October 21, 2022

Was Global Warming Behind the Recent Smoky Period in Western Washington?

Some media outlets and activists have been making big claims that the recent westside wildfires and resultant smoke were the result of global warming (also known as "climate change").  

This is simply not true and this blog will provide the evidence.  You decide.

Imagine if you were a journalist assigned to write a story on the potential connection between global warming and westside wildfires.   You would certainly want to ask these questions:

1.   Is the area burned west of the Cascade crest increasing over time?   If global warming was the cause one would expect a trend towards more westside wildfires over the past few decades when warming has been greatest.

2.   Are the meteorological factors associated with westside fires trending up over the past decades?   Furthermore, do climate model projections indicate increases over time in these key parameters?    

In the case of westside fires, the key parameter is strong easterly (from the east) winds.   All major westside fires are associated with such winds.   Another (secondary) factor is a dry late summer and autumn, the season of virtually all westside fires.

The Yacolt Burn in 1902 was the most extensive westside fire during the past 120 years.

Responsible journalists and climate activists should be asking and answering these questions.  And it turns out that the best answers to these questions indicate strongly that global warming is not and will not enhance such westside wildfire events.

Let's look at the facts.  

Is there a trend in westside wildfires?

Below is a plot of the burned acreage west of the Cascade crest in Washington.  There were BIG fires early in the 20th century (Yacolt, 1902; Dole Valley, 1929).   Then there was virtually nothing until the much smaller 1951 Olympic Peninsula Fire.  Then another fire "drought" until another small fire in the Olympics (the 2015 Paradise fire),  followed the modest fires of this year.

Do you see evidence of a trend towards more westside fires in Washington?     I don't.  And that alone is enough to deflate any claims of greenhouse warming revving up westside fires.

The Essential Meteorological Requirments for Westside Fires

Westside forests are generally not prone to large fires.   The reasons are evident: these are relatively moist environments, experiencing huge precipitation totals on the windward slopes during the cool season.  They are characterized by a green, moist canopy.    

The period from June to September has little rain in a normal year and there is a slow drying of the surface during the summer, as well as the melting of the snowpack at middle and higher elevations. During the summer there is that generally onshore flow from off the Pacific that keeps temperatures moderate and the air relatively moist.  An inhospitable environment for westside fire.

During most of the summer and fall, the air flooding western Washington is cool and moist.

As long as the flow is westerly (from the west) there is little chance of major westside wildfires. Thus, the ESSENTIAL ingredient for westside fires is to have STRONG easterly winds.

Repeat that statement 3 times.  It is that important.

Easterly winds encourage western wildfires in several ways. First, it replaces the cool, moist ocean air with very dry, warm air from east of the Cascade crest.   Relative humidities can decline from 50-80% to under 10%.  Dry conditions are good for fire, helping to rapidly dry surface fuels--which makes them much more flammable.

Second, as the easterly flow descends the western slopes of the Cascades it is warmed by compression, driving humidity even lower.  Very warm, dry air on the slopes enhances fire potential.

Third, strong winds can provide more oxygen to fires (which they need) and can blow hot embers ahead of the fires, enabling them to spread more quickly.

Fourth, strong easterly winds can START fires, such as by downing powerlines or pushing branches onto powerlines.

I have a National Science Foundation project to look at westside wildfires in Washington and northern Oregon and I (and my students) have studied EVERY large westside fire.   EVERY ONE OF THEM was associated with strong easterly winds.

With this key knowledge in mind, what will global warming do to strong easterly winds in our region?

The answer: global warming (a.k.a. climate change) will WEAKEN the easterly winds, working AGAINST more fires.

To reach this conclusion, we have applied an ensemble of many regional, high-resolution climate simulations.   As illustrated by the figure below (which is from a peer-reviewed paper), increasing greenhouse gases (like CO2) result in weaker easterly winds (in this case near the crest of the central Washington Cascades).
Number of days with strong easterly winds from 1970 to 2100, based on high-resolution climate model projections

The reduction of strong easterly winds with global warming makes total sense physically. 

Global warming preferentially warms the interior of the continent compared to the slow-to-warm coastal zone.    Warming contributes to preferential pressure declines over the interior.   Strong easterly flow is associated with higher pressure over the interior compared to the coast, and thus the preferential warming in the interior WEAKENS the easterly flow.

So the best science, from modeling to physical reasoning, indicates that wildfire-driving easterly flow WEAKENS under climate change.  The opposite of the suggestions in the Seattle Times and elsewhere.

