Record summer temperatures across Europe have been linked to a measurable drop in cognitive performance, researchers explain, raising concerns for workplaces, schools and health services already stretched by the climate crisis.

When the mercury climbs above 30 °C, the human brain, which accounts for just 2 % of body weight but consumes roughly 20 % of its energy, begins to overheat. Pieter Vancamp, a neurobiologist at the PhanLab research centre in Nantes, France, says the heart must work harder to pump blood to the skin for sweating, leaving less circulation for the brain. "When heat exceeds our capacity to sweat, the supply of blood to the brain might not be optimal anymore, and the brain starts to overheat," he told UnionPress.

Even a one‑degree rise can disrupt neural signalling. Vancamp notes that synapses become less efficient, producing nausea, anxiety and fatigue as the brain misinterprets the physiological stress. "The anxiety, the fatigue, you get it because your brain can't cope with the heat anymore and your brain cells communicate less well," he added.

These effects are not limited to the elderly or those with pre‑existing conditions. Mona Bielig, an environmental psychologist at the University of Konstanz, Germany, observes that healthy young adults also experience reduced attention and slower reasoning under extreme heat. "There is a rather broad temperature zone under which an average person can adapt. But at the edges, cognitive performance declines, especially on complex tasks which require a lot of attention," she explained.

Humidity, personal sensitivity, duration of exposure and access to cooling, such as air‑conditioned rooms or shaded outdoor spaces, shape the exact threshold at which performance drops. Studies cited by Bielig indicate that the decline becomes noticeable around 30 °C, while this summer many cities recorded sustained temperatures above 40 °C.

Heat stress also triggers a hormonal response. Elevated cortisol levels increase agitation and a false sense of alertness, compounding the difficulty of concentrating. Combined with poor sleep and dehydration, the result is a population that feels irritable, impulsive and less productive.

Implications for work and public services

Employers across the EU are reporting higher absenteeism and lower output during heat spikes. In sectors that rely on precision, such as manufacturing, logistics and healthcare, even minor lapses can have safety implications. Trade unions have begun calling for mandatory cooling breaks and the provision of drinking water in workplaces, arguing that current health‑and‑safety regulations do not adequately address climate‑induced risks.

Schools are facing similar challenges. Teachers in southern France and Spain have warned that students struggle to retain information during prolonged heat, prompting calls for adjusted timetables and investment in classroom ventilation. The European Commission's recent proposal on a "Heat‑Ready Europe" includes measures to improve building insulation and promote passive cooling, but critics say the plan lacks binding enforcement.

Long‑term adaptation versus mitigation

Both scientists stress that relying on human adaptation alone is unrealistic. "People make the mistake of thinking our bodies can adapt, and that we will get used to this heat by the next generation. Evolution takes much more time," Vancamp warned. He argues that the only viable path is to curb greenhouse‑gas emissions while retrofitting the built environment to withstand higher temperatures.

Practical steps include expanding green roofs, improving urban shading, and encouraging clothing designed for heat dissipation. Technology such as smart ventilation systems can also reduce indoor heat without excessive energy use, a point highlighted by the European Climate Foundation as essential for a just transition.

For now, the immediate reality is that many Europeans are feeling the cognitive toll of a warming climate. As the continent endures longer and more intense heatwaves, the pressure on workers, students and public services will only increase, underscoring the urgency of coordinated climate action and sensible adaptation policies.