New Delhi, June 21: Mumbai is experiencing the biggest changes in nighttime temperatures, and India is enduring a severe heatwave. A new analysis on Friday showed that climate change added nearly 50 to 80 nights each year when temperatures exceeded 25 degrees Celsius, impacting sleep and health.

According to Climate Central and Climate Trends, climate change raises nighttime temperatures, affecting sleep quality and human health in India and globally. Nighttime temperatures are increasing faster than daytime temperatures due to climate change, mainly from burning fossil fuels.

India, highly vulnerable to the climate crisis, has seen a significant rise in minimum nighttime temperatures over the last decade. On June 18, Delhi experienced its warmest night in at least 12 years, with temperatures reaching 35.2 degrees Celsius, the highest since 1969.

Between 2018 and 2023, climate change added nearly 50 to 80 hot nights each year in cities across Kerala, Karnataka, Maharashtra, Tamil Nadu, Punjab, Jammu and Kashmir, and Andhra Pradesh. Mumbai saw the highest increase, with 65 additional hot nights. West Bengal and Assam were most impacted, with cities like Jalpaiguri and Guwahati experiencing 80 to 86 extra hot nights.

Several cities, including Jaipur, saw 15 to 50 additional hot nights due to climate change. Nighttime summer temperatures across India often exceed 20 degrees. Cities like Gangtok, Darjeeling, Shimla, and Mysore saw 26 to 54 more hot nights due to climate change.

Higher nighttime temperatures prevent cooling during the night, increasing health risks. Poor sleep from hot nights affects physical and mental health and life expectancy, especially for vulnerable groups like the elderly. This week, several Indian cities set new records for nighttime heat.

On June 19, Delhi broke its record for the highest minimum temperature, reaching 35.2 degrees. Between 2018 and 2023, Delhi had almost four additional nights over 25 degrees due to climate change. On June 18, Alwar in Rajasthan recorded 37 degrees, the highest nighttime temperature since 1969. Alwar experienced nearly nine extra hot nights due to climate change.

In Uttar Pradesh, Lakhimpur Kheri, Shahjahanpur, and Varanasi recorded their highest nighttime temperatures this week, with Varanasi seeing four additional hot nights from 2018 to 2023. These extreme nighttime temperatures contribute to heat stress and heat-related deaths.

The ongoing heatwave in India is intensified and made more frequent by climate change, according to studies by World Weather Attribution and ClimaMeter.

Roxy Mathew Koll, Climate Scientist, Indian Institute of Tropical Meteorology, Pune, said, "The urban heat island effect is most visible in the nighttime temperatures. Cities turn into urban heat islands when buildings, roads, and other infrastructure absorb and re-emit heat, causing cities to be several degrees hotter than surrounding rural areas. During the day, the sun's rays reach as shortwave radiation and heat the earth's surface. At night, the heat escapes as longwave radiation. While shortwave radiation can easily penetrate through and reach the surface, the longwave gets trapped easily by concrete and clouds."

On the other hand, Aarti Khosla, Director of Climate Trends, said, "Like day temperatures, night temperatures have also shown a constant and steady rise over the last few years. Warm nights have been punishing this summer with several cities shattering five decades of records. Cities will bear the highest brunt which will get worse due to the urban heat island effect. Several studies have already established that by the turn of the century, without very large reductions in fossil fuel burning, nighttime temperatures will not fall below 25 degrees in some places during hot weather impacting one's ability to recover for the next day. If we do not act now, nights will continue to be hotter, longer and sleepless, especially for the vulnerable."

(The above story first appeared on LatestLY on Jun 21, 2024 07:15 PM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website