While summer or pre-monsoon season this year has overtaken 2016 records as the second hottest pre-monsoon season in the country, winter and post-monsoon seasons are warming up faster, according to the latest findings by the Urban Lab of Centre for Science and Environment. According to the study, land surface temperatures in Delhi have been the highest since 2010 and the city recorded a significant positive anomaly (temperature higher than expected) on all three temperature parameters.
In a bid to understand the warming trend in a comprehensive way, the study by the Centre for Science and Environment (CSE) has analysed the temperature trends by covering all three dimensions of heat stress — surface air temperature, land surface temperature, and relative humidity (heat index). In Delhi, air temperature has been 1.77 degrees Celsius hotter than 2010, and the land surface temperature 1.95 degrees Celsius hotter, the study said.
According to the CSE analysis, the daily average heat index crossed 40 degrees Celsius in June, 2022. It said March and April have been unusually dry in Delhi, but humidity started to rise in May with some scattered rain spells. But this spike in humidity has led to an increase in the heat index in the city, indicating increased thermal discomfort among the population. “The highest land surface temperature was observed on May 16, 2020 when 53.9 degrees Celsius was recorded within city limits, followed by May 14, 2022 with maximum land surface temperature of 51.8 degrees Celsius. In the previous years, maximum land surface temperature was observed to be in mid-40s range,” the CSE findings said.
It further said during the heatwave in May, 2022, the land surface temperature across Delhi shot above 38 degrees Celsius, which was “unusual as the green pockets within the city have not heated up to this magnitude in the previous years,” and that the average land surface temperature has been getting higher than daily average air temperature. “Industrial and agricultural zone recorded highest increase in land surface temperature between March to May. The regions at the city periphery in the north, southwest, and northwest Delhi have seen the extremely high surface temperature rise from March 19 to May 14, 2022,” the study said.
The study further noted that even the temperature of the water bodies rose to 29-30 degrees Celsius in May, which were well below 27 degrees Celsius in March. According to CSE’s analysis on air temperature variation among city’s stations, Chandni Chowk recorded the highest average air temperature on May 14, 2022 with 40.39 degrees Celsius, followed by Punjabi Bagh at 40.29 degrees Celsius, Mundka at 39.5 degrees Celsius and Paharganj at 39.1 degrees Celsius.
CSE said the objective of the city analysis was to understand the combined effect of climate change induced unseasonal heatwaves. The study is based on comparative statistical analysis of temperature anomalies and observed heat-related impact in Indian cities and regions.