More Wildfires = More Warming = More Wildfires

July 29, 2013


Chris Mooney in Mother Jones:

Scientists have known for some time about the risk of large-scale carbon emissions from thawing permafrost. But in recent years, they’ve become increasingly attuned to an additional—and very worrisome—aspect of this threat. As climate change proceeds, larger and more intense wildfires are increasingly scorching and charring the forests of the north. While these fires have always been a natural and recurring aspect of forest ecosystems, they now appear to be undergoing a major amplification. And that, in turn, may further increase the threat of permafrost thawing and carbon releases—releases that would, in turn, greatly amplify global warming itself (and potentially spur still more fire activity).

“You have this climate and fire interaction, and all of a sudden permafrost can thaw really rapidly,” explains Jon O’Donnell, an ecologist with the National Parks Service’s Arctic Network. Scientists call it a “positive feedback,” and it’s one of the scariest aspects of global warming because, in essence, it means a bad situation is making itself worse.

When it comes to understanding the wildfire-permafrost feedback and just how bad it could be, one factor is clear: Wildfires are definitely getting worse. “The area burned by wildfires has been increased quite a bit over the last couple of decades,” says Terry Chapin, a biologist at the University of Alaska-Fairbanks. Indeed, a new study just out in theProceedings of the National Academy of Sciences suggests that recent fire activity in these “boreal” regions of the globe is higher than anything seen in the last 10,000 years.

Fires are also becoming more severe, says O’Donnell. Finally, the seasonality of fires appears to be changing, with burns extending later into the summer, when permafrost has thawed more completely—once again, amplifying the overall impact of burning on frozen soils and the carbon they contain.

And here’s where the feedback kicks in: Large northern fires don’t just burn huge swaths of forest. They can also burn off the upper layer of lichen and mosses on the forest floor. When intact, this forest surface layer insulates the underlying permafrost and protects it from thawing—but getting rid of it takes away that protection, even as it also exposes the area to the heating of direct sunlight.

Plus, there’s an added effect: After a fire burns through a region, O’Donnell notes, it leaves behind an area of the earth’s surface that is blackened in color. And these dark areas absorb more heat from the sun, thus further upping temperatures and thawing permafrost. As the soil thaws, meanwhile, microbes have a much easier time decomposing its organic matter. “The microbes can start to crank on that carbon,” says O’Donnell, adding that the process results in the release of carbon dioxide to the atmosphere.



6 Responses to “More Wildfires = More Warming = More Wildfires”

  1. Sir Charles Says:

    More positive feedbacks. Wait till the Tundra and deep oceans are releasing more methane…

    There’s a lot to come still in the pipeline.

  2. xraymike79 Says:

    Reblogged this on Collapse of Industrial Civilization and commented:
    While we’re on the subject of methane and feedback loops, the fires are growing more destructive in the boreal regions of the North, in fact worse than at any time in the last 10,000 years. These fires decrease the region’s albedo effect by blackening the Earth’s surface and peeling away the insulating layer of lichen and moss on the forest floor, exposing the underlying permafrost to accelerated thawing and microbial decomposition of the soils. These infernos result in an immediate release of methane and CO2 from the fires themselves and later from the freshly exposed permafrost below.

  3. ahaveland Says:

    Suggested title for new book: “Unterraforming for dummies”

    We could nuke the ice sheets too just to help things along…

  4. According to an email I received last year from John Mitchell of the UK Hadley Centre, feedbacks from increased forest fires are not in the climate models. (I think that will also apply to the fires described above and would include the CMIP5 models used for the coming AR5 report from the IPCC.) JM said

    5. more forest fires
    5 we don’t do yet, but could be important for changing ecosystems response to climate.

    6. melting permafrost
    6a/b [GB – a:CO2, b:CH4] we don’t have in the GCM, but have some simple modelling of. Too early to show any results yet, but we plan to publish later this year. Bottom line is that both CH4 and CO2 will be released as permafrost thaws. The magnitude is uncertain, but likely to be significant.

    7. increased decomposition of wetlands
    7, we have in HadGEM2 but didn’t enable as a fully coupled feedback, but we can diagnose changes in wetland extent and CH4 emissions

    I would add that although these things may be important, they are not always easy to quantify, model, initialize and validate, especially 5-7. That is why is taking time ot implement them.


  5. = more smoke = more particulates = more cooling?

    • Yes, no, yes, no and no.
      It depend on a number of factors.

      The direct effect on radiative forcing blocking light-Cooling
      During the Yellowstone National Park fires in northwestern Wyoming in 1988 (determined from satellite imagery). As these smoke clouds passed over the midwestern United States for the Canadian and Yellow-stone fires and over Alaska for the Chinese/Siberian fires, surface air temperature effects were determined by comparing actual surface air temperatures with those forecast by model output statistics (MOS) of the United States National Weather Service. MOS error fields corresponding to the smoke cloud locations showed day-time cooling of 1.5° to 7°C under the smoke but no nighttime effects.

      (Day cooling but not at night.)

      Also on the size of the partials. The indirect cooling effect (making clouds more reflective) is the way in which the tiny particles directly scatter and reflect incoming sunlight back to space. Called the “direct effect,” but smoke from WF are larger so less direct effect cooling.

      (Less direct cooling because of large size.)

      “Semi-direct aerosol effect on clouds”—the process by which dark-colored aerosol particles (i.e., the soot in smoke) absorb incoming sunlight and warm the atmosphere relative to the temperature of the surface. Reduces the upward movement of moisture and, in turn, reduce cloud cover. It is also called the “cloud-burning effect of soot.” a semi-direct affect on cumulus clouds over the ocean. Fewer clouds means more solar energy enters the Earth system, which amplifies the warming effect caused by suppressing the formation of low-level cumulus clouds.
      It does this by accelerating the process of evaporation of existing clouds, and by suppressing the upward flow of moisture from the surface needed to form new clouds.

      Also you have a direct warming of soot on snow or lighter surfaces.

      Volcanoes Pinatubo’s aerosol output completely canceled out greenhouse gas warming for almost two years. It hurled a huge amount of sulfur dioxide 10 to 50 kilometers up into the atmosphere. (It did not have the other factor becasue it was in the Stratosphere).

      If you look at the effects of forcing in the IPCC you will notice that aerosols and clouds have some of the largest error bars. No one simple answer.

      The effect are:
      1) blocking light-Cooling
      2) cloud-burning effect of soot – warming
      3) direct warming of soot snow, ice, etc.

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: