PANAJI
India's monsoon season could become nearly as hazardous as the pre-monsoon summer for heat-related health risks as climate change drives a sharp rise in hot and humid conditions, according to a new study by researchers at the Indian Institute of Technology (IIT) Gandhinagar.
The study found that "uncompensable heat stress" (UHS), a condition in which the human body can no longer regulate its temperature because of a combination of high heat and humidity, is expanding rapidly across the country and is expected to worsen in the coming decades.
Using ERA5 reanalysis data, historical mortality records from the National Disaster Management Authority (NDMA) and the India Meteorological Department (IMD), along with multi-model climate projections, the researchers analysed changes in heat stress between 1979 and 2021.
Currently, around 8 per cent of India's land area experiences UHS during the summer months, while only about 1 per cent is affected during the monsoon. However, under a global warming scenario of 2°C above pre-industrial levels, monsoon-season UHS is projected to expand dramatically, affecting nearly 53 per cent of the country—almost matching the 60 per cent projected during the summer.
The researchers said that while India's heat-related health burden has traditionally been linked to the dry pre-monsoon months of March to June, humid monsoon conditions are likely to become equally dangerous as rising temperatures combine with increasing atmospheric moisture.
Unlike dry heat, high humidity limits the body's ability to cool itself through sweat evaporation, making prolonged exposure potentially life-threatening even for healthy individuals engaged in light physical activity.
The study also found that summer heat stress currently accounts for a larger share of heat-related deaths than monsoon conditions. However, the researchers cautioned that this trend could change as humid heat intensifies in a warming climate.
The Indo-Gangetic Plain, northwestern India and eastern coastal regions were identified as major hotspots, together home to more than 700 million people, including large numbers of outdoor workers and vulnerable communities.
The researchers argued that existing heat-risk assessments relying solely on air temperature or wet-bulb temperature may underestimate actual health risks. They recommended that future heat action plans and early warning systems incorporate both temperature and humidity thresholds to better protect people from rising heat stress throughout the year.
