Wild Fire Fact Check

August 21, 2018


Misinformation from deniers spreads, well, worse than wildfire.

Carbon Brief has a much needed corrective, from the always on-point Zeke Hausfather,  to some nonsense denial memes that have been making the rounds, in this season of off the hook wildfires.

Carbon Brief:

Recently, some commentators have tried to dismiss recent increases in the areas burnt by fires in the US, claiming that fires were much worse in the early part of the century. To do this, they are ignoring clear guidance by scientists that the data should not be used to make comparisons with earlier periods.

The US National Interagency Fire Center (NIFC), which maintains the database in question, tells Carbon Brief that people should not “put any stock” in numbers prior to 1960 and that comparing the modern fire area to earlier estimates is “not accurate or appropriate”.

Here, Carbon Brief takes a look at the links between climate change and wildfires, both in the US and across the globe. As with any environmental issue, there are many different contributing factors, but it is clear that in the western US climate change has made – and will continue to make – fires larger and more destructive.

As one scientist tells Carbon Brief: “There is no question whatsoever that climate plays a role in the increase in fires.”

According to data from the NIFC, there has been a clear trend in increased area burned by wildfires in the US since the 1980s, when reliable US-wide estimates based on fire situation reports from federal and state agencies became available.

Today, wildfires are burning more than twice the area than in the 1980s and 1990s. These figures include all wildland fires in both forested and non-forested areas. Most of the area burned today is in the western US, where dryer conditions tend to allow for large, quickly-spreading wildfires.

The black bars in the top panel of the figure below show the annual area burned (in acres) by wildfires since 1983 when reliable data became available. The blue line shows the linear trend in fires over the same period. The bottom panel shows all of the data in their database, including pre-1983 values where the data is of poorer quality.

The NIFC explicitly warns users on its website: “Prior to 1983, sources of these figures are not known, or cannot be confirmed, and were not derived from the current situation reporting process. As a result, the figures prior to 1983 should not be compared to later data.”


Annual wildland acres burned since reliable data was available in 1983 (top panel) and area burned since 1923 (bottom panel) showing periods when quality of data was poor and incomparable. Blue line in top panel shows linear trend. Data from the US National Interagency Fire Center; Chart by Carbon Brief using Highcharts.

Those sceptical about the role of climate change in the recent increase in fires have pointed to the full dataset, trying to argue that the fire area has decreased by around 80% over the past century.

This is not an accurate comparison, according to Randy Eardley, a spokesman at the NIFC. As he tells Carbon Brief:

I wouldn’t put any stock in those numbers. To try and compare any of the more modern data to that earlier data is not accurate or appropriate, because we didn’t have a good way to measure [earlier data]. Back then we didn’t have a reliable reporting system; for all I know those came from a variety of different sources that often double-counted figures. When you look at some of those years that add up to 60 or 70 million acres burned a lot of those acres have to be double counted two or three times. We didn’t have a system to estimate area burned until 1960, but it was really refined in 1983.

If 50m acres had actually burned in the early 20th century, it would amount to an area of land equal to the entire state of Nebraska going up in flames every year.

Eardley suggests that earlier records were inflated by including areas where fires were purposefully set to clear forests for agriculture, or where rangelands were torched to get rid of sagebrush to improve grazing conditions. Other federal reports suggest that most of the area burned between 1930 and 1950 was in southeastern US and were primarily intentionally set fires for clearing land.

While the early 20th century data is not reliable and likely double or even triple-counted actual fires, Eardley says that it is possible that fire extents were higher back then for a simple reason: there was no large-scale firefighting organisation in the first half of the 20th century. Therefore, fires would burn through larger areas before being extinguished or burning themselves out, particularly when they were not close to towns or settlements.

Today, the US has larger and more organised firefighting operations in place. Therefore, recent increases are not due to any change in firefighting approach. If anything, many more resources have been devoted to fighting fires in the past few decades than in any prior period.

