A new research has revealed that climate change is risking the physical development of millions of children worldwide.
The groundbreaking study published in Science Advances has uncovered a dire link between extreme heat, humidity, and childhood stunting, a condition of impaired growth and development that can last a lifetime.
Led by researchers at UC Santa Barbara, the report warns that the cascading health impacts of a warming planet have been “severely underestimated,” extending far beyond immediate heat-related illnesses.
While the dangers of extreme heat are well-documented, such as the 24,400 heatwave deaths in Europe this summer, a toll tripled by human-caused climate change, this new analysis highlights a more insidious process. The critical factor isn’t temperature alone, but wet-bulb globe temperature (WBGT), a measure that accounts for humidity, radiant heat, and airflow.
“Humidity acts as a blanket, preventing our bodies from cooling through sweat evaporation,” explains lead author Katie McMahon. “All that heat builds up internally, causing physiological stress even at what might seem like manageable temperatures.”
This heat stress is particularly dangerous for pregnant women, whose bodies are already under strain. The study, drawing on vast child health data from the Demographic and Health Surveys (DHS), found that each additional day with a maximum WBGT exceeding 29°C correlated with fewer live births six to twelve months later. Heat exposure can trigger premature labor, disrupt nutrient absorption, and elevate disease burden, all pathways to stunting.
The research paints an alarming geographical picture. Even if global warming is limited to 2°C above pre-industrial levels, the upper target of the Paris Agreement, South Asia is projected to face deadly heat events annually. Regions with already high humidity, such as parts of Southeast Asia, sub-Saharan Africa, and coastal Latin America, will see WBGT reach critical levels more frequently.
Already, The World Health Organization estimates that 149 million children under five currently suffer from stunting globally, with long-term consequences for cognitive development, educational outcomes, and economic productivity. Climate change is now poised to exacerbate this crisis.
“This isn’t just a public health issue, it’s an agricultural, economic, and social protection emergency,” notes co-author Dr. Amir Jina of the University of Chicago. Heat stress reduces crop yields and nutrient density in staple foods, while also limiting caregivers’ ability to work and provide care. Children in subsistence farming communities face a double burden: reduced nutritional intake and increased physiological stress.
The study therefore calls for “integrated resilience strategies” that bridge sectors:
Health systems must develop early-warning systems for pregnant women and expand maternal cooling interventions.
Agriculture needs heat-resistant crops and shifted planting calendars.
Urban planning must prioritize green spaces and cooling centers.
Social protection should include heat-income support for vulnerable families.
“Reducing emissions remains paramount,” McMahon stresses, “but adaptation can no longer be an afterthought. We are already locked into decades of increasing heat. Protecting the next generation requires acting on this data today.”
As global temperatures continue to rise, the metric of success may no longer be just degrees Celsius, but centimeters of growth and the future potential of millions of children hanging in the balance.
