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Virginia Young knew the fires were coming. As an Australian forest expert, she had contributed to research predicting longer, 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, like wildfires, to mutate into more disastrous and deadly versions of themselves.

Temperatures are soaring to heights scientists didn’t 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, only to land in a flammable spot and start another fire.

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 — they’re sometimes called “devils” — and they can contribute to ember attacks, said Janice Coen, a project scientist at the National Center for Atmospheric Research.

The heat from Australia’s blazes has fueled fire-generated thunderstorms known as pyrocumulonimbus clouds. These mushroom-shaped clouds act like 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’s never seen pyrocumulonimbus clouds on such a large-scale.

A weather station in New South Wales recorded an air temperature of 158 F. as pyrocumulonimbus clouds advanced. That’s roughly as hot as most saunas, though the number can’t be verified since the instruments were not designed to work at such high temperatures.

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

Megafires, where two wildfires converge into one massive inferno, have also been reported. 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. “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 this week. Across the continent, 15 million acres of forest and farmland have been scorched. At least 25 people killed and a billion animals harmed. The current 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.

Without climate change, the scorching weather 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’s been “astonished” by them.