Discover more about pyrocumulonimbus – or fire clouds – and how climate change is making them more widespread
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More than 300,000 people across both Spain and France have been ordered to evacuate after wildfires ravaged the nations in recent days. Spain has declared a national emergency, while authorities in Bordeaux have warned the wildfire there may continue to burn for several months.
As thousands of people continue to evacuate, experts warn that ‘fire clouds’ are making these blazes more intense.
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What are fire clouds?
Essentially, pyrocumulonimbus – or fire clouds – are gigantic storm clouds created by a wildfire.
Dubbed as ‘fire-breathing dragons’ by NASA, these clouds are first created as wildfires generate heat, causing the air to rise above the blaze and smoke, ash and water vapour into the atmosphere. Once air rises, it cools, and water vapour condenses into clouds.
Powerful and intense fires can create fire clouds, which can reach altitudes of 10–15 kilometres (six to nine miles). Such clouds are more likely when there are dangerous conditions like high temperatures, little moisture and strong winds.
Fire clouds can make wildfires more unpredictable and dangerous. They can generate their own lightning, triggering further fires away from the initial impact zone, as well as causing strong winds to spread wildfires even faster.
‘In some cases, pyrocumulonimbus events can inject smoke into the upper troposphere or even the lower stratosphere, reaching altitudes comparable to those associated with a moderate volcanic eruption,’ said fire forecast coordinator at the European Centre for Medium-Range Weather Forecasts (ECMWF) Dr Francesca Di Giuseppe.
Sometimes, fire clouds can produce rain to help extinguish a fire.
Where do fire clouds happen?
Fire clouds were once rare events, but in recent years have become increasingly common. Take the example of the 2019 and 2020 Black Summer bushfires in Australia, which created extreme ‘firestorms’ that made their own weather. Fire clouds have also been reported in California throughout the summer of 2021, towering 1.6 kilometres (one mile) above the state.
They are becoming common thanks to climate change, which is creating intense conditions for wildfires to occur. According to the Royal Meteorological Society, fire clouds are likely to become more frequent as hotter and drier conditions increase the risk of wildfires.
However, this is the first time fire clouds have been spotted in France.
‘It’s the first time France has had to explicitly consider the concept of a pyroCb,’ says adjunct professor from the University of New South Wales’ bushfire research group Rick McRae. ‘Whether or not they had one a few days back or not isn’t really the question,’ he says, ‘the question is whether there’s one coming on Tuesday, Wednesday this week.’
