Wildfire smoke is warming the planet more than previously thought, scientists say

The wing of an airplane hangs over the right side of the image, a dimmed sun shines behind brown smoke above a dark, mountainous landscape.
Researchers collected smoke samples of three wildfires burning in Arizona, Idaho and Oregon in July and August of 2019. Results show a new type of particle, termed dark brown carbon, could be a significant contributor to global warming. (Image credit: NOAA/Steve Brown)

Among the complex mix of particles that make up wildfire smoke, an abundant but thus far unknown kind has been shown to trap a surprising amount of heat, according to new research. 

These results indicate that wildfires, which are expected to become harsher and more frequent in the coming years due to human-induced climate change, are heating Earth to a greater extent than previously thought.

Using NASA's Douglas DC-8 aircraft, which is a 54-year-old quadjet (a jet powered by four engines) that was turned into a flying science lab, scientists performed smoke analysis of three specific lightning-caused fires. All three had burnt large swaths of land in the western United States in 2019 — the Shady Creek in Idaho, Castle and Ikes in Arizona and the 204 Cow of Oregon. 

Their findings showed that a new kind of particle associated with these fires, dubbed organic "dark brown carbon," strongly absorbs heat — so much so that they account for more than half of the total heat absorbed by the collected wildfire smoke.

"It's likely that they form similarly to soot in the high-temperature flames along the leading edges of wildfires," Rohan Mishra, an associate professor of mechanical engineering and materials science at Washington University in St. Louis, Missouri and a co-author of the new study, said in a statement.

In July and August of 2019, scientists used instruments onboard NASA's flying science lab to collect smoke samples at about 6.2 miles (10 km) above ground. On ground, they used a mobile laboratory to collect samples of wildfire smoke about 1.8 miles (3 km) from selected fire management areas.

Related: Satellites watch as wildfires rage across Greece (photos)

Granite Gulch Fire, during August 2019. (Credit: NOAA OMAO)

The new particles are fewer in number when compared to another wildfire smoke particle known as black carbon or soot, which absorbs sunlight, then turns that sunlight into heat. Black carbon is the second largest contributor to global warming after carbon dioxide — however, these newly studied dark brown carbon particles appear to be four times more abundant in smoke than black carbon. That ultimately spikes the potential for wildfires to warm our planet far beyond what has been accounted for.

The results of this latest research, which was a collaboration between NASA and the National Oceanic and Atmospheric Administration (NOAA), add a strong urgency to better understand the warming effects of brown carbon. These particles are technically included in existing climate models, but their warming effects remain a huge uncertainty, and it's also worth noting that they're released into the atmosphere during the burning of fossil fuels as well. 

"Typically, climate models ignore or dismiss organic carbon as insignificant compared to black carbon when it comes to warming, but that is not what field observations reveal," Rajan Chakrabarty, an associate professor of energy, environment and chemical engineering at the Washington University in St. Louis and the new study's lead author, said in the statement.

The newly found particles seem to absorb light across the visible spectrum, from ultraviolet wavelengths to near-infrared. They are also capable of resisting light-induced bleaching, which is a naturally occurring process that's expected to strip brown carbon particles of their capacity to absorb heat, usually within a day after they're released into the atmosphere. 

However, lab experiments showed that the dark brown carbon particles indicated no change in heat absorption for at least three days.

Previous research has shown that such bleaching is "heavily dependent" on the height of the smoke and local atmospheric conditions. Closer to the ground, where there are higher chances of warm and humid climates, brown carbon loses its color or bleaches in as quickly as a day. 

The higher the wildfire smoke is from the ground, the cooler the air gets, so brown carbon in the smoke loses its water content, making chemical reactions that much harder. At high altitudes, it wafts in the atmosphere for as long as a year.

In the past, wildfire smoke has drifted to polar regions, and brown carbon was cited as the leading contributor to the accelerated melting of glaciers and sea ice in the Arctic, which is now warming faster than the rest of the planet.

The new paper was published on Monday (Aug. 07) in the journal Nature Geoscience.

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Sharmila Kuthunur
Space.com contributor

Sharmila Kuthunur is a Seattle-based science journalist covering astronomy, astrophysics and space exploration. Follow her on X @skuthunur.

  • alangloi
    DC-9 was a dual engine mounted to the rear of the aircraft. NASA has a DC-8 Airborne Science Laboratory which has four engines that are wing mounted.
  • Atlan0001
    Environmentalists need to stop piling up the underbrush to start fires then. Just as they need to stop piling up EVs to start fires that burn so fast people can't get out in time and firemen can't put out for hours or days. Then there is all that dead life and dying ecosystems around environmental projects like wide area land and sea wind farms and landed solar farms.

    Then there is the physic "time is money." As Napoleon said, "I'll give you anything but time!" So much wasted time. So much time lost. So much lost energy and economy, and infrastructure and cohesiveness of civilization being lost.

    And a great Frontier of breakout, Genesis (Creation) and Exodus, behind -- to the other side of -- a world class wall of Orwellian Iron Curtain . . . from the same all enclosing, closing, systemic dumbed down fanatical total authoritarian source as Environmentalism. The source, the same source, bent upon the total quality management and control of All Mankind. The problem for the totalitarian state will be Murphy's Law, the law of unintended consequences of power corrupting in One World-ism, in the "war of a thousand (a million, billion, trillion....) little cuts."
  • Classical Motion
    I wouldn't be looking for environmental situations/conditions or even mis-management. Although modern management has cause nothing but problems. The application and/or the research and conclusions......has been a very expensive failure. And they insist upon feeding it. This failure.

