In many countries in the Northern Hemisphere, school reopens in early autumn—a time that is supposed to offer a welcome break from the intense summer heat. In recent years, autumn heatwaves have increasingly disrupted the expectation for cooler, more comfortable weather for the return to school, which have increasingly disrupted school activities and heightened children's heat exposure risks.

In a study published in Weather and Climate Extremes, Prof. QIAN Cheng’s group at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, along with collaborators from China, the US, and the UK, focused on the exceptional autumn heatwave that struck China from 1-10 September, 2024, and conducted an attribution and projection analysis using a refined storyline-probability combined framework.

“We found that human-caused climate change has already increased the frequency of such autumn heatwaves by more than 500 times and intensified them by more than 2°C under current climate,” said Prof. QIAN. “Even if we achieve the Paris Agreement’s 2°C target, near the end of this century children will still face heatwaves that are five times more frequent and nearly 1°C hotter than today—turning what should be a cool, comfortable return to school into a serious health hazard.”

Researchers explained what "children's exposure to heatwaves" means from a public health perspective. Children are more vulnerable than adults during extreme heat. Their bodies are less efficient at regulating temperature, and they often rely on adults to keep them cool and hydrated.

When a heatwave strikes during school hours, children may be exposed to dangerous levels of heat in classrooms without air conditioning, on playgrounds, or during commutes, which can lead to heat exhaustion, heatstroke, dehydration, and longer-term impacts on learning and development. Exposure risk is the combination of how hot it gets and how many children are in harm’s way.

Moreover, researchers found that human-caused climate change has increased children’s exposure risk to 2024-like heatwaves by about 55% under current climate and population levels, and this trend will become more complex. Under a high-emission scenario, children’s exposure risk will initially decline due to a rapidly decreasing child population, but the trend will be reversed by the sharply increasing intensity of heatwaves toward the end of the century. Only under lower-emission scenarios (SSP1-2.6, aligned with the Paris Agreement) does the exposure risk will continue to fall.

The findings of this study highlight the urgent need for both emission reductions and child-focused adaptation strategies such as heat-resilient school buildings, flexible school calendars, and heat-health action plans.