It was on New Year's Eve 2019, with the horror summer not yet done and a global pandemic still to come, that Greg Mullins saw something once thought to be fire-fighting legend: a blaze so big it generated its own lightning storm.

As a kid, watching his father rush off to fight fires and then signing up himself to his local brigade at 13, he’d heard the stories of such phenomena. “But none of us expected to see one.”

On the last night of 2019, when the storm front came, it blocked out the sun, throwing down spears of lightning that ignited new fires as the inferno spread in every direction and tore through homes on the South Coast.

“You could hear the thunder,” says Mullins, an ex-fire commissioner of NSW. “The fire was racing across people’s front lawns. Even the kangaroos couldn’t escape. I just felt totally powerless.”

Up until 2019, there had only been about 60 fire-generated storms confirmed or suspected in Australia. Then in just one fire season, our devastating Black Summer, that number nearly doubled. In the United States, the meteorologist who first discovered the phenomenon Mike Fromm says the smoke reached higher into space than ever before, as high as a nuclear blast. A firefighter was killed when a fire tornado or large “fire whirl” flipped an eight-tonne tanker. “It’s the biggest outbreak of firestorms we’ve seen,” Fromm says.

Bushfires aren’t just getting bigger and more frequent in Australia, the continent of fire. They’re getting stranger. Moving faster, flaring unpredictably, changing the weather. While once “good fire” helped rejuvenate the landscape under the careful watch of its First Nations, today global warming is fanning flames too big to live with.

During Australia’s deadliest bushfire disaster, Black Saturday, nightmarish weather conditions came together in Victoria one February day in 2009. The fires moved fast, trapping people in cars and homes, and burning with the power of 1500 atomic bombs. By the time the 2019-20 Black Summer arrived, drought had turned much of the country into a tinderbox, and the flames didn’t seem to end, roaring for months, sometimes in every state. Tallying up the devastation, a recent royal commission warned “what was unprecedented is now our future”.

And we are not alone. Fire seasons around the world are stretching out, overlapping, intensifying. Places that have never burned before, such as the Arctic circle and parts of the Amazon, are going up. Even during a wetter La Nina season this year for Australia, Perth and Fraser Island have burned.

So what causes bushfires and how is global warming changing their behaviour on the ground? Are humans creating the fire equivalent of an Ice Age? And what can we do about it?

What is fire?

Of all the ancient elements, fire is unique – a chemical reaction not a substance. “It’s a shapeshifter and it takes its character from its context,” says the world’s leading fire historian, Stephen Pyne.

Three things must converge for fire. There must be an ignition; there must be oxygen to react; and there must be fuel to burn. Our planet is intrinsically flammable, full of gas and heat and foliage. Wildfires have raged for as long as plants have grown. The earliest were traced back through fossilised charcoal 420 million years ago, not long after vegetation first sprang to life on Earth.

In the deep past of prehistoric time, fire frequency was shaped by changes in oxygen levels. Lightning strikes and, occasionally, something more exotic such as sparks from an erupting volcano set fire to the land. The dinosaurs weathered megablazes of their own during apocalyptic extinction events.

Today, certain raptors in Australia, known as “firehawks” to local Aboriginal people, will sometimes take burning sticks from a bushfire to light others and so set a trap for their prey. The Bombardier beetle mixes a unique chemical cocktail in its abdomen to fire explosives from its backside (complete with smoke).

“But humans use fire like no other [species],” Pyne says. “It’s our ecological signature.”

And, as the Earth’s atmosphere has evolved and stabilised, humans have become the main drivers of fire. For hundreds of thousands of years, we have used it to survive the cold, to grow food and to stave off the ruin of large blazes by starting smaller, cooler burns. Some experts theorise it was at the hearth – the cooking fires around which our ancient ancestors gathered – that language emerged.

At the front of a wildfire, known as “the dead man’s zone”, temperatures can reach up to 800 degrees. The smoke is choking; it stings the eye. The inferno will roar like a freight train. Sometimes, there will be little booms in the distance as gas bottles explode or trees crash to the ground.

