The urban heat island effect is being exacerbated in Kolkata by the high temperatures and humidity that the city experiences before to the monsoon. The growth of the city’s built-up area has been reduced greenery and water bodies, exacerbating the heat problem.
With the monsoon still a few days away, Kolkata residents are experiencing daytime conditions akin to a pressure cooker, with a high temperature of 37°C and relative humidity close to 90%.
The heat island effect keeps the city from cooling down sufficiently, even after sunset, so there is no reprieve from the oppressive heat at night. On Sunday, the actual feel temperature in Kolkata was a blistering 55°C.
According to a study conducted by the environmental NGO Centre for Science & Environment (CSE), Kolkata is not becoming as cold at night as it did in the first ten years of the century.
“Kolkata has lost its ability to cool down at night due to an increase in built-up area, a decrease in greenery, and a reduction in water bodies,” stated Avikal Sombanshi of CSE’s Urban Lab.
According to experts, the impact of urban heat islands is greater at night than it is during the day. According to a CSE study, the core Kolkata regions that stretch from Dumdum in the north to Garia in the south have the lowest nighttime Land Surface Temperature (LST) drops. The average low temperature (LST) in the city core decreased from 32.5°C to 25.8°C at night between March 1st and August 30th, 2018 to 2023; in the outer city, it decreased from 31.6°C to 25°C, and in the periurban areas outside of Singur and Ashoknagar in the north, and Diamond Harbour and Kharagpur in the south, it decreased from 30.7°C to 27.4°C.
Kolkata’s urban heat island effect has gotten worse due to an increase in built-up area, a decrease in greenery, and the removal of water bodies.The city has the biggest built-up area among metro areas, with a rise from 70% of the total area in 2001 to 80.1% in 2023. As a result, the percentage of green space decreased from 15.2% in 2001 to 14.5% in 2023, the lowest percentage among metro areas.
Water bodies dropped from 5.1% of the total area to just 1.9% throughout that time.
According to a study by the environmental NGO Centre for Science and Environment, the urban heat island effect can increase local warming by up to 2°C, which lowers a city’s ability to adapt. High temperatures and humidity levels have the potential to impair sweating, the body’s primary means of cooling itself. Our bodies naturally cool when perspiration evaporates from the skin, but this cooling effect is diminished under higher humidity levels.
Because of this, individuals may get heat exhaustion and illness, and if the humidity is really high, the effects may be lethal even at somewhat lower temperatures, according to Avikal Sombanshi.
