Bhubaneswar: Even as a severe heatwave continues to grip India, a recent global study has revealed that the number of warm nights in cities has surged by 32 per cent (pc) in the last decade due to climate change. It showed climate change leading to rise in nighttime warming and seriously impacting sleep and human health.

The new analysis by non-profit Climate Central and consulting initiative Climate Trends https://www.climatecentral.org/report/sleepless-nights shows that Indian cities saw an additional 50 to 80 nights every year between 2014-2023 with temperature exceeding 25 degree Celsius. Around 300 Indian cities with populations of over 100,000 were covered under the study.

As per the analysis released on June 21, approximately 50 to 80 days each year were added above this threshold by climate change in cities across Kerala, Karnataka, Maharashtra, Tamil Nadu, Andhra Pradesh, Punjab and Jammu and Kashmi between 2018 and 2023. Most impacted were regions like West Bengal and Assam where cities like Jalpaiguri, Guwahati, Silchar, Dibrugarh and Siliguri experienced on an average between 80 and 86 additional days each year above the 25 degree Celsius threshold due to climate change.

Among metro cities, Mumbai witnessed the highest changes in the night-time temperatures, with an additional 65 days of warmer nights due to global warming.

Several cities across India saw between 15 and 50 additional days where the minimum temperatures exceeded 25 degree Celsius due to the influence of climate change, including Jaipur, with an additional 19 hot nights.

In both observations and counterfactual climate, the nighttime summer temperatures across India often exceeded 20 degree Celsius over the entire summer period.

The cities that had the largest number of days where the minimum temperature exceeded 20°C due to climate change are Gangtok, Darjeeling, Mysore and Shimla with an average of 54, 31, 26, and 30 days added by climate change, respectively. Overall, 16 cities crossed 25°C for 920 days during the period and 11 other cities during 919 days. The list includes metros like Chennai and Kolkata as well as cities like Port Blair, Puducherry, Puri, Surat, Visakhapatnam and Patna among others.

The figure is a benchmark for an unusually heated night, as sleep gets disturbed above that limit. “Hot nights make it harder for people to recover from the heat of the day, with wide-reaching and severe consequences. There is growing evidence that as night-time temperatures rise, human sleep is being eroded around the world (with) a range of associated impacts,” the report stated, while indicating that air pollution too has a role to play in the changing patterns.

The study, which considered 24 global climate assessment models, pointed out that the average number of nights with 25°C or above comes down to 543-175 days and a whopping 32 per cent less if climate impact is taken out of the equation.

Sources from the India Meteorological Department too corroborated the findings with former director general KJ Ramesh sharing that the latest IPCC AR 6 reports too subscribe to the trend.