Are Autumns Getting Drier?

    Although easterly winds are the critical requirement for westside wildfires, dry conditions are clearly helpful.  Westside wildfires have occurred during periods of normal precipitation when the easterly flow was sufficiently strong and sustained, but prior dry conditions shorten the period required to dry the surface fuels.    This year was extraordinarily dry--the driest summer/early fall on record-- and this allowed the strong easterly winds of last week to quickly enhance preexisting fires and initiate new ones.

 So let's get to the essential question:  is late summer/early fall precipitation declining on the western slopes of the Cascades and in western Washington in general? 

The answer is NO.  

Here is a plot of August to October precipitation for the last century for the western slopes of the Cascades (and eastern slopes of the Olympics) taken from NOAA Climate Division dataset.  There is no long-term drying--if anything precipitation is going up a bit.  Plotting other areas or individual stations in western Washington produces the same upward trend.

What do climate models project for the future of autumn precipitation as the Earth warms?  As shown below, an INCREASE in precipitation.

The Bottom Line

In contrast to the claims of the Seattle Times and some activist types, there is no reason to expect future increases in the size or frequencies of westside wildfires.  There is no observed upward trend in wildfire acreage west of the Cascade crest.  Global warming should weaken strong easterly flow, the key meteorological factor associated with autumn westside wildfires.   Furthermore, there is no evidence for decreased autumn precipitation over the region and climate models suggest that such precipitation should, in fact, increase.


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  1. Including the early 20th century fires ignores the radical change in USFS fire suppression tactics starting in 1935, and increased fire fighting abilities since then.

  2. You could just about make any story based on those ensemble graphics. If the individual models include an expression of error I doubt that any alleged trend could be supported.

  3. Thank you, Cliff, for continuing to be a voice of sanity as the herd acts like, well, a herd.

    Other factors missed by The Times: logged lands, "working" forests and "restored" (thinned) forests all burn much easier than natural forests. They lack cool shady canopies, and dry out much faster than natural forests, exposed as they are to sun and wind. Sadly, we have very few natural forests left.

    Also, roads are strongly correlated with fire ignitions. Lightning does start fires, but most are caused by people who drive in and just cannot imagine camping without a cheering fire.

    Not so many years ago, land management agencies had patrol men and women, boots on the ground, out there doing what they could to keep fires from being started. Nowadays they are very few, but millions are spent on the "fire industrial complex," paying for insanely expensive aerial water bomber airplanes which do little or nothing to stop blazes. Like the old saw "p***ing on a forest fire."

  4. I think an important factor that you haven't taken in to account here is increasing monsoonal moisture over the mountains, increasing lightning strikes, which is the other critical ingredient to westside fires. In fact, no ignition, it doesn't matter how hot, dry, or windy it is. Lightning frequency coupled with strong east winds is the key here. If monsoonal thunderstorms had not started the Cedar Creek Fire in Oregon, there wouldn't have been a mega west side fire in the state even with the east wind event. I would like to see the trend of lightning strikes in the cascades over the decades.
    Also, what about the increase in speed of drying vegetation with increasing summer nighttime temperatures associated with the enhanced monsoonal humidity?

    1. "In fact, no ignition, it doesn't matter how hot, dry, or windy it is."


    2. I get what they're saying. The idea being that if there is no ignition source to get a fire started then fuel dryness, wind, etc are not themselves going to start a fire. It made enough sense given the context provided by the rest of post.

  5. What WILL enhance West side fires are MORE people, which through statistical probability will produce more morons acting moronically during fire season. More careless camp fires, lit cigarettes out windows etc. That and more people taking up residence at the boundary of the natural and man made world. Climate change will probably make this area even more appealing, unless we totally ignore our power grid...so the fire risk from climate change might go up in proportion to how many people move here....in a very far reaching indirect way.

    1. yep, when I lived outside of Aspen the locals knew full well that even taking a vehicle into dry grasslands at 8,000 above sea level was courting disaster. Cat. coverters on any vehicle can ignite a bonfire.

  6. I think the issue here with much of the public is not more fires, but more smoke in recent years. We have had smokier summers over all of the Pacific Northwest in more recent summers compared to recent past summers. As you have stated, we likely had smokier summers many years ago but nobody here was living during those summers and they only compare our recent summers with those they remember from the recent past. The west side may not get more fires in coming years but a lot of the smoke has been blowing in from fires to the north, east and south of the state and these may likely continue to be a problem.

