Dhaka turning into ‘heat island’: Study

The people living in the capital city Dhaka were in extreme discomfort due to severe heatwave almost throughout the month of April.

However, those living in the greener areas around the capital were living in a relatively cooler weather.

A large section of residential and commercial areas in Dhaka has turned into a “heat island” which has created this difference in the land surface temperature between Dhaka and the surrounding areas.

The highest difference in temperature is 7 degrees Celcius.

These were said in a research article ‘Changes in urbanisation and urban heat island effect in Dhaka city’ in Springer’s Theoretical and Applied Climatology in February 2022.

The article said the day and night temperature differences at the Dhaka city’s warmest location and the coolest point outside the city were nearly 7°C and 5°C, respectively.

It’s like when the temperature in Savar or Singair in Manikganj is 30°C, the temperature in Dhaka’s Tejgaon or Farmgate area at that time would be 37°C. At the same time, such difference in temperature is also seen inside Dhaka too.

For example, the temperature in the zoo and botanical garden areas in Mirpur is 5°C cooler than Gulshan at the warmest period of a day.

Shamsuddin Shahid, associate professor at Universiti Teknologi Malaysia, Mohammad Kamruzzaman, senior scientist at Bangladesh Rice Research Institute (BRRI), ASM Shanawaz Uddin of civil engineering department at Ahsanullah University of Science & Technology, Najeebullah Khan of Lasbela University of Agriculture, Water & Marine Sciences in Baluchistan and Abu Reza Md Towfiqul Islam of disaster management department at Begum Rokeya University, Rangpur conducted the research.

Speaking to Prothom Alo on Sunday, Shamsuddin Shahid, who led the research, said the temperature in Dhaka has been rising fast for the last few decades. It is possible to bring the temperature down by several degrees simply by planting trees by the footpaths and on roofs and reclaiming the waterbodies which are turning into dumping yards.

Research team’s member Mohammad Kamruzzaman said a large part of Dhaka city has turned into heat island. Trees have to be planted by the walkways and open spaces in the areas, and gardens have to be made on roofs.

"Besides, we have to excavate waterbodies in the city," he added.

The warmest heat islands in Dhaka are Tejgaon, Farmgate, Karwan Bazar, Paltan, Motijheel, Gulshan, Banani, Rampura, Banasri and Madani Avenue. These areas are followed by Uttara, Mirpur and Shewrapara.

The research reveals that the land surface of Dhaka city has been expanded by 25.33 per cent between 2001 and 2017. At that time the population in the city increased by 76.65 per cent.

Mohammad Kamruzzaman said the expansion in land surface means the green areas and waterbodies in the Dhaka city have decreased at that time while population and houses have increased. In some areas inside the Dhaka city the temperature has increased by 3°C on average than the peripheral areas in just 17 years due to unplanned urbanisation and rise in number and density of population. The warmest periods in Dhaka city are in March, April and May.

The research also says that the Dhaka city was heavily expanded in 2007 and 2008. The land surface area was expanded by 6.1 per cent that time. The population density in Dhaka was 9,481 in 2001 which has increased to nearly 13,000 in 2017.

Dhaka North City Corporation (DNCC) has already taken steps to decrease the impact of heat island. Speaking to Prothom Alo, DNCC mayor Atiqul Islam said, “We will plant some 200,000 saplings in Dhaka city to bring the temperature under control here. We have appointed an officer in this regard at the assistance of the Rockefeller Foundation, USA and Dhaka University. We hope with the help of all the temperature could be brought under control.”

The observations of Bangladesh Meteorological Department say Dhaka experienced heatwave in 25 of the first 29 days of April this year. Dhaka was almost always warmer by 2-4°C than the surrounding districts.

A research has been going on Dhaka’s temperature in April this year. Shabbir Ahmed, professor of Department of Architecture at Bangladesh University of Engineering and Technology (BUET) is leading the research team. The primary findings of the research reveal the temperature in most of the areas of Dhaka was between 40 and 42°C in almost the whole April. That means Dhaka experienced severe heatwave in April. The risk of fire is also high in areas that are hotter than other areas in Dhaka due to the heatwave.

Speaking about this to Prothom Alo, Shabbir Ahmed said Dhaka has seen unplanned urbanisation. Green areas and waterbodies have almost been destroyed completely. As a result, almost the whole city has turned into a heat island. This has created an environment which is extremely unhealthy and uncomfortable for the city dwellers. Even the air in the city has become hotter. The situation will worsen if sufficient forestation is not achieved in Dhaka, he added.

* The report has been rewritten in English by Shameem Reza