A study found that climate change is exposing about 560 million children under 10 worldwide to at least 30 days of additional heat stress each year. That is nearly three times as many people as those in their 60s who face the same level of additional heat stress.

The Verge reported on Aug. 26 that an international research team including Vrije Universiteit Brussel published a study in the journal Science Advances analysing how climate change affects heat exposure by age group. The researchers defined heat-stress days as those when the wet-bulb globe temperature, or WBGT, which reflects humidity and wind speed as well as air temperature, exceeds 28 degrees Celsius in the shade. At that level, protective measures such as reducing activity or resting are recommended to prevent heat-related illness.

The analysis found that up to 560 million children aged 0 to 9, or 43 percent of that age group, experience 30 or more additional heat-stress days a year due to human-caused climate change. That is nearly three times the roughly 190 million people aged 60 to 69 exposed to the same conditions. The study defined a month as a yearly total of 30 days or more and said it does not necessarily mean a continuous period.

The impact was concentrated in tropical and low-income regions such as South Asia, Southeast Asia and West Africa. These regions have historically contributed relatively less to greenhouse gas emissions, but have younger populations and lower access to cooling and to health and housing infrastructure, which can increase harm to children.

The burden is expected to grow if warming continues. The study estimated that if the global average temperature rises 1.5 degrees C above pre-industrial levels, 620 million children would experience an additional month of heat stress, rising to 650 million at 2 degrees C.

Children are less able to regulate body temperature than adults. Their smaller bodies can overheat quickly, and infants and young children have sweat glands that are still developing, making them more vulnerable to dehydration and heatstroke. The researchers stressed that greenhouse gas cuts are needed alongside expanded access to cooling, heatwave response plans and stronger health systems.