Virginia Young knew the fires were coming. As an Australian forest expert, she had contributed to research predicting longer and more-severe bush-fire seasons as the world warms.

But even she was taken aback by the sheer scale of the blazes that have imperiled much of the country — including her own home.

Now she worries Australia is on the brink of a “major ecological shift.” Climate change has pushed natural phenomena, such as wildfires, to mutate into more disastrous and deadly versions of themselves.

Temperatures are soaring to heights scientists did not expect to see for decades. Landscapes that are usually resistant to fire — including rainforests home to rare, vulnerable species — are going up in flames.

The blazes are so big they generate their own hellish weather.

Fire tornadoes, formed when spinning winds generate a massive rotating column of fire, ash, vapor and debris, are impossible to control. A volunteer firefighter in New South Wales was killed on Dec. 30 when one of these twisters overturned his truck.

“Ember attacks” occur when violent winds around wildfires pick up burning pieces of debris and carry them aloft, dropping them in a flammable spot where they start another blaze.

Fire whirls — short-lived swirling vortices of ash, dust and flame that are generated when updrafts of hot air become twisted as they rise along the leading edge of a forest fire, have been reported by witnesses. These whirls behave unpredictably — so much so they are sometimes called “devils” — and they can contribute to ember attacks, said Janice Coen, a project scientist at the National Center for Atmospheric Research in Colorado.

The heat from Australia’s blazes has fueled fire-generated thunderstorms from what are known as pyrocumulonimbus clouds. These mushroom-shaped clouds act as chimneys, venting heat and sucking in surrounding air to intensify fires, making their behavior more unpredictable and unstoppable.

Neil Lareau, a meteorologist at the University of Nevada at Reno, said he has never seen pyrocumulonimbus clouds on such a large scale.

A weather station in New South Wales recorded an air temperature of 158 degrees Fahrenheit as pyrocumulonimbus clouds advanced. That is roughly as hot as most saunas, though the number cannot be verified, because the instruments were not designed to work at such high temperatures.

In some spots, fires have restarted in areas that have already burned, said William Moomaw, a climate scientist at Tufts University in Massachusetts. “Basically, you’ve created a lot of charcoal” in burned forests, he said.

And they are nowhere close to dying out.

“This is a real wake-up call,” not just for Australia, but for the world, said Nerilie Abram, a climate scientist at Australia National University in Canberra. “We need to be looking at this and saying, ‘How much worse do we want to let this get?’ ”

The scale of this fire season is unprecedented, Australia’s Bureau of Meteorology said last week. Across the continent, 15 million acres of forest and farmland have been scorched. At least 25 people have been killed and a billion animals harmed. The fires in New South Wales are the largest in state history and have burned more area than has been ever been documented in eastern Australia.

The disaster is the result of climate change combined with an unlucky confluence of weather extremes. Australia has never been as hot and dry at the same time as it has been during the spring and summer of 2019 and 2020.

In December, Australia broke its high-temperature record twice in two days. A weather station in the Nullarbor, a desert region along the southeast coast, reported a high of 49.9 degrees Celsius, or 121.8 Fahrenheit, a national record for that month.

The country’s scale for measuring fire danger, known as the accumulated forest-fire danger index, was the highest on record in December. That means most of the country had turned into a tinderbox.

Without climate change, these scorching highs would not have been possible, according to Andrew King, a climate scientist at the University of Melbourne specializing in extreme events. Even with global warming, he was “astonished” to witness them.

“The temperatures we’re experiencing this summer I think many scientists didn’t expect to see for several decades yet,” he said.

By the end of December, the average temperature across the continent was 5.8 degrees Fahrenheit above the norm.

Australia’s record-setting heat and drought were caused by several factors.

From the west, a seesaw circulation pattern known as the Indian Ocean Dipole caused air to sink over Australia, heating and drying the continent.

Meanwhile, thousands of miles away and about 10 miles up, in the thin, frigid slice of the atmosphere on top of the South Pole, something shifted.

In an event that is unprecedented in 40 years of record-keeping, temperatures over Antarctica rose rapidly, causing the polar vortex over the Southern Hemisphere to break down and even reverse direction. This had cascading effects on weather patterns: The westerly winds that blow across the Southern Ocean shifted northward. Cold fronts moved across Australia, bringing intense wind but little rain.

These factors “all came together to create a really bad situation,” said Amy Butler, a researcher at the Cooperative Institute for Research in Environmental Sciences in Colorado.

Scientists say the dramatic events unfolding in Australia illustrate the kinds of disasters that will soon confront the rest of the world.

“Australia: you have just experienced the future,” tweeted Ed Hawkins, a climate scientist at the University of Reading in England.

The island continent is the hottest inhabited continent, and its unique geography means it is “highly exposed” to climate change’s influence, said Brendan Mackey, a climate scientist at Griffith University in Queensland. It will not take much warming to push life there from a comfortable existence to the edge of extinction, he said, making it something of a bellwether for the warming world.

Though the planet has experienced, on average, 1.8 degrees Fahrenheit of warming since preindustrial times, Australia in 2019 was 2.7 degrees warmer than average.

And those are just averages, Australia National University’s Abram pointed out.

“We tend to have this idea that our climate is gradually warming and these types of impacts will be gradual . . . but the Earth system doesn’t work like that,” Abram said. “There’s no reason to expect that a gradual increase in temperature will contribute to a gradual increase in the types of fires we’re having to fight.”

“It’s quite scary,” she added.

By turning forests that once absorbed carbon into flaming carbon sources, the wildfires are contributing to the very problem that makes them more likely. Satellite observations suggest that emissions from the fires may be on par with what Australia produces annually by burning fossil fuels.

The weeks of living under fire’s unrelenting threat have exhausted Young, the forest expert. Like her neighbors in her coastal village of South Durras in New South Wales, she keeps an emergency kit packed and has picked out a spot on the beach, tucked under a cliff, where she and her husband might hide if the inferno overtakes them.

In early January, after forecasters predicted particularly dangerous fire weather, the couple evacuated. The fires have been advancing so quickly — often as fast as 40 mph — that waiting to see flames was not an option.

When they returned two days later, “my house was still standing,” said Young, the head of the climate program at the Australian Rainforest Conservation Society. “The luck of three wind changes, quite literally.”

But better than most people, Young knows the danger is far from over. In the past, January and February have been the hottest months in southeast Australia. As climate change advances, the future will probably be even worse.

“We are heading off into completely unknown territory,” Young said. “Many more extreme or catastrophic days lie ahead.”