Smoke from wildfires in Canada, Alaska, and the Pacific Northwest led to numerous air quality advisories across the region last month. As wildfires become more frequent and intense, such smoke events are expected to occur with greater regularity.
Dr. Derek Mallia, Professor at the University of Utah's Department of Atmospheric Sciences, studies wildfire behavior and smoke dispersion. He spoke with Rocky Mountain Community Radio's Maeve Conran about how the smoke can travel from so far away.
Dr. Derek Mallia: These wildfires are burning very large areas of biomass. It's burning a lot of forest, there's a lot of material being consumed by these sometimes very large wildfires that can be on the order of 100,000 acres, if not greater.
So if there are multiple of these fires ongoing at once, that's a lot of biomass you’re consuming, that's a lot of smoke being injected into the atmosphere. And so that increases the likelihood that smoke will be transported further downwind. And so that would be the first factor that's driving this.
Another thing is that wildfires act like chimneys where the smoke is emitted at the surface. Wildfires have what they refer to as the wildfire plume rise, which is a buoyant column of air that carries the smoke from the surface to very high levels into the atmosphere, in some cases, up to cruising altitude for let's say, an aircraft. And so this allows that smoke to be transported really far up into the atmosphere and it increases the likelihood that it can be transported into things like the jet stream and so on. And the jet stream, for example, can carry that smoke far downwind.
These smoke particles are also really small so if you loft them really far up into the atmosphere, it takes a lot of time for gravity to settle out these smoke particles. If these smoke particles are lofted further up into the atmosphere essentially they stay in the atmosphere longer and it increases the likelihood that they can be transported further downwind as well.
Maeve Conran: So how much more of these sorts of smoke events are we going to see where smoke is coming from, not just our region, but far away, or are we just looking at a very smoke-filled future?
Dr. Mallia: I think we are going to see more smoky days. I think it's, to some degree, a little bit difficult to pinpoint exactly how many more smoky days we will have per year and there's still a lot of ongoing work in that space.
But there are two compounding factors. There’s, of course, climate change, which is a really big driver of fire activity. Climate change results in warmer temperatures and therefore basically that increases the likelihood that these fire fuels will be drier, more stressed, and easier to burn essentially. And so that will allow the fires to consume more forest per unit area, but also grow larger in terms of its area. So that on its own will definitely result in more wildfires. It will also enhance the effect of that chimney effect that I described earlier, where if the fire burns hotter, it'll loft smoke further up into the atmosphere as well.
But then there's also the compounding factor. The fact that fire suppression has also resulted in the accumulation of dead biomass at the bottom of the forest, so whenever you have a fire that started, in addition to it burning more fuels and more vegetation and so on, because things are drier due to climate change, there's actually more stuff to burn because fire suppression has resulted in the accumulation of a lot of vegetation under the forest. As a result of that, there's more stuff to burn as well.
We're probably going to see more smoke going into the future due to both of those factors. As of right now, the climate change snowball is already rolling so therefore, even if we drastically start cutting carbon emissions now, we'll definitely see more wildfires and more smoke as a consequence of that given by what we're already seeing with the dryness of the Western U. S., for example.
Conran: Are there other climate change connections with smoke insofar as when wildfires occur, is carbon then being released up into the atmosphere? Is the smoke itself actually generating impacts that are exacerbating climate change? Are wildfires themselves actually contributing in other ways to climate change?
Dr. Mallia: So what you're getting at is a positive feedbacks connection—that's a terrific question. In regards to fires creating their own weather that's very much that chimney effect. Those fires, those plume rises that I was talking about before, can sometimes be so large that they can generate their own thunderstorms. So we call those fire-initiated thunderstorms or pyrocumulonimbus clouds which are basically fire-initiated thunderstorms.
Linking this back to the broader climate question, which is we're emitting a lot of smoke particles into the atmosphere, you can imagine how that will maybe impact Earth's radiation budget. And so when I say radiation budget, I mean, basically, we get energy from the sun. But there are a lot of things in the atmosphere that can alter that kind of energy budget so that could be greenhouse gasses, for example, smoke particles, or just particles in the atmosphere, in general, that can also impact this kind of energy budget.
Wildfire smoke has a lot of what they refer to as black carbon in it, and that black carbon is really efficient at absorbing energy coming from the sun. So, it is possible that wildfires could actually result in an additional kind of warming effect due to the presence of black carbon in the atmosphere.
I think there have been some preliminary studies that have started to look at that. In the grand scheme of things, it's probably a pretty small percentage, but something that needs to be looked at more and investigated more thoroughly.
But there could be some additional warming just due to the presence of more wildfire smoke in the future, granted, that signal is going to probably be pretty small relative to the signal, just having more greenhouse gasses from human emissions, but it is probably something that you don't want to neglect. I would call it a more second-order effect relative to the other kinds of things that are driving climate change.
Conran: A lot of times when we talk about tackling the climate crisis, reducing emissions, reducing carbon consumption, all of that, I think a lot of people think, ‘well, that's quite long-range, but right now we're living through smoke and we need something more immediate.’ Is there research being done into what can be done for air quality in a more immediate sense? If we are, hopefully, long-range trying to reduce emissions in the long run, is there anything that can be done in a more immediate sense?
Dr. Mallia: The fire suppression issue is something that could be a little bit more manageable and something we could tackle. One way that we can try to reduce smoke emissions from fires is by reducing the intensity. One effective way of doing that would be to have more prescribed burns during the off-season where these fires burn at much lower intensity. What we can do is thin out the underbrush in a forest so that when a wildfire does occur during the hot summer, it's going to burn less intensely. It'll be much easier to manage if needed and so on.
So that is still something that would take time, but that might be on the order of a decade versus climate change where we're talking about 50 to 100 years before we can wrangle that in and maybe get carbon emissions to that pre-industrial era. Along those lines, I would just say that prescribed burns and trying to thin out these forests, to do a better job managing our forests, would probably be a reasonable first step. But even that is going to be difficult as well.
Unfortunately, I don't think there is an easy solution for tackling this kind of smoke issue. One of the things that we can do is take smoke and air quality more seriously. For example, people take hurricanes, tornadoes, and thunderstorms relatively seriously but I think smoke should also be thought of as severe weather in that it has negative health consequences for those exposed to it outdoors. On a smoky day, you would treat it like a rainy day where you probably want to be indoors as well and at least have access to clean indoor air quality. HVAC systems can help with that, but not everyone has access to central air and so on.
So that's another way to think about it. And of course, if we're going to be telling people that, we have a couple of smoky days coming up in the next 3 to 5 days, we can't just let look at a map right now and be like, “Oh, that's what the air quality will definitely be for this region” so, we need to develop forecast models that can better forecast smoke like we do for rain events. The way I think about it is, smoke is weather. It's just different and I think in the past we haven't given it as much thought. It was almost, and even in the meteorological community, I think they're almost thought of as two different topics. And it's in the atmosphere, it's something that we care about and it’s something that impacts our health. Therefore it should be treated just like any other kind of weather phenomenon.
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