ACs making Kolkata hotter

KOLKATA: The gruelling summer has sent Kolkatans on an AC buying spree. Even as the CESC received a record 40,000 applications for installing air-conditioners in March-April, the cooling machines were actually making the city warm, pointed out experts. Night temperature in the city could have been a degree lower without the ACs, they claimed.
A study conducted by Centre for Environment and Development (CED) - a green NGO - says waste heat generated by ACs as a result of transferring heat from the interiors of a room to the outside has had a 'serious impact' on the ambient temperature of the city, especially at night.Upscale neighbourhoods where every household had an AC were the worst affected, it said. "Warm air yielded from air-conditioners generally rise up and disappear. But the cumulative effect of hundreds of them running and emitting warm air in a small area is a significant one. The accumulation of warm air can contribute to a rise in temperature. Our studies show that areas like Alipore, Ballygunge, Jodhpur Park, Gariahat, New Alipore and Park Street are warmer by at least a degree in the evening. Taking all the other warming factors into account, ACs has had an impact that can't be ignored," said AK Ghosh, director of CED.
'Heat-islands' have formed across residential areas of the city, Ghosh added. Radiation from material like concrete and bitumen are responsible for this. With more buildings in every locality, the number of radiating surfaces has gone up sharply. Due to a sharp shrink in the number of trees and water-bodies, the heat generated during daytime is not being absorbed quickly. It is being trapped in thickly populated areas, forming heat-islands.
The warmth generated by air-conditioners is adding to this, felt environmentalist Subhas Datta. "In the office-areas like Esplanade and Park Street, ACs are installed at a lower height and the hot air generated by them hits pedestrians. Not to mention the fact that they make the neighbourhoods warm. More importantly, 97% of the electricity consumed in West Bengal is generated by thermal power plants that use coal. The emission from the plants is constantly polluting the environment. So, the more ACs we use, the more we are polluting the air," said Datta.