In an unprecedented move, France has ordered the closure of schools across half of its territory as a relentless heatwave, now in its third week, pushed temperatures above 40°C in many regions. The red alert, the highest level of the national warning system, has been declared for 50 of France's 101 departments, stretching from the Atlantic coast to the Rhone Valley. This event marks the most extensive red alert since the system was established in 2004.
The heatwave, which meteorologists have attributed to a persistent omega block pattern in the upper atmosphere, is consistent with the predictions of climate models for a world that has warmed by 1.2°C above pre-industrial levels. The physical mechanism is straightforward: a high-pressure system acts as a lid, trapping heat and preventing convection. As the ground and air warm, the heat cap strengthens, creating a feedback loop that can last for weeks. The result is not just high daytime temperatures but dangerously warm nights, as the urban heat island effect prevents cities from cooling down.
The health implications are severe. France's health authority reported a 30% increase in emergency room visits for heat-related illnesses compared to the same period last year. Among the most vulnerable are the elderly and those with chronic conditions. The closure of schools is a pragmatic step to reduce exposure for children, who are physiologically less efficient at regulating body temperature. But it also disrupts routines and places additional strain on working parents.
The energy sector is under parallel stress. The heatwave has reduced the output of nuclear power plants, which rely on river water for cooling. Several reactors along the Rhone have been forced to reduce capacity as river temperatures rise, limiting their ability to dissipate waste heat. This comes at a time when demand for air conditioning is surging, pushing the electricity grid to its limits. France, typically an electricity exporter, may be forced to import from neighbours.
Beyond the immediate crisis, this event underscores a longer-term trend. A study by the French meteorological service indicates that such extreme heat events are occurring more frequently and intensifying. The 2003 heatwave, which caused over 15,000 deaths in France, was considered a once-in-a-century event. Today, such events are expected every 10 to 20 years under current warming trajectories. Without significant mitigation, by 2050, much of France could experience temperatures exceeding 45°C every other year.
The French government has activated its inter-ministerial crisis unit and established cooling centres in major cities. But these are stopgap measures. The fundamental challenge is to adapt infrastructure and society to a climate that no longer resembles the one in which they were built. Urban planning, building codes, and public health systems must be retrofitted for a warmer world. And of course, the root cause emissions of greenhouse gases from fossil fuels must be addressed.
As I file this report from London, where thermometers are also flirting with record highs, the message from France is clear. The planet is warming and the consequences are no longer abstract. They are here, disrupting daily life and demanding a response that matches the scale of the problem. The science is settled on what causes these heatwaves. The question is whether our political and social systems can act with the same urgency as the atmosphere.