Climate change heat stress puts 145 m Indian children at risk of dehydration, heatstroke: Study

Kandhari, who has set up Warrior Moms, a nationwide network of mothers and citizens fighting for children’s right to breathe clean air, is now seeing another threat converge with air pollution: extreme heat. Her concerns resonate with new research from Vrije Universiteit Brussel (VUB), which finds that up to 560 million children aged 0-9 globally — 43% of all children in this age group — are experiencing at least one additional month, or 30 or more days, of heat stress every year because of human-induced climate change. In India, the number is 145 million children, or 61% of those aged 0-9.

The study, published in Science Advances, combined population data with state-of-the-art climate models and attribution science to determine how much of this exposure can be linked specifically to human-induced climate change.

According to Rosa Pietroiusti, lead author of the study and a PhD researcher at VUB, children’s exposure is higher than that of any other age group. It is also nearly three times the number of people aged 60-69 — about 190 million, or 30% of that age group — experiencing at least one additional month of heat stress.

Why are the findings significant?

The findings are particularly concerning because children are physiologically more vulnerable to extreme heat. Their bodies heat up faster than those of adults, they sweat less efficiently and they depend on adults to keep them hydrated, rested and protected. Excessive heat can disrupt the body’s normal functioning and, in severe cases, cause dehydration, heatstroke and organ failure. It can also interfere with learning and cognitive development.

The study focuses on humid heat, which can be more dangerous than dry heat because high humidity prevents sweat from evaporating efficiently, making it harder for the body to cool itself. As climate change makes heat waves more frequent and intense, children are increasingly exposed to conditions in which their bodies struggle to regulate temperature.

The risks are not evenly distributed. Children from low-income families can be particularly vulnerable because they may have fewer options to escape the heat — whether through air-conditioning, reliable electricity, access to cool spaces or the ability to alter school and travel routines.

Dr Harshal Salve of AIIMS, New Delhi, said the research adds to the growing evidence of the health impacts of climate change on children. “UNICEF has warned that nearly half of the world’s children face at least three major climate-related threats, including extreme heat and heat waves. In India, rising temperatures and more frequent heat waves are making it increasingly difficult for children to stay safe and healthy. Children from low-income families are at even greater risk because they often have fewer ways to protect themselves from the heat. When children’s health suffers, it can affect their education, growth and, ultimately, our future,” he added.

What does heat stress mean?

Heat stress days in the study are days of humid heat stress, defined as a wet-bulb globe temperature in the shade of more than 28°C. At these levels, protective measures such as reducing physical activity and taking structured rest periods are recommended to prevent heat-related illness.

Additional heat stress days are those attributable to human-induced climate change — days that would not have occurred in the absence of climate change. Researchers estimate these using attribution methods applied to observation-based reanalysis data or global climate models. Total heat stress days include both days attributable to climate change and those that would have occurred even without it.

Heat burden is rising in India

The VUB analysis shows that climate change has already doubled the number of Indian children aged 0-9 exposed to at least five total months of dangerous heat stress each year — from 59 million to 118 million, or 50% of children in this age group.

The projections become starker with further warming. In a 1.5°C warmer world, around 166 million Indian children (74%) aged 0-9 are projected to experience at least one additional month of heat stress each year. Around 123 million (55%) could experience at least five total months, or 150 days, of heat stress.

In a 2°C warmer world, the number experiencing at least one additional month of heat stress could rise to 169 million (96%), while around 120 million (68%) could experience at least five total months.

Globally, the pattern is similar. In a 1.5°C world, around 620 million children (49%) aged 0-9 are projected to experience at least one additional month of heat stress per year. At 2°C of warming, this could rise to around 650 million (59%). South Asia, Southeast Asia and West Africa are projected to have the highest numbers of children exposed to dangerous heat stress.

For Wim Thiery, senior author of the study and professor at VUB, the findings underline the need for urgent action. Protecting children from the worst impacts of climate change will require policymakers to drastically reduce fossil-fuel emissions and limit warming in line with the Paris Agreement.