The dangers of extreme heat are well documented. The World Health Organisation has long warned that rising temperatures worsen existing health conditions, including cardiovascular disease, diabetes and asthma. But emerging research suggests the consequences of a warming planet may be broader and more insidious than previously understood.
This summer alone, heatwaves sweeping across Europe were linked to an estimated 24,400 deaths. Scientists calculate that without human-driven climate change, around 16,500 of those deaths could have been avoided, meaning global warming effectively tripled the toll.
Now, researchers from University of California Santa Barbara are warning that the impact of extreme weather extends far beyond immediate fatalities, with troubling implications for pregnancy and early childhood development.
Why humidity makes heat more dangerous
In a study published in Science Advances, scientists found that high humidity significantly worsens the effects of extreme heat. The reason is physiological: the human body cools itself through sweating, but when the air is humid, evaporation slows and heat builds up internally.
“All that heat accumulates in the body, leading to heat stress,” explained lead author Katie McMahon, noting that dangerous levels of heat stress can occur even at moderate temperatures if humidity is high.
Pregnant women are particularly vulnerable. Added body weight, hormonal changes and altered heat regulation make it harder for them to cool down, increasing the risk of overheating.
Pregnancy under heat stress
Heat stress during pregnancy can trigger premature labour, especially in the later stages. Babies born prematurely often face long-term health challenges, including impaired physical development that may be difficult to reverse.
“Extreme weather harms far more people than it kills,” McMahon noted, arguing that focusing solely on mortality figures obscures the broader health consequences of climate change.
Evidence of stunted growth in children
To assess the longer-term effects, researchers examined how children’s height compared to the average for their age, a standard indicator of chronic health in children under five.
The findings were stark. Children whose mothers were exposed to increased heat and humidity throughout all three trimesters of pregnancy were, on average, 13 per cent shorter for their age than expected. By contrast, exposure to extreme heat alone resulted in only a one per cent reduction.
The research focused on South Asia, a region scientists believe will be among the most severely affected by rising temperatures in the decades ahead.
A looming risk for millions
Under a high-emissions scenario projected for 2050, the study estimates that around 3.5 million children in South Asia alone could experience stunted growth as a result of combined heat and humidity exposure before birth.
Even if global efforts succeed in limiting warming to 2°C above pre-industrial levels, the authors warn that South Asia is still likely to endure deadly heat events every year.
The findings add to growing evidence that climate change is not only a future threat, but a present one, shaping health outcomes from the very earliest stages of life.
Source: Euronews