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Several Tier-II Indian cities like Jalandhar, Patiala, Hisar, and Erode could experience an additional warming up to 0.7-0.8°C, compared to their surrounding rural areas, under a 2°C global warming scenario. This is according to new research led by the University of East Anglia (UEA) in the United Kingdom (UK).
The study, published in the journal Proceedings of the National Academy of Sciences (PNAS) on February 4, analysed future temperature trends in 104 medium-sized cities (with population between 3,00,000 and one million) in tropical regions in Asia including in India and China, South America, the Middle East, USA, and Africa.
In the five largest cities by population, the greatest changes were seen in Jalandhar in India, Fuyang in China and Kirkuk in Iraq, which experienced 0.7-0.8°C additional change in temperature compared to their rural surroundings.
Other cities experienced significantly greater warming, for example Asyut (Egypt), Patiala (India) and Shangqiu (China), which experienced 1.5-2°C additional change, which is up to 100 per cent more than their hinterlands, the study found, using advanced climate projections machine learning techniques.
Overall, out of the 104 cities, day-time land surface temperatures in 81 per cent were predicted to warm more than surrounding rural areas. In 16 per cent cities, mostly in India and China, the additional warming may be 50 to 112 per cent as much as the warming in surrounding areas under a 2°C global warming scenario, which was likely to be reached in the second half of this century.
The Indian cities analysed in the study were — Jalandhar, Bikaner, Patiala, Hisar, Mathura, Erode, Bijapur, Parbhani, Nanded Waghala, Akola, Muzaffarnagar, Rohtak, Bathinda, Khammam, Shahjahanpur, Mathura, Gaya, and Satna.
Many cities are often warmer than rural areas due to the urban heat island phenomenon, which is caused by dense infrastructure built with asphalt and concrete that absorbs solar heat, lack of vegetation for cooling, and waste heat from human activities like air conditioning. The study pointed out that this heat will be intensified because of regional change in climate and vegetation cover, further leading to increased heat-related health risks for urban populations.
Apart from the population, the cities in the study were selected on the basis of features like over 100 km distance from shoreline and more than 50 km proximity from lakes.
“This analysis shows even state-of-the-art projections likely underestimate future urban warming. For example, our results suggest that several cities in North-East China and northern India are projected to warm by 3°C, despite Earth System Model projections of their hinterlands showing a warming of 1.5-2°C,” said co-author Manoj Joshi, from the Climatic Research Unit at UEA.
The research was led by Sarah Berk from UEA’s School of Environmental Sciences. The team excluded cities in mountain and coastal regions to remove influences of features such as hills, lakes and oceans, to ensure they captured relationships based on physical processes related to climate, rather than other differences.