Climate Science Voyage of Discovery: Climate Attribution For Wildfires and the Science-Journalism Translation

We’ve heard wildfires are “caused by” “exacerbated by” “primarily” “significantly” by climate change in various stories and op-eds. So let’s trace these back to the studies.

The Society of Environmental Journalism sent me a link to these Science Facts put out by our friends at AAAS. Scientists reading this.. please register with Sciline here.

Top Line
Human-caused climate change is a significant contributor to the increasing size and intensity of, and damage from, western U.S. wildfires.

The Essentials
In the western United States human-caused climate change caused more than half the increase in forest fuel aridity (how dry and flammable vegetation is) since the 1970s and has approximately doubled the cumulative area burned in forest fires since 1984.

Now many of us might ask, how could you know that “across the western US?” Could there have been more vegetation due to lack of fire suppression, that led to less water for each plant and hence dryness of vegetation? Haven’t suppression tactics changed over that period? If logging is bad for fires, as some claim, then there’s been much logging since 1984, how does that factor in? How could these estimates possibly be considered “facts?”

But first let’s take an aside to point out two concepts that may get lost in stories.

1. Not everything about climate is AGW or anthropogenic climate change. As we’ve seen via Matthew’s graphs of PDO, there is much climate variability that occurs naturally. E.g., in my own part of the country about 100 years ago there was a serious drought that led to the Dust Bowl. So just because I’m experiencing heat, it’s not necessarily AGW.

2. And not all climate change is about carbon, nor even all greenhouse gases (GHGs). Land use changes such as albedo, irrigation, urban heat islands and so on can also affect climate, in complex and interactive ways we don’t yet understand. So we can’t go directly to “reducing carbon (alone) will solve the problem.”

To find the contribution of AGW, we have to look at attribution studies. These studies run climate models and try to find the fingerprint of AGW by what sounds like comparing the model results to real world observations of some kind. I recommend taking the time to read this one. Sure I don’t get all the details of CMIPs and so on, but we can all understand what data goes in, what comes out, and we can read the caveats, and the conclusions. We can also examine the almost magical transitions between the paper (careful), the interviews (not quite as careful) and the headlines e.g. “caused by.”

Here’s a typical exchange of scientists:

Swain with UCLA and other scientists earlier this year published a study that said climate change has doubled the number of extreme-risk days for California wildfires.

It said temperatures statewide rose 1.8 degrees Fahrenheit since 1980, while precipitation dropped 30%. That doubled the number of autumn days that offer extreme conditions for the ignition of wildfires (Climatewire, April 3).

The heat is expected to get worse with time. Climate models estimate that average state temperatures will climb 3 degrees Fahrenheit by 2050 unless the world makes sharp cuts in greenhouse gas emissions, said Michael Wehner, a senior scientist at Lawrence Berkeley National Laboratory.

Even with emissions cuts, average temperatures would rise 2 degrees by midcentury, he said.

Jon Keeley, a senior scientist at the U.S. Geological Survey Western Ecological Research Center, argued that the study from Swain and others failed to show that hotter temperatures are driving wildfires.

“Show us data that shows that level of temperature increase is actually associated with increased fire activity,” Keeley said. “They don’t show that.”

Keeley added, “We ought to be much more concerned with ignition sources than a 1- to 2-degree change in temperature.”

A big contributor to large California fires is that the state has focused on extinguishing blazes for about a century rather than allowing for controlled burns, he said. That has caused dead vegetation to accumulate.

Trump has accused California of failing to “sweep” its forests, which he has linked to fires in the state.

Keeley said that “we don’t sweep forests here in the U.S., but what we do is prescription burning. … It’s potentially the same thing. It’s modifying the fuels prior to a fire.”

Swain, the UCLA climate scientist, said global warming is affecting how big fires get and how fast they move.

“What happens when they start burning, what is the character of those fires, and is it changing?” Swain asked. “The answer is yes.”

If we look at the statements in the study, though..we get a “fingerprint for meteorological preconditions.” Not exactly “fires caused by climate change.”

Collectively, this analysis offers strong evidence for a human fingerprint on the observed increase in meteorological preconditions necessary for extreme wildfires in California.

In the present study, we do not quantify the relative role of increased urban and suburban incursion into the high-risk wildland-urban interface, nor the contribution of historical land/vegetation management practices to increasing wildfire risk or possible future climate-fire feedbacks

And sounding rather like Keeley..or any of the rest of us..

In the long-term, reduction of global greenhouse gas emissions is the most direct path to reducing this risk, though the near-term impacts of these reductions may be limited given the many sources of inertia in the climate system [78]. Fortunately, a broad portfolio of options already exists, including the use of prescribed burning to reduce fuel loads and improve ecosystem health [79], upgrades to emergency communications and response systems, community-level development of protective fire breaks and defensible space, and the adoption of new zoning rules and building codes to promote fire-resilient construction

I recommend reading the conclusions for yourself.

5 thoughts on “Climate Science Voyage of Discovery: Climate Attribution For Wildfires and the Science-Journalism Translation”

  1. Hi Sharon,

    Just pointing out the fact that I never have shared anything to do with ENSO. In fact, I had to google what ENSO (El Niño Southern Oscillation) even was.

    However, I have shared info and a graph about PDO (Pacific Decadal Oscillation).

    Here’s some quickly-source info on the big the difference between the two: The Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) influence sea surface temperatures, sea level pressure, and surface winds in very similar ways. The most obvious difference between the PDO and ENSO is the time scale. Whereas ENSO events tend to persist on the order of one year, the PDO signature can last up to 30 years (Mantua, 2001).

    If you could please correct your original blog post to reflect the fact that “Matthew’s graphs of ENSO” have never been shared on this blog. Thanks.

  2. Sure there was a drought but human mismanagement of the land (excessive tilling) is what caused the Dust Bowl. This was incented and exacerbated by short-sighted public policy (the Homestead Act of 1862, then the Enlarged Homestead Act of 1909). Seems like a familiar conundrum, huh?

    I highly recommend Timothy Egan’s history of the era, The Worst Hard Time, to anyone who would like to learn more.

    • I read that book also and watched the Ken Burns film (which I recommend), plus I spend time in the area with people who lived through it.

      There are many narratives for that piece of history. The one I would choose is “if you live in places with a history of droughts, you need to develop management practices that work in wet years and dry years- or understand and predict precipitation a heckuva lot more than we did then.”

      Today we have the same (or drier and hotter) climate, many acres of (dryland) wheat farming, and no Dustbowl. I give credit to the SCS and agricultural research and extension.

      Even more interesting, people are now saying raising cattle, in turn, is bad for the environment, and we need to plant more crops (or rewild it, I guess).

  3. Keeley added, “We ought to be much more concerned with ignition sources than a 1- to 2-degree change in temperature.” That sounds a lot more like opinion than facts. I would argue that short-term responses aren’t worth much unless we are equally or more concerned about the long term, and are doing something about it.

    I had to read post this several times to find the point, which I think I found here: “So we can’t go directly to “reducing carbon (alone) will solve the problem.”” Maybe reducing carbon is not sufficient, but it’s hard to argue that it’s not necessary.


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