    If it's anything like here in the US, I would be looking for an arsonist. Several perhaps a group.

    But I'm paranoid. So, I could be wrong when I think our problems have been organized.
  • Atlan0001
    Classical Motion said:
    I wouldn't be looking for environmental situations/conditions or even mis-management. Although modern management has cause nothing but problems. The application and/or the research and conclusions......has been a very expensive failure. And they insist upon feeding it. This failure.

    If it's anything like here in the US, I would be looking for an arsonist. Several perhaps a group.

    But I'm paranoid. So, I could be wrong when I think our problems have been organized.
    ("Power tends to corrupt and absolute power corrupts absolutely" -- British Lord Acton)

    What life cannot divide outwardly; life will divide inwardly. In a closed system, division (null unity) will take its equal but opposite half-portion of the universe literally out of the guts of unity. And I don't mean unity doing subdivisions of a continuing unity which isn't equal. Even universe divides out into equalities (full individualistic equalities) of multiverse universes (an Infinite MULTIVERSE Universe of infinities of universes). Stephen Hawking, correct in the extreme, gave a Mankind without Space Frontier a very optimistic maximum of 1,000 years to mass extinction. -- Atlan0001.
  • poweber
    Thought provoking article, not-with-standing the 4-engine McDonnell Douglass DC-9, but I quote the author’s obvious bias with “wildfires, which are expected to become harsher and more frequent in the coming years due to human-induced climate change” followed by “smoke analysis of three specific lightning-caused fires” implying that humans caused the lightning. By what method did scientists, or criminals, create the lightning? Just askin’!
  • Ken Fabian
    How many people demonstrate no understanding of the difference between immediate cause (what lights a fire) and susceptibility to fire (what makes it hot and dry)?

    We had the "it's arsonists" line in Australia during and after the last very bad fire season but subsequent investigations found very little arson, with bad judgement, electrical faults and dry lightning the far more likely proximate (what lit them) causes. This affected area had experienced record breaking droughts (how dry) and extreme temperatures (how hot) before a fire was started by lightning. A nearby previous one was by misjudgement - someone foolishly lit a bin of rubbish during very hot and dry conditions. Anywhere people live there will be things that start fires.

    The "environmentalists prevent undergrowth removal or burning off" line was popular too with those seeking to reject connections with global warming - and false.

    Public safety concerns, public liability concerns, especially with more small holdings with inexperienced and poorly equipped landholders who - not surprising - are reluctant to light fires they are not resourced to control, especially of large areas, are much greater impediments than environmentalists - who largely support the use of fire to maintain native vegetation. Add in the limited resources for forest management - that do a lot of the largest areas of burning off -and it gets harder to keep up. Even without the warmer Winters shrinking safe opportunities. Regional fire authorities decide on large area fuel reduction fires and when they say no it is almost always about public safety not "green" regulation.

    Shorter periods of opportunity to conduct burning off safely due to warmer winters is a real thing, of serious significance around here - we used to reliably get cool overnight conditions that laid down natural fire retardant (dew), so fires lit in afternoons would be going out or easily controlled by morning. Those conditions are getting rarer - a single degree different can make a big difference in this.

    I've been conducting small burns around our home (and adding a fire sprinkler system) with no environmentalists trying to stop me and I'm seeing the opportunities to do so (right now) shrinking fast in the face of warm Winter weather; larger and much better equipped efforts are already getting out of control. After 3 la Nina years the post fire regrowth was exceptional and now it is drying out fast, with el Nino making the odds favour hot and dry. With some global warming extra
  • Atlan0001
    Ken Fabian, stop talking as if what you are going through there is "global!" I'm reading and hearing that constantly from those in power who would manage and control all Mankind and all its thinking and activities the world over. Where I live, we are going through a cooler and somewhat wetter than normal length of summer which may point, like it has before, to a longer, colder and more snowy winter than usual to come.

    You, and those others who want life and death power over us, want to blame the sun's blowing more heat toward Earth on Mankind. You want to blame a growing change in tectonic and sub-crust activity on Mankind. It is sheer tyranny you talk and that has bad consequences for elites as well as the masses of the lower classes they would rule (inevitably for the worse).

    I advise you to fight for, war (benignly) for, the occupation, colonizing, and opening of -- life's expansion to -- the frontier. And I don't mean colonization of the Moon or Mars or any other rock. I mean PCs: personal stations, colonies, and other man-made to order in-space facilitations! Going manmade smaller micro-world and micro-galactic, in order to go faster, sooner, and vastly larger in frontier. Either that or you and yours, and all the rest of Mankind, as a matter of enclosing closed systemic shrinking of minds and other dark age unintended consequences, will have a far worse, far more malignant war on your hands.

    Everything that is happening is pointing to the fact that we are nearing the end of a warming interlude, verging on a new long-term ice age . . . not a "little ice age," but the real thing, the norm of the Earth now. Even the sun in its excess of activity at this time is pointing that way to a long spell of hibernation from that excess of activity. The change in ocean current flows is particularly pointing to coming ice age as those who have studied and know its history of activity have already pointed out. If anything, we in our unborn energetic and polutionary (sic) incubation of growth in vast Space Age birthing energies, structures, infrastructure, complexities and reaches, temporarily obstructed the onslaught, but that is definitely coming to an end.