To put out a fire, you need to smother it or starve it. Water, dirt, certain chemicals, even blankets can choke it of oxygen. A grass fire might burn fast but then blaze out as it runs out of fuel. But the wind can make an inferno turn suddenly, or flare back to life. You can fight fire with fire, too – say, by backburning before an advancing blaze or running pre-emptive traditional burns to clear out underbrush.

But in the modern world, as Indigenous peoples have been pushed further from the map by colonisation, the old, traditional ways of managing the land with fire, as “medicine”, have all but disappeared.

Instead, Pyne says, we have industrialised fire; sent it sparking through wires as electricity to power our lifestyles, digging up and burning the fossilised landscape (coal, oil and gas) and in turn sending up a new kind of planet-warming smoke into the air. We don’t see fire as much any more, Pyne says – our homes are rarely lit by candlelight – and yet, thanks to electricity, it is more a part of the world than ever, burning day and night, wet or dry.

There are tales of great fires throughout history, of course. The Roman philosopher Lucretius described a blaze in the Pyrenees that burned so hot it melted ore. During the Portuguese colonisation of the island of Madeira in the 15th century, a fire is said to have burned for seven years, driving invaders back to the sea. Both stories are questionable, says Pyne, but no doubt born from impressive infernos.

Pyne warns that a new age of fire driven by humans is eating the last remnants of the old Ice Age.

Still, Pyne, who describes “smoke-chasing” and “hotspotting” in the Grand Canyon where he spent 15 seasons fighting fires himself, says something was different about Australia's Black Summer. And he can find no historical precedent for California’s own recent record-breaking fire season either. “We’ve had big fires like this before, but not four years in a row and not all burning at the same time,” he says.

Elsewhere around the world in Siberia, Greece, Britain, wildfires are also flaring up hotter and more often.

Pyne warns that a new age of fire driven by humans is eating the last remnants of the old Ice Age, the Pleistocene. “I call it the Pyrocene now,” he says. “The glaciers and forests are disappearing, megafauna are going, one by one, particularly those that live on ice like the polar bear.”

David Bowman, an ecologist pioneering the new field of “pyrogeography” at the University of Tasmania, agrees today’s megafires are perhaps the most visceral warning sign yet of global warming.

“They’re the [land] equivalent of an ice sheet breaking apart.”

How are fire seasons changing?

Rachael Cavanagh knows what good fire is. Her people – the Minyungbal and Yugambeh nations – have been wielding it, walking with it and watching it change and rejuvenate the landscape for millennia. But, as a career firefighter in northern NSW, Cavanagh was also on the front line of the Black Summer. In Coffs Harbour, crews were already exhausted from a long winter fighting fires by the time cities such as Sydney and Canberra were being engulfed by smoke, and communities down south evacuated from beaches.

“We knew it would be bad but it just didn’t stop,” Cavanagh says. “Forest would burn and two weeks later we’d be in there again fighting another fire. It was strange, surreal.”

In total, more than 24 million acres, an area bigger than England, burned across Australia. Thirty-three people were killed in the fires and hundreds more died from complications linked to smoke inhalation as the ash cloud spread across the country. For wildlife, it was the single biggest catastrophe in recorded history – 3 billion creatures were killed or displaced, and their ecosystems were decimated. Even ancient rainforest burned.

At the Bushfire and Natural Hazards Co-operative Research Centre, which is now working to update Australia’s existing McArthur forest fire danger index, chief executive Richard Thornton says the sheer size and duration of the fires left few places for animals to seek refuge. Now, in some forests struggling to recover, invasive weeds are thriving.In others, the very seeds cooked in the soil, interrupting the usual life cycle of plants adapted to fire.

Despite fake news about an “arson emergency”, almost all of the fires were started by lightning. In late October 2019, the mammoth storm that erupted over NSW unleashed more than 19,000 bolts, one of which ignited Australia’s largest megafire: the Gospers Mountain fire.

