Superflares of fiery thunderstorms could change the Earth's climate, experts in Australia and the United States warn

Superflares of fiery thunderstorms could change the Earth's climate, experts in Australia and the United States warn
Superflares of fiery thunderstorms could change the Earth's climate, experts in Australia and the United States warn

Fire thunderstorms - which occur in pyrocumulonimbus (fire-breathing) clouds - not only create their own weather system, but can be powerful enough to actually change the climate, according to scientists from Australia and the United States. Phenomena arising in the atmosphere as a result of wildfires can lead to "nuclear winter".

The "superflash" of firestorms - also known as pyrocumulative events - released about 2,000 nuclear charges the size of Hiroshima in Australia's 2019-20 black summer fires, according to a study recently published in the journal Nature Climate and Atmospheric Science.

"The energy release was enormous," said Rick McRae of the University of New South Wales, co-author of the work.

"It doesn't matter what units you use, these are large numbers, much larger than we used to think."

In the case of a pyrocumulative fire (pyroCb), a bush fire becomes so intense that it alters the dynamics of vast areas of the surrounding atmosphere, creating a characteristic anvil-shaped cumulonimbus cloud high above the fire, emitting smoke and ash all the way to the stratosphere.

McRae and a team of researchers, including scientists at the US Naval Research Laboratory in Washington, estimated the magnitude of the Black Summer superflare and concluded that the fires emitted as much smoke into the stratosphere as a moderate-sized volcanic eruption. This smoke remained in the stratosphere for over a year.

"It really puts [Black Summer Superflash] in a very special niche in the range of extreme weather and terrestrial events," said Dr. Mike Fromm, an atmospheric scientist at the Naval Research Laboratory.

Volcanic winter

According to scientists, smoke and ash from large volcanic eruptions in the past have caused disturbances in the global climate.

When the Tambora volcano in Indonesia erupted in 1815, the cooling effects of smoke and ash caused what is called a "volcanic winter", resulting in crop failure and food shortages around the world.

Dr. Fromm said the cooling effects of smoke and ash in the upper atmosphere also underpin the "nuclear winter" theory.

"Nuclear winter" was the hypothesis that if enough city fires occur as a result of an atomic explosion, a plume [of smoke and ash] would form that would be dark and massive enough to linger in the stratosphere and cool the climate, "he explained.

"It was theory, and only theory, until we spotted the PyroCb phenomenon and [recorded smoke from the fires in the bush] in the stratosphere."

Fromm said PyroCb phenomena such as the Black Summer superflare are now being used to validate the "nuclear winter" theory.

In doing so, the study raised an unusual new question about the potential impacts of climate change.

"Could a series of large PyroCb outbreaks compete with the potential climate impact expected after a nuclear war?" the team asks in their magazine article.

“Of course, we don't have anything on the scale of an atomic explosion when it comes to these wildfires,” said Dr. Fromm.

“But in the case of these events [such as the Black Summer superflare], you have a scalable phenomenon.

"So if you zoom in 10x, 50x, or 100x, you can see if you get a plume the size of a nuclear winter and the [subsequent] effects."

Are wildfires causing global climate change?

Fire thunderstorm superflares are now becoming a potential feedback loop in the climate system, Mr McRae said.

He said climate change could lead to an increase in the frequency and intensity of extreme fires, which in turn could change the climate.

“With so much aerosol flying higher into the atmosphere, climate change models need to start taking this into account,” said Mr. McRae.

“If you’re modeling climate change, you’ll answer,“How many such events will happen in the fourth decade of the century?”To which you’ll answer,“It all depends on the feedback loop that your model gives.”So you are in a loop.

"People will have to start looking for ways to extrapolate … what we have learned from the Black Summer [wildfires] and North America now in order to get a realistic interpretation of what will happen in 2040 or 2060."

Fire thunderstorms in record numbers

Even more than Australia's Black Summer, 2021 marks a new record year for fire thunderstorms.

“This year, here in North America, we see firestorms almost every day,” says Canadian fire expert Mike Flannigan of the University of Alberta.

"Now they have become commonplace. They used to say about them:" Oh, this is really an extreme event."

At the moment this year, 46 confirmed - and one probable - pyro event have been registered in Canada, 11 in Russia, including three this week, in the USA - 15, in Australia - one, only 74 pyro events in 2021

Dr. Flannigan said PyroCb outbreaks this year have behaved in ways he hasn't seen in over 40 years of work in fire science.

"The PyroCb at Lake Sparks, British Columbia [early July] had thousands of lightning strikes, and this is the first time I've seen this many lightning strikes from a PyroCb," he said.

"And that has led to dozens of fires up to 50 kilometers downwind. This is the first time I've seen dozens of fires caused by pyroCb. So this is a whole new level of self-replicating fires," he added.

Dr. Fromm said he also suspects that the world might be witnessing something new.

“I really think 2021 set a new high for the number of pirocobs we recorded,” he said.

"For example, we saw an outbreak of 11 pyroCbs in Saskatchewan and Manitoba last week."

"So that monstrous outburst at Lake Sparks and then an event two weeks later in Saskatchewan might give us the idea that we are fixing something different in 2021."

Mr. McRae also wondered if scientists are seeing so many new and worrying fire behaviors just because fire observation technology has improved.

But in the end, he said the evidence was overwhelming.

“You reach a point where you cannot remain skeptical because there is so much evidence that things are changing. You have to try to stay ahead of the action, not just stick to what you’re used to,” said Mr. McRae

Black summer in North America

In Tasmania, fire scientist Professor David Bowman of the University of Tasmania is watching the fire season in North America increasingly resemble Australia's Black Summer.

"Once in a lifetime fires are becoming the norm" - he said.

According to Professor Bowman, asking if any one event is caused by climate change is asking the wrong question

“Looking at one phenomenon is a very convenient way to make a deadly problem seem less important,” he said

“The global picture of extreme fire activity needs to be considered. This is a major warning sign that the Earth's climate system is changing,” he said

Like Mr. McRae, Professor Bowman believes climate scientists need to better understand how fires can trigger climate feedback.

“Because our forests burn very often and very intensely, we are releasing the carbon stored in plants, wood and soil into the atmosphere. And we are accelerating climate change,” he said

Ensuring the safety of the population and firefighters

Mr. McRae fought fires in Canberra in 2003, a landmark event in the understanding of fire thunderstorms. He also witnessed the devastation left behind.

He said new knowledge about extreme fire behavior needs to be put into practice to ensure the safety of the public and firefighters.

"It's one thing to do scientific research. Now the real challenge is to disseminate this knowledge to people who can actually use it to mitigate the effects of climate change."

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