Australia has become an inferno. More than half of the country is choking on smoke, and the skies glow orange as bushfires continue to ravage the continent.

Since the start of the bushfire season in September, an estimated 25.5 million acres have burned in Australia, according to Reuters, and at least 25 people have died. More than 1 billion animals are feared dead, and an estimated 2,000 homes have been destroyed. Hundreds of thousands of people have been forced to evacuate.

The total damage and economic losses will exceed $100 billion, according to Accuweather.

Australia experiences fires every fall, but this year's crisis — which comes on the heels of a heat wave and prolonged drought — is unprecedented. By comparison, the fires that plagued the Brazilian Amazon last year burned 17.5 million acres of rainforest, which is 7 million fewer acres than the impacted area in Australia. (However, most of the Amazon fires were deliberately set by ranchers and loggers looking to clear land, whereas Australia's bushfires mostly started due to natural causes.)

A satellite photo of Bateman Bay on the southern coast of New South Wales, Australia, on December 31, 2019. Copernicus EMS

The fires could be part of an ominous feedback loop: The more land burns, the more carbon dioxide gets released into the atmosphere, and the more trees — which act as natural carbon sinks — disappear. Already, Australia's fires have released 350 million metric tons of CO2 into the atmosphere. That's roughly 1% of the total global carbon emissions from 2019.

The more CO2 gets released, the warmer our planet gets; that raises the risk of more big and deadly fires.

An area the size of South Korea is burning

It's hard to comprehend the size of the affected area in Australia. Added up, the burned land is the size of South Korea or the US state of Virginia.

Compared to the amount of land that burned during California's 2018 wildfire season — its most destructive ever — Australia's acreage total is more than 13 times bigger.

A smoke plume 1.3 billion acres in size

The area of the resulting smoke from the fires — 1.3 billion acres — is equal to the areas of Alaska, Texas, California, Montana, New Mexico, Arizona, Nevada, Colorado, Oregon, Wyoming, and Michigan combined.

The plume has reached South America and probably the Antarctic as well, according to the UN World Meteorological Organization.

Major Australian cities like Melbourne and Sydney have been engulfed in orange and yellow haze.

"I looked out into smoke-filled valleys, with only the faintest ghosts of distant ridges and peaks in the background," Michael Mann, a US climate scientist who is on sabbatical in Sydney, wrote in the Guardian on January 1.

A man looks at the smoky skyline on December 19, 2019 in Sydney, Australia. Jenny Evans/Getty Images

In December, a state official said New South Wales was experiencing the "longest" and "most widespread" period of poor air quality in the state's history.

A dangerous feedback loop

Dry conditions in Australia's bushland, wooded areas, and Blue Mountain National Park have made the land ripe for sparks. Australia experienced its driest spring ever in 2019. December 18 was the hottest day in the country's history, with average temperatures hitting 105.6 degrees Fahrenheit (40.9 degrees Celsius).

A firefighter battles flames outside Sydney, Australia, December 10, 2019. SAEED KHAN/AFP via Getty Images

In the last 15 years, Australia saw eight of its 10 warmest years on record. Winter rains, which can help reduce the intensity of summer fires, have declined significantly, The Sydney Morning Herald reported. This all meant that when the fire season started, it was savage and unstoppable.

"We used to see hundreds of thousands of hectares burned in bushfires, but now we are seeing millions on fire," Pep Canadell, executive director of the Global Carbon Project, told the Herald.

A firefighter sprays water after a fire impacted Clovemont Way in Melbourne, Australia on December 30, 2019. AAP Image/Julian Smith via REUTERS

The more forests burn, the more carbon dioxide enters the atmosphere, and the more heat it traps on the planet. To make matters worse, when natural carbon sinks like the Amazon rainforest and woodlands in Australia burn down, that reduces the natural avenues by which CO2 can get absorbed.

It's a vicious cycle.

In 2019, wildfires across the globe released approximately 6.38 billion tons of carbon dioxide into the atmosphere, according to the European Union's satellite observation program, Copernicus. That's about 17% of the global total for the year.

Until now, Australia's annual bushfires were pretty much net-zero in terms of greenhouse-gas emissions — the CO2 they emitted was balanced out by how much carbon-dioxide the country's forests sequestered. But in the last three months, Australia's fires have emitted roughly 350 million metric tons of CO2, according to the Herald. (By comparison, the Amazon fires produced less than half that: 140 million metric tons.)

Between 2013 and 2017, Australia's fires emitted 340 million metric tons of CO2 on average per year. This year's total has already blown past that, and Australia's dry season has another two months to go.

"Normally bushfires are thought of as 'carbon neutral,' but, in very simple terms, we're seeing climate extremes carry a double punch, with more frequent fire and drought," David Bowman, a fire-science expert at the University of Tasmania, told the Herald.

A firefighter hoses down trees and flying embers in an effort to secure nearby houses from bushfires near the town of Nowra in the Australian state of New South Wales, December 31, 2019. Saeed Khan/AFP/Getty

Canadell said he thinks the country's forests will need 100 years to return to the point where they can act as carbon sinks for fires of this size and scale.

Climate change is linked to more intense fires

Climate change increases the likelihood, size, and frequency of wildfires, since warmer air sucks away moisture from trees and soil, leading to dryer land. Rising temperatures also make heat waves and droughts more frequent and severe, which exacerbates wildfire risk, since hot, parched forests are prone to burning.

The sky is filled with smoke and ash on December 21, 2019 in Shoalhaven Heads, New South Wales, Australia. Cassie Spencer/Getty Images

"Climate change is exacerbating every risk factor for more frequent and intense bushfires," Dale Dominey-Howes, an expert on disaster risk at the University of Sydney, told Business Insider Australia. "Widespread drought conditions, higher-than-average temperatures — these are all made worse by climate change."

On average, Earth has warmed about 1 degree Celsius. July 2019 was the hottest month ever recorded, and 2019 will likely be the third-hottest year on record globally, according to Climate Central. Only 2016, 2015, and 2017 were hotter (in that order).

A helicopter drops water on a bushfire in scrub behind houses in Bundoora, Melbourne, Australia, December 30, 2019. AAP Image/Ellen Smith via REUTERS

"The brown skies I observed in the Blue Mountains this week are a product of human-caused climate change," Mann wrote in The Guardian.

He added: "Take record heat, combine it with unprecedented drought in already dry regions, and you get unprecedented bushfires like the ones engulfing the Blue Mountains and spreading across the continent. It's not complicated."