But Australia was not weathering a sudden epidemic of lightning strikes. Instead, as the climate warms, more violent storms and drier and hotter conditions on the ground are coming together to make bigger bushfires. Australia’s driest and hottest year on record was 2019. The Bureau of Meteorology even had to introduce a new colour code to capture some of the extreme temperatures seen across the country. When the season began, some towns had already run out of water to drink, let alone fight fires. And the deadly Black Saturday still holds the record for Melbourne's hottest day at 46.4 degrees.

Tom Beer was the first scientist in the world to link climate change to increased bushfires, in 1988. Back then, he was considering scenarios far into the future, when the amount of carbon dioxide in the atmosphere might be double what it was at the time. While emissions have ramped up even faster than predicted, Australia is only halfway (1.4 degrees) into the 3 degrees of warming Beer was modelling. But the fires are burning as if we are already there.

“In fact, they’re even worse,” Beer says. “Back then, we thought every year’s danger would be as bad as Ash Wednesday [in 1983]. We couldn’t really imagine anything worse. Now they’re bigger, they’re more dangerous, and the time between these horrors is shrinking down, from decades to years.”

Twenty years later, in 2008, Ross Garnaut built on the work of Beer and the CSIRO when he made the haunting prediction that hellish fire seasons would be “directly observable by 2020”.

Mullins says the seasons are getting more expensive and more exhausting to fight, running so long the window is narrowing for agencies to safely burn off vegetation through hazard reduction and overlapping with fires on the far side of the world, which strains resources. "You don't even need a [warm] El Nino event to get a bad season now either," he says. "Imagine if we’d had an El Nino last year, too."

How is fire behaviour changing on the ground?

Pyne likens fire to a driverless car, barrelling down the road. “At some point, there’ll be a sharp curve called climate change or a tricky intersection where town and country come together, or a lot of hazards leftover from land clearing,” he says. These changed conditions on the road mean changing fire behaviour.

Most homes are lost in ember attacks, sparks spitting ahead of a bushfire that come in like a locust storm, he says. Such spot fires were once common a few hundred metres ahead of a blaze. “Now we’re recording them 12 kilometres ahead,” Mullins says. "During Black Saturday too, people saw a smoke column about 20, 30 kilometres away. The next minute their house was on fire.”

For all the recent focus on fuel loads in Australia, fire scientist Jason Sharples says it actually makes little difference in extreme conditions. “That’s when usual fire behaviour goes out the window and it’s being driven by mass spotting. Hazard reduction isn’t going to stop that,” he says.

Take the catastrophic firestorm that ripped through Canberra in 2003, the one that showed Australia how strange fire could be. The flames came down from the mountains into the suburbs across bare paddocks, little more than dirt. “A fire like that will come in until it finds something to burn,” Sharples says.

“A strong wind kept roaring through the bush … Nothing human beings can do to stop a fire like that.”

Bushfires generally move faster uphill – heat rises, after all – but California is one of the few places where they can burn faster downhill, thanks to its famous northerly Santa Ana winds.

Sometimes, in a phenomenon known as “lateral spread” observed during Australia’s Black Summer as well as Black Saturday, fire will even run perpendicular to the wind. “It starts to create its own conditions,” Sharples says. “It usually only lasts a few hundred metres, and on rugged, dry terrain.”

But it can lead to “deep flaming”, or what Mike Fromm calls “mass ignition” when many embers are thrown out at once. “All of a sudden, a whole area can light up,” Fromm says. “In Canberra 2003, you saw the hillside exploding in a flash. It’s like a mini-version of a bomb going off.”

During the Black Summer, one of the biggest shocks came at night when the fires seemed to burn just as ferociously as they did during the heat of the day. Mullins recalls battling 30 metre-tall flames at 1am. “A strong wind kept roaring through the bush … Nothing human beings can do to stop a fire like that.”

What are firestorms and are they increasing?

Twenty years ago, when Fromm was called in to investigate mysterious clouds showing up on satellite feeds over the US, he saw in the data what firefighters on the ground had long called "the monster". These clouds weren’t ash from a volcano. They were coming from forest fires.

“It kind of broke the rules of what a thunderstorm should be able to do,” Fromm says now of his discovery, that "fire-breathing dragon" known as the pyrocumulus firestorm. “[They] act in many ways like a volcano, injecting stuff that comes off the fire into the stratosphere.”

