As tens of thousands of people continue to be evacuated from parts of southern France ravaged by wildfires, firefighters are facing a new threat never seen before in the region in the form of “fire clouds”.
Described by Nasa as the “fire-breathing dragon of clouds”, pyrocumulonimbus formations are the result of extreme heatwaves and can lead to wildfires.
Sophie Brocas, the prefect of the Gironde in Bordeaux at the epicentre of recent blazes, told Le Monde the “incredible, unprecedented, unknown phenomenon” meant we are “entering a new dimension” when it comes to fighting the effects of global warming.
How are they formed?
Pyrocumulonimbus or cumulonimbus flammagenitus – more commonly known as fire clouds – are created by intense heat from the Earth’s surface. This is usually caused by volcanic eruptions or large wildfires where temperatures can reach as high as 800C.
The rapidly rising plume of air cools and forms fire clouds, which, when combined with enough moisture and strong updrafts, can develop into so-called “fire storms”. These produce downdrafts that spread burning embers and dry lightning that starts new fires; and they can even form dangerous fire tornadoes.
The result is so intense, they effectively create their own internal weather systems.
Are they getting more common?
Fire clouds have become increasingly common in the US, Canada and Australia, where the 2019-20 “black summer” bushfires killed at least 33 people and destroyed more than 11 million hectares (27.2 million acres) of bush, forest and parks.
Fire officials in New South Wales reported that embers from the fire storm were landing 18 miles ahead of the front, three times more than the usual distance, said the BBC. But until now, there have been no documented cases in France or northern Europe.
Given pyrocumulonimbus are more likely in extreme weather conditions such as high temperatures, strong winds and little moisture, scientists have warned climate change is likely to increase the chance of them forming.
How can they be stopped?
With the advent of devastating fire clouds, French authorities have “reached a point of ‘operational impossibility’ that requires us to accept the need for strategic retreat”, Lieutenant Colonel Eric Brocardi, spokesman for the National Firefighters Federation of France, told Agence France-Presse.
These fires are convective, which is a problem because they create their own winds “that constantly shift direction, unlike a standard fire that spreads in a conical pattern”. This makes the movement of the blaze “completely unpredictable” as it spreads outwards and becomes impossible to fight head-on.
“It’s a David-versus-Goliath scenario: the idea is that, at some point, we’ll find a weak spot and strike there”, said Brocardi.
“Salvation will come either from the sky – in the form of rain, though it would need to pour heavily for three days – or by finding a way to steer the fire towards a place where it will die out on its own. The sea, for example.”