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Kharagpur: A new study by Nilabhra Mondal, a PhD student at IIT Kharagpur, and Dr. Prashant Anand, Assistant Professor in the Department of Architecture and Regional Planning, published in Nature Communications, identifies how patterns of urban growth establish future cooling demand. This study was done along with some researchers from the University of Calcutta, Arizona State University (USA), the National University of Singapore, University of Texas at Austin (USA), and the University of New South Wales (Australia). It has been believed that the combination of the increase in temperature with the increase in the demand for air conditioning, caused by climate change, is a worldwide phenomenon. This study disapproves of this belief. It associates the future cooling demand of urban areas not only with the increase in global temperature, but also with the patterns of urban growth over time.
Different cities have different patterns of growth. Some have rapid peripheral growth, some have vertical growth dominated by high-rise buildings and led by urban densification, and some have balanced and compact growth, while some have erratic and unorganized growth. These patterns of growth have a lasting impact on the city and the urban environment. As climate varies, so will cooling needs, but similar climates will have different cooling needs. Present and future heat burden is not just about climate. It is about the decades-long commitment of decisions concerning the placement of populations, the construction of buildings and the density of the urban fabric, the preservation of green spaces, and the expansion of the urban environment.
In this context, the study claims that cities have a kind of 'thermal memory.' The legacy of a city's development choices continues to affect the temperatures and the amount of energy needed to cool buildings, even today.
The study analyzed 88 Indian cities, including all the major metropolitan regions of Delhi, Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad, Ahmedabad, and Jaipur, using 20 years of satellite data and climate data for the years 2003 to 2023. The global sample was made up of 52 representative cities with different climates and urban forms. The cities of the U.S. were Dallas, Denver, Austin, Atlanta, Phoenix, Salt Lake City, Minneapolis, Chicago, Indianapolis, St. Louis, New York, Los Angeles, San Diego, San Francisco, Miami, Seattle, Boston, Baltimore, Portland, and Houston. The cities of Europe were London, Paris, Berlin, Madrid, Rome, Vienna, Milan, Budapest, Prague, Munich, Manchester, Brussels, Barcelona, Lisbon, Porto, and Athens. The cities of Asia were Kyoto, Tokyo, Osaka, Beijing, Wuhan, Shanghai, Guangzhou, Dhaka, Chattogram, and Singapore, and the cities of Australia were Canberra, Sydney, Melbourne, Brisbane, and Perth.
Cities undergoing rapid, sporadic growth are showing the highest rates of cooling demand growth. Medium-sized cities show some of the highest levels of absolute cooling demand. Beyond the effects of changing climate, vertical development and volumetric densification become critical in the estimation of cooling demand. Compact urban development, with a lower rate of increase in cooling demand as compared to urban development that has lower levels of built Form, indicates that building more compact cities, while still allowing for a high level of Urban density, will help mitigate the need for more energy in the future and the Urban heat Island Effect.
The analysis shows that cooling demand will continue to increase due to the impacts of climate change and Urbanization. In the future, climate change will become a serious threat if Urban development strategies do not consider the construction of Compact Urban Form combined with the use of Building density and height control to help moderate Urban growth while still considering the compactness of the city.
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