The worst of Australia’s wildfires have abated, but the brushfire season isn’t over with fires raging near capital city Canberra.
The devastating fires killed at least 30 people and an estimated 1 billion animals. Even as the fires subside, concerns over air quality are still pervasive and scientists are predicting long-term global impacts.
Intense wildfires aren’t new in Australia, but emissions from these fires rival the country’s total human-caused emissions, says atmospheric scientist Neil Lareau from the University of Nevada.
“It's really the scope, the size and extent of these fires, in addition to the severity that is quite remarkable,” he says.
The immediate impact comes from very small particulates within the smoke that can elude most humans’ natural filtration mechanisms, he says. The particulates can get deep into the lungs, diffuse into the bloodstream and cause cardiovascular impacts in addition to difficulty breathing.
Researchers are seeing effects like this on “vulnerable segments of the population” when large-scale events like wildfires hit highly populated areas, he says. Studies on fires in Southern California have shown negative health incomes such as decreased birth weights, he says.
On top of the health and psychological impacts on humans, these particulates can also worsen wildfires, he says.
“In addition to the particulates that you're breathing, these plumes are lofting burning particles of ash in what we call firebrands,” he says, “which can then land in advance to the fire front and rapidly spread the fire through the landscape.”
On scientists’ concerns regarding the atmosphere
“We have two parts of the atmosphere that we're concerned about. The troposphere, which is close to the surface. This is where all the weather is occurring. And then the overlying layer is called the stratosphere. And what we see with these intense fires is that they generate their own thunderstorms to effectively double the height to which the smoke will be injected into the atmosphere and can push it deep enough that it ascends all the way up into that stratospheric layer.
“And once it's there, it can stay there for a prolonged period of time, sometimes five, six, maybe even a year-long period … we can track these plumes of smoke, aerosol circling the globe. In fact, we know already that the smoke is fully encircled [in] the Southern Hemisphere going back to some of the events started in December and are continuing now. This is stuff that's going to stay there for a long time because there's no mechanism to remove it from the atmosphere once it gets that deep.”
On the problems caused by this smoke entering the stratosphere
“It may not be something that we're immediately breathing. What it is doing is interacting with sunlight coming into the Earth's climate system. And in this case, it's actually absorbing some of the sun's energy higher up in the atmosphere, in the stratosphere, and warming the stratosphere a little bit. It's also decreasing the amount of sunlight that's reaching Earth's surface. And so there's this is kind of complex interaction that could have kind of climate scale impacts and certainly regional impacts on the temperature of Earth, the temperature of the upper atmosphere. And some of these impacts are not fully understood at this point, especially since we don't have a lot of documentation for events of this magnitude. There's really just a few of these increasing understanding of the impact that they're having, but a whole lot of work still to be done.”
On whether the dangerous particles can travel elsewhere
“Probably not in any appreciable concentration that would be problematic from a kind of human health standpoint. Most of this stuff is traceable in the deep upper atmosphere for five to six months. And after that, it becomes so diffused that it would be difficult to really identify it beyond that point. But again, it's not fully understood at this point.”
“It's kind of a mix. And again, there are a number of potentially competing influences here. The carbon dioxide is a gas that's emitted into the atmosphere and can remain in the troposphere and can remain relatively well mixed and contributes, generally speaking, to the greenhouse effects — although it's quite complicated by how much of that is going to be reabsorbed by the growth of new vegetation following these fires. And that's kind of different than the particulate matter, these aerosol particles that are getting injected very deep into the atmosphere and can have these kind of radiative effects where it's intercepting sunlight. And some of those signals are actually kind of competing. In the one sense, carbon dioxide can be warming the lower part of the atmosphere. On the other hand, some of these smoke particles are intercepting sunlight and can either warm the upper atmosphere or potentially cool the lower atmosphere. So, again, there's a kind of complex chain of interactions that we're still working to tease out how all of that is going to balance out over time.”
On whether this makes flying in an aircraft dangerous
“Yes. So this is a great question. Flying through these clouds in these deep plumes as they're ascending on their way to the stratosphere could be potentially very hazardous for aircraft. We saw there was a Qantas Airlines flight that had encountered severe turbulence as it flew through one of these developing clouds and had to make an emergency landing. And we know from some of the research that we've done here in the United States, looking inside these clouds with radars, that they can have updrafts speeds upwards of 130 miles per hour, flanked by downdrafts as strong as 60 miles per hour. So you can imagine the kind of whiplash effect that would have on an aircraft flying through something like that. And it's really as strong as the updrafts in Earth's strongest thunderstorms and certainly not somewhere you'd want to be flying an aircraft.”
This segment aired on February 6, 2020.