    1. well.. the smoke is from fires. And the close-in fires produce the worst smoke. Smoke from distant fires tend to remain aloft, with less impact on air quality

  7. Your "Westside Washington Wildfire Acreage" is either missing this year's fires, or 2020's large westside fires (hard to tell with where you've placed the dot).

    It's also missing:
    - 2021 Pincer Creek and Bear Creek fires
    - 2018 Maple fire in the Olympics
    - 2015 Goodell Fire
    - 2003 Mineral Park Fire

    All of these would probably be large enough to show up on your graph, but for some reason they are omitted. Why don't you show a graph of the last 30-50 years that omits the large outliers at the beginning of the 1900s, and with correct data this time?

    1. Lefty....my graph was just for Washington State. Oregon is similar except for the huge 2020 fires, which were driven by record-breaking, unequalled easterly winds. I don't think we can neglect the fires of the early 20th century....they are real and reveal the situation before suppression...cliff

    2. Those fires were all in Washington. Off the top of my head the Pincer and Bear fires were around 1k acres each and Goodell was about 8k. Also Downey Creek was 2.5k in 2020. It's also a quibble on which side of the crest you'd like to "assign" it to but there was also the Norse Peak fire a few years ago.

      The parallel that I see is that 30 years ago some of those fires would have been considered to be medium to large is they occurred on the east side of the Cascades. Now a 5k acre is about the equivalent of a mouse fart.

    3. I wasn't talking about Oregon. Washington had large (for the west side) fires in 2020 also.
      Downey Creek Fire (2,570 acres): https://inciweb.nwcg.gov/incident/7190/
      Big Hollow Fire: no longer an inciweb page for this, but it was at least 18,000 acres.

    4. Some other fires that appear to be missing from this analysis:

      in the Olympics:
      * 2009 - Heat wave complex
      * 2010 - hopper
      * 2011 - Big Hump
      * 2016 - Hayes Two and GodKIN
      * 2016 - Ignar Creek

      in the Cascades:
      * 2009 - Langille
      * 2009 - Moon Complex
      * 2009 - Gold Hill Complex
      * 2015 - Jumbo
      * 2015 - Upper Skagit Complex
      * 2016 - Proctor Creek
      * 2018 - Little Fork
      * 2020 - Big Hollow
      Since my source only goes back to about 2000, I would assume that the data cited in this blog from before then is similarly incomplete.

    5. can you provide the acreage and location of these fires. I suspect most are quite small.

    6. Sadly my GIS-fu is somewhat lacking, so I put this list together by visual inspection. That said, all of these are at least visually in a similar order of magnitude with the paradise fire in the Olympics and several (especially the ones up near Skagit and the Chilliwack) rival the scale of the Bolt Creek fire. I used a premium version of CalTopo as my resource. It appears that they source their data from NIFC here: https://data-nifc.opendata.arcgis.com/datasets/historic-geomac-perimeters-all-years-2000-2018-gdb/about

  8. I don't recall a period of protracted period of smoke around here before 2010 or so.

    Anyway, all three of the fires west of the Cascade crest were human-caused. Punishment for irresponsible or wreckless burning needs to better reflect the economic, public health, and human toll created by wildfires.

    1. The Suiattle River, Boulder Lake, Chilliwack Complex, Murphy Lake and McAllister Creek fires were caused by lightning. Together these have burned more acres than the largest well-known fire (Bolt Creek).

    2. I thnk there are some problems with your information. The NWCC does not show lightning as the cause of the Suiattle firel In any case, fires are caused by lighting and human intervention, with human ignitions totally dominating..

    3. NWCG says the cause of the Suiattle River Fire is "lightning-natural".

  9. Why do you not account for mean temperature in an analysis of wild fire patterns? Wouldn't this be a key element - ie temperature, precipitation, wind, and forest management/fire suppression? This seems like a glaring omission in your assessment. I think that many people are struck by the wildfire smoke more than the actual amount of acreage burned in western WA, but hasn't there been a large uptick in wildfire smoke in western WA in the last few years? Growing up in the south Puget Sound, I don't remember smoke like we frequently have now - but this is more anecdotal.

    The August 2022 mean temp at Seatac was 70.0 F - the 2nd highest on record behind that of August 2017. The September 2022 mean temp at Seatac was 64.8 F, the 2nd highest on record behind September of 2020. These years 2017 and 2020 had noted wildfire activity which seem correlated high mean temperatures at the end of the summer.

