up water bodies and carrying out totally unplanned urbanisation, these cities have been made into heat shells; however, it is extremely difficult to create water bodies anew in the cities. But trees can be planted. Planting a few thousand trees in the city will do no good. Trees must be planted along all the footpaths of the cities and in 20 per cent of the new residential areas. We have to go in that direction. Sprinkling water in the roads is just a temporary relief, this is not a solution. Cooling points must be set up at various intervals along the roadsides, the experts said.
