The impact of climate change on Indian cities has become increasingly evident, with a new global study revealing a significant rise in the number of warm nights over the past decade. The research, conducted by Climate Central and Climate Trends, analyzed data from approximately 300 Indian cities with populations exceeding 100,000. The findings show that, on average, these cities experienced a 32% increase in the number of nights with minimum temperatures reaching or exceeding 25 degrees Celsius between 2014 and 2023.
The study defines nights with temperatures of 25°C or above as unusually heated, noting that sleep quality is typically disturbed above this threshold. On average, Indian cities experienced 718 such nights during the study period. When the effects of climate change are removed from the calculations, this number drops to 543 nights, highlighting the substantial impact of global warming on nocturnal temperatures.
Geographically, the research indicates that cities in West Bengal and Assam have been most severely affected by this trend. Jalpaiguri, located in the Dooars region of northern West Bengal, tops the list of impacted cities, experiencing 868 nights with temperatures exceeding 25°C during the decade studied. Other significantly affected cities include Guwahati, Silchar, and Dibrugarh in Assam, as well as Siliguri in north Bengal. These cities have seen between 80 and 86 additional warm nights each year due to climate change.
The urban heat island effect is identified as a major contributor to the rise in night-time temperatures. Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology in Pune, explains that high-rise buildings and concrete structures in urban areas trap heat, preventing it from dissipating during the night. This phenomenon exacerbates the overall warming trend caused by climate change.
K J Ramesh, former director-general of the India Meteorological Department, corroborates the study's findings, stating that the trend is "hundred percent correct." He notes that cities in eastern and northeastern India are particularly affected by climate change, as evidenced by the heightened night-time temperatures. This observation aligns with the latest reports from the Intergovernmental Panel on Climate Change (IPCC).
The implications of this warming trend are far-reaching and concerning. Aarti Khosla, director of Climate Trends, warns that without significant reductions in fossil fuel consumption, some areas may experience night-time temperatures consistently above 25°C during hot weather by the end of the century. This scenario could lead to longer, hotter, and sleepless nights, particularly affecting vulnerable populations.
The study also reveals that climate change has added approximately 50 to 80 warm nights annually between 2018 and 2023 in cities across various Indian states, including Kerala, Karnataka, Maharashtra, Tamil Nadu, Punjab, Jammu and Kashmir, and Andhra Pradesh. Among major metropolitan areas, Mumbai has seen the most significant changes, with an additional 65 warmer nights per year attributed to global warming.
The health implications of this trend are significant. Dr. Arup Haldar, a sleep expert, explains that warmer temperatures make it more difficult for the body to lower its temperature for sleep onset, leading to difficulties in falling and staying asleep. This disruption in sleep patterns can have wide-reaching consequences for public health and productivity.
Anjal Prakash, a professor at the Indian School of Business and former IPCC author, emphasizes the disproportionate impact on poor and vulnerable sections of society who lack access to proper cooling mechanisms. The increasing number of warm nights poses a particular threat to these communities, potentially exacerbating existing social and economic inequalities.
The study also points to air pollution as a contributing factor to the warming trend. Increased pollution and cloud cover trap longwave radiation emitted by the Earth between the cloud base and the surface, further elevating temperatures. This highlights the complex interplay between various environmental factors in driving the observed changes in night-time temperatures.
As Indian cities continue to grapple with the effects of climate change, the findings of this study underscore the urgent need for comprehensive climate action and urban planning strategies. Addressing the root causes of global warming, improving urban design to mitigate heat island effects, and developing targeted interventions to protect vulnerable populations will be crucial in adapting to and mitigating the impacts of rising night-time temperatures.