Winds inside them can reach cyclone speeds. Sharples and his colleagues were the first to confirm a genuine fire tornado when they measured the path of the 2003 Canberra firestorm (at least an F2 tornado).

“These [storms] can have the worst behaviours,” Fromm says. “Thunder, hail, lightning … tornadoes. They’re the least predictable, the most dangerous [for] firefighters. But it’s odd. Typically, the bigger the thunderstorm the heavier the rain. With pyrostorms, it’s the opposite. They have a bigger boost to their updrafts but produce almost no rain. Just a lot of smoke.”

Enough to turn day to night.

So, how big does a fire need to be to create its own weather? Fromm says there’s no clear-cut size or temperature but it needs to cover “a very large piece of real estate” and burn “as hot as a fire can be so it generates that thermal bubble that starts the storm”.

It’s likely scientists are detecting more firestorms now because they know what to look for, but Sharples says fires are also burning bigger because of climate change and that’s setting the stage for wilder fire weather.

“You could smell the smoke flooding the cockpit at 34,000 feet. It’s like a big chimney.”

Filming inside the eye of a pyrostorm, that swirling vortex of smoke and ice crystals and forest debris, is still the “holy grail” for Fromm and other firestorm chasers. “We don’t quite do a Twister thing where we get a hunch and throw something into the storm,” Fromm says. But he has been on planes flown by NASA through suspected pyrostorm plumes to take measurements. “You could smell the smoke flooding the cockpit at 34,000 feet. It’s like a big chimney.”

After the atomic bomb was dropped on Hiroshima at the end of World War II, scientists think the mushroom cloud that formed was caused by firestorms from the infernos it ignited, rather than the initial bomb blast itself.

Some now wonder if the plumes from firestorms may be growing so big that they begin to affect the climate themselves, blocking light and even slightly cooling the atmosphere for months at a time, as major volcanic eruptions have in the past. The nuclear winter scenario.

“There’s a lot we don’t know about what [fires] do to the atmosphere, and that we can’t predict on the ground, whatever the models say,” says Bowman. “This thing fire has more tricks up its sleeve.”

How do we live with the fires of the future?

The Black Summer didn’t have to happen, at least not the way it did, says Cavanagh. "When our old people used to walk country and swim and do all the care they do, they put fire in as they went, the right fire at the right time to clear out grasses … or help [echidnas] forage … [We've] been fighting since colonisation to manage country again. So when fire comes in, it’s not the big one that rages because nothing’s burnt in 30 years.”

Unlike the walls of flame put in during a hazard reduction burn, Indigenous burns are lit in spiral, mosaic patterns, with room for animals to escape. They don’t roar into the treetops, they are not set when birds are nesting or bees are pollinating, when the winds are too strong. “You can walk in behind that fire and you should be able to brush the ash off the top of the soil and it will still be cool,” Cavanagh says. “Only the outer bark of the trees will burn.”

Unlocking the ecological puzzle of how Aboriginal people managed such a flammable landscape for so long could be key to Australia's future in a more fire-prone world, Bowman says. While more training and investment is needed, Cavanagh stresses the knowledge is not lost. “Often our women hold the fire lore and the medicine and they teach it to the children. My eight-year-old can read Country. She knows when to burn.”

“We now know we made the wrong choice. In some areas, they’re trying to put the good fire back in but it’s not easy.”

Up north, where Aboriginal communities have more land rights, cultural burns have been integrated into the forestry service for some time. Down south, it’s more fragmented. Crucial windows to burn often get missed under the slow grind of bureaucracy, Cavanagh says. Some agencies won’t pay local nations for their work, or let them burn on government land in the first place. And, while the Black Summer has sparked serious talk of scaling up the practice, Indigenous leaders stress burns must be led by local Aboriginal people, not merely tacked on to existing agency regimes.

After the “Big Blowup” inferno of 1910 that burned across the west of the US, some experts there advocated for reintroducing the traditional, cool burns of Native American tribes. Instead, agencies pivoted to a hardline “suppression” approach, the way fires are put out in cities. “No matter where the fire started, they wanted it out by 10am the next morning,” Pyne says. “We now know we made the wrong choice. In some areas, they’re trying to put the good fire back in but it’s not easy.”

