The dangers of warmer nights during Indian summers are often overlooked, but they pose a significant threat to public health, especially for those living in less affluent areas. While heatwaves and peak daytime temperatures dominate the conversation, the rising nighttime temperatures could be even more detrimental.
The human body relies on cooler evenings and nights to recover from the heat of the day. However, when nighttime temperatures remain high, the body's ability to recuperate is compromised, leading to prolonged and sustained exposure to heat. This is particularly concerning for individuals in low-income housing, where natural ventilation and access to air conditioning are limited.
A recent study conducted in Chennai revealed a disturbing trend. Occupants of medium and low-income residential units were found to be sleeping in temperatures exceeding 32° Celsius, with some nights even reaching 35° Celsius. This is a cause for alarm, as the health impacts of indoor heat exposure have not been extensively studied in India. Global studies suggest that nighttime warming is a significant contributor to heat-related deaths, and researchers are now quantifying these impacts in Indian contexts.
The rise in nighttime temperatures is a nationwide phenomenon, but it is more pronounced in urban areas due to the urban heat island effect. Concrete, roads, and metal absorb heat during the day and release it at night, exacerbated by a lack of vegetation, water bodies, and dense high-rise buildings. The increasing use of air conditioners, which emit hot air, further contributes to this effect, creating a significant temperature difference between city centers and their outskirts.
The implications of warmer nights are far-reaching. Sleep discomfort, restlessness, exhaustion, and a lack of energy directly impact people's productivity and overall well-being. Furthermore, the adverse health effects are substantial and still being assessed.
Dileep Mavalankar, a leading expert on heat and its health impacts in India, provides a compelling example. In Ahmedabad, where daily all-cause mortality records are maintained, a clear correlation between nighttime temperatures and mortality rates is evident. When the maximum nighttime temperature exceeds 30° Celsius, mortality rates skyrocket. This highlights the urgent need to address the rising nighttime temperatures and their impact on public health.
While heat action plans are in place across many states and cities, they primarily focus on heatwave situations, which are relatively rare events. Extreme heat, however, is a constant during Indian summers, and the trend of rising nighttime temperatures is only expected to worsen. It is crucial to prioritize long-term measures, such as improving urban infrastructure, developing better low-cost housing, and increasing green spaces, to mitigate the impacts of extreme heat.
In the interim, passive cooling solutions, such as reflective roof coatings and natural ventilation, can provide immediate relief to those living in cramped households. These measures, along with a greater emphasis on the heat action plan's long-term goals, are essential to tackling the challenges posed by warmer nights during Indian summers.