    The last decade has seen an increase in mean temperatures reported at Seatac. Is this part of an understanding of wildfire activity, along with precipitation and wind? From 2013-2022, the mean August temperature was 68.95 F, compared to 66.23 F from 2003-2012 and 65.49 F from 1993-2002. Wouldn't the temperature at Seatac would be correlated with higher temperatures in the interior of the state, where wildfire activity is more likely?

    Doesn't the fact that we have seen higher summertime temperatures affect wildfire activity? Living in the Spokane area, we have seen much higher summer mean temperatures. August mean temperatures in Spokane, according to NOAA, have been above 70 F since 2011, a striking difference from all previous recorded data. August 2022 had a mean temp of 76.0 F, highest on record by a wide margin.

    Obviously, reporters frequently oversell, oversimplify and misconstrue all sorts of content, and I don't dispute that claims about climate change are frequently unsupported, but in this case, shouldn't you be factoring in a striking rise in temperatures that we have seen in the last few years?

    1. Temperature actually does not correlate with wildfire well. Interestingly, wildfires in the west are often associated with normal or colder than normal temperatures, since cool air in the interior enhances inland high pressure that produces the critical easterly flow. That said, the west has warmed by roughly 2F over the past fifty years, which could contribute slightly to enhanced summer drying. But that is a secondary effect.

    2. Cooler temperatures are usually present over Eastern Washington when summertime high pressure areas develop east of the Cascades leading to strong easterly winds and increased fire threat west of the Cascades. However, Eastern Washington fires are very well correlated with warmer than average temperatures and the majority of the large fires east of the Cascades have occurred with or shortly following heat spells.

    3. You will always be correct in that global warming is not to blame for our local weather woes. You can statistically show that easterly winds are decreasing but how many days of these winds are needed to fuel a fire. If the number of easterly wind days during the critical time period is greater than 1 we are still surely at danger for increasing wild fires

  10. I measured 0.14" of rain at my house in Bellingham today. The high temperature was 50.7F - the lowest since 4/14/22

  11. I liked your laser focus on important wind is historically to our Precious Northwest. Looking back in time to predict the weather is a mistake. I know that is all the models are, and they are powerful but mostly wrong still. To state unequivicolly that there is only one possible answer...is limiting, and not noticing 1/3 of Pakistan underwater at one point. One of these monester storms will collide with more southern moisture and the Mississippi will indeed become mighty and rewrite the Midwest again. There is more energy, l3ss glacial refraction and ground covered it water ow. 50 years ago doesn't really matter when it can rain 15 inches in a few hours with a storm surge sucked from the sound.
    It has been said that we are now moving into a new dryer environment with less snowpack, less runoff in spring, but kuch worse water drainage issues in fall, winter, and possibly spring. Adjust your data sets, these weekly events are not outliers.

  12. 36.3F overnight at my house in Bellingham - the coldest reading since 4/20/22.

  13. At the Murray vs Smiley senator debates tonight Patty Murray stated that climate change is to blame for the wildfires in Washington State and was going to use that as a basis for action in wildfire prevention in the future.

    Cliff, what's your experience with politicians muddying the water around the facts of climate change, global warming, and our local/state natural events (i.e. wild fires, etc)?

    1. Neither of them spoke well on climate change issues. Kind of disappointing.

  14. Part of the problem with including data from early in the 20th Century is the land management practices have changed significantly. Yacolt in 1902 and the Forks fire in 1951 undoubtedly burned under strong east winds, but they were not burning in pristine forests. They both burned in heavily harvested forests at a time when logging slash was generally left on the ground to rot. Old growth stands produce hundreds of tons of slash that was unmerchantable at that time frame, so there were vast areas in both fires with hundreds of tons of slash on the ground providing a continuous and readily available fuel source. Current practices require this slash be taken care of with either piling and burning, increased utilization, or isolating the slash. Combine that with fact that the vast majority of timber harvest today are conducted in second growth stands which do not have the same amount of biomass as old growth did, and you end up with orders of magnitude less slash on the ground than back in 1902, 1951, or even 1985. All of which makes comparing fire activity from 30-120 years ago an exercise in apples vs. oranges.

    1. You are right about forest practices, and particularly about slash. The big west side fires in the 19th century did include some pristine forests, but more recent fires in the west have often included a substantial slash component....like the westside fires this summer. But in many ways that makes my point stronger..... things we have done on the ground..like big, flammable slash piles... have made the problem worse, making claims of a global warming origin more tenuous.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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