Urbanisation-led warming highest in Delhi-NCR, Jaipur, Ahmedabad and Pune: Study

A study led by researchers from the School of Earth, Ocean and Climate Sciences at IIT Bhubaneswar found a higher warming rate over cities in the northwest, northeast and southern India.

Delhi-NCR, Jaipur, Ahmedabad, Pune, Bengaluru, Patna, Nashik and Raipur have been ranked among the top Indian cities to have significantly warmed due to urbanisation-driven changes and living conditions during the last two decades, a new study has found.

The findings come in the backdrop of several cities in the country recording 46 degrees Celsius or more for consecutive days this week. While on Wednesday, a weather station in Delhi recorded a maximum temperature of 52.9 degrees Celsius, on Tuesday, Jaipur witnessed the seventh warmest day in May in 123 years with a temperature of 46.6 degrees Celsius. Breaking all previous records for May, Agra on Tuesday recorded 48.6 degrees Celsius.

During each decade between 2003 and 2020, the highest warming due to urbanisation was experienced in Ahmedabad, Jaipur, Rajkot, Delhi-NCR, Pune, Lucknow, Agra, Bengaluru, Nashik, Hyderabad (see table). Whereas, increased warming due to relative urban effect (with contribution from regional factors) was found high across Pune, Raipur, Jaipur, Ahmedabad, Patna, Nashik, Ludhiana, Lucknow, Bengaluru and Vadodara between 2003 and 2020.

These results were discussed in the latest study in Nature Cities journal led by researchers from the School of Earth, Ocean and Climate Sciences at IIT Bhubaneswar.

The rapidly changing urban landscapes were found to be a hindrance in bringing about the effect of evaporative cooling. Instead, unchecked urbanisation was accumulating heat within the cities due to factors like growing concrete jungles, lack of green spaces and heightened anthropogenic activities, thereby creating urban heat islands within these cities.

Urban heat islands refer to small localities where temperatures are higher than neighbouring areas.

This year’s summer has been exceptionally hot. Overall, night temperatures recorded have remained higher than normal. This has added to the heat stress levels experienced in both urban and rural areas, making it an unpleasantly hot and humid summer rather than a hot and dry season, which is otherwise experienced over India during March-June.

Since April, various parts of the country have been experiencing extended heatwave days. Some spells even lasted up to 15-17 days as experienced over Odisha and Gangetic West Bengal. Subsequently, hotter weather associated with severe heatwave conditions has been prevailing over western Rajasthan and Gujarat and adjoining north India regions, where heatwave conditions have been ongoing since May 16.

With such scorching heat and heat stress levels, the demand for air conditioners, coolers and fans has grown and electricity consumption has touched record peaks in the recent weeks in many areas in the country. And its downside was reflected in the form of emissions and greenhouse gases, which added to the increased heat effect, the study noted.

“Urbanization and the associated energy demands resulted in the production of greenhouse gases and associated emissions, contributing to climate change,” the study highlighted.

Cities recorded higher night-time surface temperatures with a mean rate of increase of 0.53 degrees Celsius/decade (+/- 0.19 degrees Celsius) from 2003 to 2020. Overall, most parts of India had warmed at a mean rate of 0.26 degrees Celsius/decade (+/- 0.27 degrees Celsius).

Further, the study found an increased warming over cities in northwest, northeast and southern India than in other parts of the country. An estimated 37.73 per cent of the total urban warming was linked to urbanisation. This warming trend was significantly higher in the rapidly growing cities located in eastern and central India, the study concluded.

From 2003 to 2020, cities get warmer