The loss of green cover, diminishing green open spaces and the filling up of water bodies are making the heat more unbearable, said scientists.
Water bodies and green cover have a cooling effect whereas concrete and built-up areas trap and radiate heat back.
Studies have shown urban areas with more concrete construction are hotter than peri-urban or rural areas with more green and blue cover, said Arpita Mondal, an associate professor of civil engineering and climate studies at IIT Bombay.
Kolkata lacks a heat management plan. The authorities should prepare one and implement measures throughout the year to make the city heat-resilient, said scientists.
“Carbon emissions and burning of fossil fuels have resulted in climate change and heating of the earth. We will continue to see high temperatures and heatwaves. The absence of a blue and green cover has aggravated the impact of the warming,” said Mondal.
“Water bodies can absorb and store heat, resulting in cooling of surroundings. Open green spaces, too, can help in cooling the surroundings. On the contrary, their reduction can lead to more heating of the surroundings,” she said.
The difference in temperatures between urban and rural areas is more pronounced at night. “The heat that is trapped by concrete is slowly released after sundown. In rural areas, with more trees and water bodies, this release of heat after sunset is much lower,” said Abhiyant Tiwari, lead (climate resilience and health) at NRDC India.
The Intergovernmental Panel on Climate Change (IPCC), a United Nations panel, in its sixth assessment report (AR6 Synthesis Report) published last year said “human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming, with global surface temperature reaching 1.1°C above 1850–1900 in 2011–2020”.
Kolkata is in the grip of a heatwave now and no rain seems to be in sight in the near future. “Severe heatwave conditions” are likely in the other districts of south Bengal, the Met office has forecast.
The maximum temperature recorded in Alipore on Friday was 40.8 degrees Celsius, five notches above normal. On Saturday, it was 40.2 degrees.
The Telegraph reported earlier this month that the minimum temperature in most of Bengal had increased in the past 50 years, an analysis of daily temperatures recorded in the state between 1969 and 2020 has shown.
The “preliminary analysis” by scientists at ISI Kolkata also showed a rise in temperatures recorded in Alipore and Dum Dum.
State government officials conceded that large tracts of water bodies along VIP Road, water bodies to the east of EM Bypass and elsewhere had been filled up, often illegally. Buildings have come up in their place.
“EM Bypass was once a road lined with trees. It is now a barren road with hardly any tree cover,” said a Salt Lake resident.
The Kolkata Municipal Corporation has planted nearly 70,000 saplings in the past two years, said an official. Some of these are saplings that will have a canopy when they grow, but that will take years.
“The civic authorities should be stringent about protecting water bodies. They should look for open spaces and increase green cover. They should also prepare a comprehensive heat management plan and implement measures around the year,” said Anumita Roy Chowdhury, executive director of the New Delhi-based Centre for Science and Environment.
A heat management plan aims to reduce heat stress for a city’s residents and involves long-term urban planning strategies. The measures include greening a city, protecting water bodies, making shaded areas, among others. A heat management plan helps make a city more resilient to rising temperatures.
A state government official said they were preparing a climate action plan and it would include heatwave management.