Sharples, a Bundajlung man, says traditional burning might itself need to adapt to a warming climate and evolved terrain. But, if done right, he says it could be Australia’s best chance against worsening fire seasons. “These fires can be put out years before they actually start. Of course, it's not all we have to do."

Bushfire season is often followed by inquiry season in Australia, by soul-searching and reflection but usually, experts say, little practical action. The exception, Pyne says, was Black Saturday, which seemed to hit the Australian psyche "almost like a terrorist attack" and prompted an overhaul of community warnings. "Now [the Black] Summer is the same."

In its wake, Prime Minister Scott Morrison spoke of adapting to our worsening conditions, but the 2020 royal commission directly named the elephant in the room it saw as needing policy attention: climate change.

Mullins heads up a group of retired, senior-ranking firefighters calling on Australia to lead a rapid shift to a zero emissions economy. “We can say what the current [emergency services agency] commissioners can’t,” he says. “COVID has shown the government knows how to listen to scientists. Well, this is an emergency, too, and we can stop it getting worse.”

More bushfires also means more carbon released into the atmosphere, a wicked feedback loop. If the Black Summer fires were their own country, they would have been one of the world’s top emitters.

“If we’re not careful, this could end with us losing control entirely,” Bowman says. “Still, it’s not just about finding the right policy setting on decarbonisation. The fires are already here.”

Despite the US experience, Pyne says some remote fires may still need to be put out fast – that’s where drones and other technologies can help spot them early. The Morrison government says it will work to improve information sharing, including from satellites, but has largely ignored calls from firefighters – and now the royal commission – for more investment in large water-bombing aircraft.

“Under extreme conditions, if we leave fires burning far out and they get legs, an ember storm can blow them in anyway,” Sharples says.

So Bowman says communities must be better prepared for when fires do come close. He fears bush cities such as Canberra and Hobart could be primed for another fire storm in the coming years. “We’ve got too much [urban sprawl] pushing into forest. We’ve got the wrong houses in the wrong places.“

Ninety-nine per cent of the homes lost in the Black Summer were within 500 metres of fire-prone land, according to the Insurance Council of Australia.

Experts agree we need to get smarter about clearing fuels close to properties. But Mullins warns against kneejerk reactions – NSW’s new plan to allow landowners to clear bush within 25 metres of their fence line without environmental approvals was not recommended by a recent state inquiry and could threaten surviving koala populations. Deforestation has largely got the world into this mess, Mullins says. “We’ve changed rainfall patterns by chopping down rainforest and with so many species in trouble [after the fires], we have to be more careful than ever.”

“No one has [solved] this problem yet. We can’t look to a Sweden. But we are so much on the front line. Australia could be driving this.”

Building to fire codes is also expensive, often a big ask for communities already hit hard by fires. According to Sharples, even Australia's fire standard is designed to deal with the usual predictable blaze and not the fire of extremes. “There’s a little about embers but it’s mostly measured by radiant heat near the house.”

Bowman likens the change needed in Australia to the incremental road safety reforms under which everything from seatbelts to mandatory insurance became standard. “We need everyone on board, private industry as well as government – only, this has to be taken at a sprint. We’ve pressed the climate-change stopwatch now.”

The heroes in the story may well be local councils, he says, rallying and educating their communities. Or the change may be driven by the insurance industry: soaring premiums have already begun to price people out of wildfire-prone areas in the US.

“No one has [solved] this problem yet. We can’t look to a Sweden. But we are so much on the front line. Australia could be driving this.”

In the chaos of the pandemic, Pyne has been thinking more and more of fire as a virus – not living itself but feeding on what is. “Clearing out defensible space around our homes then becomes like social distancing,” he says. “Building fire-resistant houses is like wearing a mask; lighting good fires to stave off bad ones is building up herd immunity in the landscape. But there’s no vaccine for bushfires.”

At best, Bowman says: “It’s a negotiated truce.”