US wildfires and climate change

The recent period of large wildfires in forested areas of the western US has coincided with near-record warm temperatures. The figure below shows spring and summer temperatures (May through to August) – the period that overlaps with fire season – for the western half of the US. Annual values are shown by black dots, while a smoothed average of temperature over time is shown in red.


While the dust-bowl era year of 1934 still holds the record for the warmest spring/summer in the western US, it was something of an anomaly compared to other years at the time. In contrast, modern temperatures are considerably higher than temperatures typical of the 1930s, as shown by the red smoothed average line.

Temperatures in the western US between March and July in 2018 have been at near-record levels, similar to the spring/summer temperatures for the past three years.

There are many different factors that contribute to forest fires in a given year, including how many fires are ignited (arson, lightning strikes, downed power lines, malfunctioning equipment, etc), where they occur, how high temperatures are, how low precipitation has been and wind conditions where fires occur. For any given fire, local factors will play a large role, but when aggregated across the whole western US the role of climate conditions stands out sharply.

In a 2006 paper published in Science, Prof Anthony Westerling at the University of California, Merced and colleagues examined the relationship between climate conditions and large forest fire frequency. They found that, while land-use history and “fuel-loading” – the amount of accumulated burnable vegetation – were important factors for specific forest areas, “the broad-scale increase in wildfire frequency across the western US has been driven primarily by sensitivity of fire regimes to recent changes in climate over a relatively large area”.

Westerling identified a clear link between changes in temperature, length of fire season and areas burned over time.


16 Responses to “Wild Fire Fact Check”

  1. Sir Charles Says:

    This certainly didn’t happen before 1960: A number of Swedish reactors had to shut down or reduce output as the summer heatwave sent temperatures to record highs in July, with the sea water that is used to cool them becoming much warmer than normal, exceeding safety levels. Sweden’s nuclear energy regulator has asked plant operators to produce plans in the coming months to shield their reactors from harmful hot weather.

    => Sweden calls for nuclear reactors to be shielded from hot weather

    I can tell you right now, Sweden isn’t close to the equator.

    • rhymeswithgoalie Says:

      “I can tell you right now, Sweden isn’t close to the equator.”

      Hm. Let me take note of that….

      • dumboldguy Says:

        Yes, DO take note—-I myself carry a card in my wallet titled “Important facts i wouldn’t have known if Sir Chucky hadn’t posted them”.

  2. indy222 Says:

    The wildfires in California have, witnessed by this Californian, been hellish. Smoke is now so widespread that even here in Santa Cruz, almost a hundred miles from any of the big fires, it is a smokey pall most days. Driving back from the Owens Valley over Tioga Pass west through Yosemite, it was as eery and post-apocalyptic as I’ve ever seen this once beautiful drive. Choking smoke, very few people, at the height of the usual tourist season, miles and miles of fireman-cut and burned logs along Hwy 120, still smoldering. The scars of past fires still obvious… there’s hardly any unburned landscape now from Crane Flat all the way down the Merced River and down Hwy 120 past the entrance to the Park.

    • dumboldguy Says:

      A real shame. Have visited Yosemite only once (1966) and entered from the east via Tioga Pass as you did. It was a beautiful clear sky drive in a trip that took us to many parks throughout the west. I wonder if we’ll ever see it that way again.

      Yosemite is not alone—check out the photos from NASA here. I was pleased (NOT) to hear that the smoke went high out west but will drop back to ground level by the time it reaches the east coast. Just what we need to go along with our increasingly common 6-inches-in-one-day rainfalls.


      • Sir Charles Says:

        Sign the petition: Denounce Trump’s dangerous rollback of Obama’s Clean Power Plan

        In the Trump administration’s latest egregious blow to the environment, Trump is unveiling a plan to “empower states to establish emission standards for coal-fired power plants”—which would result in releasing hundreds of millions of tons of CO2 (carbon dioxide) into the atmosphere.

