Virtually every spring, some media and activists claim that the upcoming summer will bring above-normal wildfire activity over the Pacific Northwest because of global warming/climate change (see example from last year below).
The Seattle Times Climate Lab consistently predicts above-normal fire risks
So what does real data actually say? That will be the topic of this blog.Let's start with actual wildfire information: the total wildfire acreage over Washington State's WA DNR (Department of Natural Resources) lands for the last decade (see below).
You will note no upward trend. Also note that the last few "drought" years have had below normal wildfire area.
If we compare the Washington State wildfire area against temperature or precipitation across the state, you will note a poor correspondence (see below). Clearly, other elements (e.g., fuel availability, wind, lightning, human ignition) are important as well.
So what about this summer?
An important supporting element for fire is the availability of surface dry fuels (e.g., dry grasses), and there is a website (the U.S. Department of Agriculture's Fuelcast website) that has this information.
The image below shows the latest on the availability of surface fuels such as grasses and flammable vegetation (yellow is below average and green above average).
Lower than normal over much of eastern Washington but above normal over the Cascades, including its eastern slopes.
So good news for the lowlands of eastern Washington and the western slopes of the Cascades. A cause for concern over the upper eastern Cascade slopes...where there was lots of vegetative production by the bountiful precipitation this year.
The latest European Center seasonal precipitation forecasts are a mixed bag. For April/May/June, predicts drier than normal conditions over western Washington and the Cascades, fostering a drying of vegetation and surface debris.
On the other hand, it is predicted to be wetter than normal conditions for the critical July to September period when most of our fires occur.
For temperature, the EC prediction is for warmer-than-normal temperatures (see below), which contributes to drying.
But as shown earlier, temperature and precipitation are only part of the story for local wildfires.
Lightning is critical, particularly since it often ignites fire in remote areas.
Strong winds are essential for the biggest fires, contributing to ignition and rapidly spreading the flames.
Human ignition is important, and that depends in part on the willingness of utilities to maintain lines and de-energize when advisable.
Fuel availability is significant, and we have a good idea now of the vulnerable areas (eastern slopes of the Cascades).
To put it concisely, a simple argument that global warming causes more fires is simplistic and generally wrong, and a more nuanced and data-driven analysis is critical.
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Like in Lake Wobegon where all kids are above average - ST headlines are all above normal.
ReplyDeleteSo why is your wildfire acreage data limited to WA DNR lands? That's only a fraction of wildfire acreage in the state.
ReplyDeletethat plot was easily accessible but total acres would certainly be similar. Let me pull that together for a future blog.
DeleteState DNR says 85 percent of destructive wildfires here are caused by human activity. Last year's Bear Creek fire in the Olympic range is an example. As our population has and continues to increase it would seem that ignition will continue to rise with increasing activity outdoors.
ReplyDeleteThe graph you have of area burned only shows area burned over DNR’s fire protection area, which includes non-federal undeveloped forestlands. Fires on federal lands (like Forest Service lands) would add a lot of acreage to that graph and I feel like the graph is misleading unless you also include that acreage.
ReplyDeleteI question some of your comments about recent fire activity in Washington. First, your graph of acres burned do not include burned acres in federal lands. This for example would omit the large fires of last summer along the Cascade east slopes which burned mostly in federal lands, but also acres burned in other previous recent years. Also the time period you use for comparison, just the last 10 years, is not representative of the longer term average, as this recent period contained several large fire years. A longer term average covering the years back into the 1900s (but not including the early 1900s before serious fire suppression began) would show a much lower average annual loss. Secondly, although acres burned is correlated with warm temperatures and lack of precipitation, it is much better correlated to those conditions which occur during the late spring and summer and not, as your graphs cover, on an annual basis.
ReplyDeleteThe amount of burned acres for a season is nearly always determined by weather and fuel conditions in Eastern Washington since that is usually where the largest loss occurs, and the nature of our summer time lightning storms often determines this. Wind of course is factor but the large fires in Eastern Washington are mostly driven eastward by westerly winds which, unlike the east winds of Western Washington, are a common occurrence during the summers in Eastern Washington. It is the combination of extended warm, dry periods followed by dry lightning storms that usually lead to the large losses east of that Cascades. Maybe climate change has not been a factor in our recent more serious fire seasons, but it is true that an increasing number of our recent summers of this century have been hotter and drier than those in the prior century.
Of the reasons given, only "Human ignition" can be ameliorated by humans. Over many years we have more people, more homes and cabins in rural areas, more varied and longer recreational activities, and lots of invasive grasses.
ReplyDeleteSome of the 85% of fires are caused by such things as - -
Debris or ditch and field burning, Equipment and vehicle use,
Guns and explosives, Smoking discards,
Fireworks, Railroad operations, Electric fences,
Recreation (includes campfires), Power generation/transmission/distribution,
Arson, Anything that can cause a spark
Continue: There has always been a "Spring-Dip" (a dip in foliar moisture content) in last year's vegetation -- even while there is the appearance of lush greenery. This is known to be important in pine tree crown fire activity. Just because they are called "evergreen" doesn't mean the needles don't die, dry, and burn. Likewise for grass.
ReplyDeleteAll I can say about the Seattle Times information is that even a broken clock is right twice a day.
ReplyDeleteIn those areas that are vulnerable to "lightning strike ignition" (I don't know where that's likely): Have any experiments been conducted employing lightning-rods? I'm not suggesting that strategy as-much as "I'm just curious"!! As for the stupidity, ignorance, and laziness of people - well... The Smokey Bear "Only you can prevent forest fires" has a lot of merit.
ReplyDeleteWhile there is short-term variations the long-term trend is a rising one which will most likely continue. There is a strong correlation between increasing fuel loads and acreage burned and virtually no correlation between the modest increase in temperature and acres burned since the late 1970s in the U.S. I've been reading "Indians, Fire and the Land of the Pacific Northwest" by Robert Boyd. It appears we are in unchartered territory regarding fuel load. His works documents the burning practices of the indigenous peoples prior to late 1700s. They were masters at manipulating the environment to meet their needs using fire. They did this for millenia, burning very frequently, but because of the frequency, the fires were much less intense. The forests of today are much denser and cover more of the landscape resulting in much increase fire probabilty.
ReplyDeleteCliff, I was wondering if you read the study reported in the April 17, 2026 issue of Science Advances, regarding the increase in recent years of night time burning conditions in forest areas of the US and Canada. The study states that due to increasing hours in more recent years of warmer and drier conditions at night due to climate change, that fires are now burning longer and hotter into the night time hours. They repeat the observation that night temperatures are warming faster than day time temperatures, one of the predictions made by climate scientists.
ReplyDeleteYes... I read it. The problem with this paper and others like it is that correlation does not mean causation.... a problem for many of the wildfire/climate papers. There have been massive changes on the ground (e.g. fuels), forest management, and ignition sources (rapidly increasing), so pinning the blame on a modest warming is not very rigorous..cliff
DeleteThanks for the article.
ReplyDeleteThe lack of a consistent upward trend in recent wildfire data is an important insight.
Professor Mass, the temperature anomalies, that’s summer temperatures; correct? And is that from the ECMF? I ask because the temperature shows between 0 to 1 degree above the average. Looks less alarming than what the Weather Channel is predicting.
ReplyDelete