Dhaka’s land surface temperature increases alarmingly, study finds

Dhaka city’s Land Surface Temperature (LST) has increased 4 to 5.5°C in the last 18 years and the warmest surface of the city is in Bhatara, according to a study done by Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU).

Urban planner Akter Mahmud told Prothom Alo, climate changes significantly and natural calamities such as high tide and cyclone strike due to only 0.5°c rise in temperature. Only 1°c LST increase creates heavy disruption in people’s lives.

So, 4 to 5°C increase of LST in Dhaka city is alarming and is bound to cast a negative impact on people’s daily lives, he added.

About such massive increase in Dhaka’s LST, experts said that a city cannot be filled only with building as it requires appropriate portions of cultivating land, greenery and wetlands.

But Dhaka city has lost its arable land long ago, most of the wetlands are filled and LST has increased.

Mahbuba Mehrun, a post graduate student of the department of Agroforestry and Environment of BSMRAU, has done the related thesis under the supervision of Hasan Mohammad Abdullah.

They analysed satellite images in the university’s GIS and Remote Sensing to conduct the thesis.

The thesis titled ‘Monitoring the spatiotemporal dynamics of wetland in Dhaka city’ said, the lowest and the highest LST of Dhaka city was 9.96°C and 24.11°C respectively in 1990. Lowest and highest LST was 14.71°C and 23.25°C in 2000.

After 18 years, in January 2019, lowest LST increased to 18.80° and highest increased to 28.78°C.

Supervisor of the thesis Hasan Mohammad Abdullah said that factors such as global warming, rise of built-up area, decline of wetlands and population density are to blame for increased LST.

Decrease of wetland contributed most in land surface temperature increase, he said.

In 1990 wetland consisted of 11.28 per cent area of the Dhaka city while only 8 per cent lands were built-up area. But built-up area increased to 38.26 per cent and wetland reduced to 6 per cent in 2015, the study observed.

In 1990, temperature of at least 80 per cent of Dhaka city’s land was 15-18°C. Over 80 per cent of city’s surface is now 21 to 30°C warm.

Asked about the impact of LST increase in citizen’s daily lives, Hasan Mohammad Abdullah said, rise in surface temperature contributes to increase in overall temperature of the city. It also triggers many health concerns of the citizens.

People incur financial setback due to increase in temperature as the use of electric fan and air conditioner increases as a result, he added.

Hasan Mohammad Abdullah warned that Dhaka will be further unlivable in future if this trend of LST increase continues.

He suggested preservation of remaining wetland, greenery, and open space to prevent further increase of Dhaka’s surface temperature.

Roof gardening can also contribute to keep the temperature in check. If possible everybody should do gardening on roof tops where possible, Hasan added.