        This power plant plan is in direct opposition to the Obama-era Clean Power Plan, a policy intended to combat climate change that Trump and former EPA administrator Scott Pruitt proposed to withdraw.

        Trump’s new plan would release at least twelve times the amount of CO2 over the next decade compared to the Clean Power Plan. It would only make small cuts to pollutant emissions—by 2030, Trump’s proposal would cut CO2 levels by 0.7 – 1.5%, compared to the 19% Obama’s plan would have reduced.

        This is no minor policy adjustment: Trump’s plan could affect more than three hundred power plants across the United States.

        To top it all off, Trump’s plan isn’t just outrageous—it’s dangerous. Scientists have warned of “increasingly dire climate effects” If we don’t take active steps to majorly cut carbon emissions.

        Rather than sticking with an environmentally-conscious plan, Trump has yet again chosen to destroy an Obama-era policy and harm the rest of the world while he’s at it.

        Sign now to denounce Trump’s rollback of the Clean Power Plan.

  3. Keith McClary Says:

    There is some opinion that increased wildfires may be due to decades of fire suppression, resulting in more fuel in the forests.

    • dumboldguy Says:

      There is some truth to that “opinion”. We are having a tough time getting anything right.

    • redskylite Says:

      Unfortunately Watts Up With That have been blaming decades of fire suppression for a few years now, and of course there are devilish people who seem to pursue deliberate arson Nether the less Climate change is certainly playing it’s part and WUWT steadfastly fails to mention the increase in temperature over the last few decades with increasing extremes of drought and floods. Blinkered minds or fossil fuel diehards as usual.

    • rhymeswithgoalie Says:

      Ignore the fact that the dry undergrowth is fueling the speed of these fires, and claim that commercial cutting of more trees is what’s needed.

  4. Brent Jensen-Schmidt Says:

    Bush fires in Australia at the height of winter! A helicopter pilot has died fighting them.

  5. Sir Charles Says:

    The extreme wildfires sweeping across parts of North America, Europe and Siberia this year are not only wreaking local damage and sending choking smoke downwind. They are also affecting the climate itself in important ways that will long outlast their flames.

    => How Wildfires Can Affect Climate Change (and Vice Versa)

  6. J4Zonian Says:

    ’Misinformation from deniers spreads, well, worse than wildfire.’
    It’s deliberate. I’d call it disinformation.

    ”Those sceptical about the role of climate change ”
    NOT skeptical but denying delayalist or denialist.

    Much fuel loading happening now in some areas is dead trees from pine beetles, spread by warming winter temperature caused by global warming.

  7. Denis Rancourt Says:

    This is my 2016 critical review of the science literature about the false fire-CO2-warming connection:


    “Anatomy of the false link between forest fires and anthropogenic CO2

    In this critical review of the scientific literature about fire, I describe how the false notion of a link between forest fires and anthropogenic CO2 was ignited in 2006 by a fatally flawed article promoted in the science-trend-setting magazine Science, and spread like wildfire through the scientific literature and beyond, driven in part by high winds of climate modelling extravagance, while fortunately leaving large unburnt patches. There is no evidentiary basis for such a link. On the contrary, established knowledge about forest fires leads to the conclusion that dedication to teasing out such a link is preposterous: In the present circumstances starting in approximately 1900, the dominant effect is direct human impacts on land use, which causes global fire occurrences to be dramatically less than from the known long-term natural cycles (modern fire deficit). No special circumstances or regions have been correctly identified where forest fire behaviour can be attributed to CO2. Canada’s recent Fort McMurray fire is no exception. The claimed 7 g mean birth weight loss arising from mothers’ general exposure to CO2-driven southern California wildfires, like all such claims, is a product of statistical and conceptual overenthusiasm. I use concepts from the animal-behaviour scientific literature to explain how some scientists and their followers can get so carried away. “

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