Firefighters in France are confronting a phenomenon never seen in the region before: fire clouds. It’s a sign of the intensity of the blazes burning—and how climate change is upping the odds that they appear.
A wave of fires has swept over France and Spain, sending hundreds of thousands fleeing. Firefighters on the frontlines are facing what a spokesperson for the French firefighter association told AFP called an “operational impossibility”—in other words, a “natural force beyond our control.”
As evidence of how out of control the wildfires in France are, look no further than the skies where the blazes have, in some cases, created their own weather. To form a fire cloud—what meteorologists call a pyrocumulonimbus or the even more metal-sounding cumulonimbus flammagenitus—you first need heat, which fires have in spades.
But just as important are dry conditions near the ground and cool, relatively moist conditions aloft in the atmosphere. As superheated smoke rises miles above the flames and into the cool atmosphere, water vapor condenses around the particles of ash to form water droplets. (Yes water vapor and water droplets are two different things.) As the air keeps rising, those water droplets eventually become ice crystals.
At this point, the smoke and water droplets have created a cloud, but unfortunately one that’s unlikely to provide much relief in the form of rain. Instead, these towering fire clouds can unleash lightning strikes that can start more fires and generate powerful downdrafts that reach the ground to fan flames further. At their worst, pyrocumulonimbus clouds can even spawn tornadoes.
Pyrocumulonimbus clouds have been documented in the US, Canada, and Australia, among a handful of other locations. But until now, there were no documented fire clouds in France. While the country is no stranger to wildfires, the size and ferocity of this summer’s blazes is well outside the normal.
Last week was France’s single most destructive week for wildfires over the past 20 years, according to data from the European Forest Fire Information System. It more than doubled the previous record during that period, which coincides with accurate satellite data. This isn’t an isolated bad week either. More than 220,000 acres have burned across the country so far, six times the annual average. That’s 61,000 acres higher than the previous yearly record.
If that sounds like a familiar trend, well, it unfortunately is. Burning fossil fuels has heated the planet up, making explosive wildfires more common and destructive around the world. A 2024 study found the incidence of extreme fires globally more than doubled from 2003 to 2023. Six of the seven most extreme years have happened since 2016.
After a slight weekend reprieve as temperatures dipped, they’re expected to rocket back up above 104 degrees Fahrenheit (40 degrees Celsius) in France and 108 degrees Fahrenheit in Spain later this week. That means firefighters will have to contend with more extreme fire weather—including the possibility of clouds created by the blazes themselves.
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