Carbon Brief · Klimaat

Climate change exposes 580 million children to 20 extra ‘heat-stress days’ every year

A new study published in Science Advances reveals that over 40% of children globally under the age of 10 are already experiencing at least 20 additional "heat-stress days" annually due to climate change. The research combines climate models with demographic data to identify the most affected age groups and regions.

The study highlights that children under nine years old face more additional heat-stress days globally than any other age group. South Asia, Southeast Asia, and West Africa are identified as regions with the highest childhood exposure to dangerous levels of humid heat, largely due to rapidly growing populations with a significant proportion of young children. The paper warns that as the climate continues to warm, children will remain disproportionately exposed to heat stress.

High temperatures, especially when combined with humidity, can be deadly. The study defines a "heat-stress day" as any day with a wet-bulb globe temperature above 28C, a threshold for "moderate heat stress." Researchers simulated present-day climate patterns (1.3C warming due to human activity) and compared them to pre-industrial conditions to quantify "extra" or "attributable" heat-stress days caused by climate change.

Low-latitude countries, particularly in the tropics, record the most extra heat-stress days. For instance, Côte d’Ivoire faces 112 heat-stress days annually, with about half attributable to climate change, while Germany experiences only 0.1 such days on average. The study's lead author notes that the data does not capture the urban heat island effect, potentially underestimating local heat stress, especially in cities.

Extreme heat poses a greater risk to vulnerable populations, including children, the elderly, and individuals with pre-existing health conditions, due to their bodies' reduced ability to regulate temperature. Globally, 583 million children under 10 experience at least 20 attributable heat days yearly, representing 44% of this age group. In comparison, 190 million people aged 60-69 face at least 20 attributable heat days, making up 30% of their cohort.

Children face greater exposure to humid heat due to two primary factors: the larger global population of young people compared to older adults, and the higher proportion of young children in the rapidly growing populations of countries in Africa and Asia. Conversely, cooler northern hemisphere countries tend to have older populations.

The research also analyzed scenarios for a 1.5C and 2C warmer world, projecting increased exposure to heat stress. In a 1.5C warmer world, 13% of under-10s would experience 100 or more extra heat-stress days annually, rising to 23% in a 2C warmer world. For those aged 60-69, these figures increase from 9% to 17% respectively. The study emphasizes that higher warming levels expose more people to heat stress, with younger cohorts being the worst affected.

While the study's methodology is praised for its robustness and contribution to climate justice discussions, some experts suggest it might overstate the contrast between children and the elderly, potentially underestimating the vulnerability of older adults who may face social isolation and mobility issues. Additionally, populations in mid-latitudes, less adapted to heat, may experience stronger relative risks of heat mortality.

The study's findings are crucial for informing climate justice discussions, particularly concerning children in developing countries who have contributed the least to historical greenhouse gas emissions but are most severely impacted by increased heat-stress days. The research also helps fill data gaps in global reporting on heatwaves, which often underrepresents events in regions like Africa.

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