New Delhi: Concretisation and rising humidity levels are putting India's megacities under severe stress, with nights no longer getting cooler than they were a decade ago, according to a new report by the Center for Science and Environment (CSE).
CSE analyzed summer air temperature, land surface temperature and relative humidity data for six megacities – Delhi, Mumbai, Kolkata, Hyderabad, Bengaluru and Chennai – from January 2001 to April 2024.
The think tank found that increased humidity is exacerbating heat stress across all climate zones, even causing a slight drop in air temperatures in Delhi and Hyderabad.
Except for Bengaluru, summer average relative humidity in the other five megacities has increased by 5-1 per cent over 2014-2023 compared to the 2001-201 average.
The CSE report comes at a time when extreme heat is affecting health and livelihoods across large parts of India.During the summer of 2001–2010 land surface temperatures would drop by 6.20–13.20 °C from daytime peak to nighttime minimum. CSE said that in the last 10 summers (2014-2023), the night time coolness has decreased to 6.20-11.5 degrees Celsius.
“Hot nights are just as dangerous as extreme afternoon temperatures. Somvanshi said that if the temperature remains high at night, people get little chance to recover from the heat of the day.
A study published in 'The Lancet Planetary Health' said that the risk of death from extremely hot nights could increase by almost six times in the future.“This prediction far exceeds the daily average mortality risk from warming suggested by climate change models,” he said.
The study said rising humidity levels have made the monsoon season in Delhi, Mumbai, Kolkata and Chennai hotter than the pre-monsoon period.
It says that all megacities have become more compact over the past two decades, increasing heat stress. CSE highlighted that increasing green cover is not effective in reducing night heat.
The study revealed that Kolkata has the highest percentage of land under concrete and the lowest green area among metropolitan cities, while Delhi has the lowest percentage of land under concrete and the highest green area.There has been a decline in green cover in Mumbai, Kolkata and Chennai. Chennai's built-up area has doubled in the last two decades, while its green cover has declined by about 14 percent.
CSE analyzed summer air temperature, land surface temperature and relative humidity data for six megacities – Delhi, Mumbai, Kolkata, Hyderabad, Bengaluru and Chennai – from January 2001 to April 2024.
The think tank found that increased humidity is exacerbating heat stress across all climate zones, even causing a slight drop in air temperatures in Delhi and Hyderabad.
Except for Bengaluru, summer average relative humidity in the other five megacities has increased by 5-1 per cent over 2014-2023 compared to the 2001-201 average.
The CSE report comes at a time when extreme heat is affecting health and livelihoods across large parts of India.During the summer of 2001–2010 land surface temperatures would drop by 6.20–13.20 °C from daytime peak to nighttime minimum. CSE said that in the last 10 summers (2014-2023), the night time coolness has decreased to 6.20-11.5 degrees Celsius.
“Hot nights are just as dangerous as extreme afternoon temperatures. Somvanshi said that if the temperature remains high at night, people get little chance to recover from the heat of the day.
A study published in 'The Lancet Planetary Health' said that the risk of death from extremely hot nights could increase by almost six times in the future.“This prediction far exceeds the daily average mortality risk from warming suggested by climate change models,” he said.
The study said rising humidity levels have made the monsoon season in Delhi, Mumbai, Kolkata and Chennai hotter than the pre-monsoon period.
It says that all megacities have become more compact over the past two decades, increasing heat stress. CSE highlighted that increasing green cover is not effective in reducing night heat.
The study revealed that Kolkata has the highest percentage of land under concrete and the lowest green area among metropolitan cities, while Delhi has the lowest percentage of land under concrete and the highest green area.There has been a decline in green cover in Mumbai, Kolkata and Chennai. Chennai's built-up area has doubled in the last two decades, while its green cover has declined by about 14 percent.
