October 02, 2017

Western Washington Summer Smoke: Was 2017 the Smokiest Summer Ever? If so, why?

 This was a smoky summer in western Washington and many people feel it was the worst they ever experienced here in terms of the number of days with serious smoke.

So how unusual was it?  And if it was unusual, then why?  Global warming?  Mismanaged forests?  Unusual weather?  Let's examine this issue in some detail.

My own subjective experience was that this was the smokiest summers I have experienced going back four decades.  A number of folks who have lived here for many years suggested the same thing.   What about objective information?

The Puget Sound Clean Air Agency has measurements of atmospheric particulates (PM 2.5) that go back to 2000. Looking at daily averages at Seattle for that period, one finds that early August 2017 had the highest values for the entire record, and looking closely (click on image to enlarge), you will find that this summer was the smokiest as well.

Or take a look at the monthly averages.  August 2017 was the smokiest of ANY month...even the normally more polluted winter months.  Very impressive.

So for the younger folks around Puget Sound reading this blog, summer 2017 was the smokiest you have experienced.  This is probably true for those of you who have gray hairs.

If ones goes back 100-120 years, there were some smokier summers or at least smokier events.  For example, there was the famous Yacolt Burn, north of the Columbia Gorge, in 1902.  According to historical accounts, the smoke was so thick that street lights glowed at noon in Seattle 160 miles (258 km) away and ships on the Columbia River were forced to navigate by compass.  Much worse than this summer.

But what was it about this summer that made it so smoky? 

From I can discern from the wildfire statistics, we had a big year, but not a record-breaking one (for the past few decades) in terms of acreage of burned area over our region. 2015, for example, had more area burned.

We started the summer quite moist, with the wettest winter/early spring in regional history.   Snowpack was good.   So we began the season in good shape.

But what about the July-August weather and soil moisture conditions?  July-August temperature over WA State was above normal, but no record.
 July-August precipitation was low, but several years were in the same neighborhood.   Besides we typically get little rain anyway.
 And the Palmer Drought Severity Index (negative is bad) showed conditions ere not unusual at all.

So we were warm and dry, but why so much smoke west of the Cascade crest?

We need to dig deeper to explain our smoky summer.  One thing we did have was varied sources of fire.  First, we got smoke from BC, then southern Oregon, and then our homegrown fires on the eastern sides of the Cascades.   I can't remember a year with so many fires, so geographically dispersed, coupled with an early start in BC.

And when the smoke got it in, it didn't leave due to unusually stagnant conditions.

And in fact, the atmospheric circulation over our region WAS anomalous.  As shown by the upper level chart below (which shows the anomalies from normal of 500 hPa heights), we had unusually persistent high pressure over the western U.S. for June through September (red colors).
Such high pressure produces warmer temperatures, less rainfall, and lighter winds.... everything we observed this summer.  And a very strong LOW PRESSURE  area (trough or low) was observed offshore (the purple colors), which weakened he normal eastern Pacific High pressure, that in turn contributes to the onshore flow of clean marine air.

So my take is that the key player in our smoky summer, the progenitor of most of our problems, was the high pressure area (or ridge) that parked itself over the region, coupled with the strong offshore trough.  This combination greatly weakened the onshore flow of clean air that western WA generally enjoys.  It produced stagnation, sinking warm/dry air, and frequent bouts of easterly flow that brought in the smoke.

There is no reason to expect that such high pressure areas have anything to do so human-caused global warming, and climate models actually predict less of them as the earth warms.  But humans have contributed to the wildfire issue, with degraded, highly flammable forests east of the Cascade crest, the legacy of years of mismanagement and fire suppression. Our political leadership have been too slow to deal with our problematic forests.


  1. Cliff: Thank you for your excellent analysis of last summer's smoky conditions through most of the Pacific Northwest, including Seattle.

    You focus on mismanagement of eastside forests as a major contributor, but westside forests are just as much -- if not more -- to blame, particularly for this year. The common factors in these events is that they almost all take place on federal lands and this pattern only started in 1987. From 1951 until 1987 (36 years), in fact, there was only one large-scale forest fire in western Oregon and Washington; in 1966. This year alone there were 10 such fires -- and this pattern is typical for much of the past 30 years. The difference? Passive management of federal lands, just as you describe.

    Another contributing factor, which you mention, was the very wet winter and spring. This leads to massive build-ups of volatile fuels, such as grasses and shrubs. Our dry summers dessicate these growths, providing tons of flash fuels within and adjacent to our forests.

    As I summarized in a recent article I wrote on this topic: "The primary air pollution and public health problems associated with wildfires is not C02, it is smoke."

    Bob Zybach

  2. Good points all, but the fire in the Gorge was caused by an idiot teenager who threw a boatload of lit fireworks down into a deep gorge, until the area finally caught fire and started rapidly burning out of control. Just one more reason to ban fireworks in Washington.

  3. Back in the 70's and 80's the logging companies held "slash burns" every autumn as soon as the first rains moistened the underbrush. There were some very smoky weeks back then, although I don't ever remember ash falling!

  4. All of the above on the smoke issue. The last few days have been very dry. Even with clear night skies there has been no dew. None - that's dry for the Peninsula.

  5. Also, people contributed to the situation by starting the Diamond Creek fire which burned approximately 140,000 acres here in Washington.

  6. The graph seems to indicate one of the least smoky winters preceded it. If so, I wonder what drove that effect.

  7. Bob and Cliff -

    It is heartening to see others begin to speak truth about forest fire management today.

    But imo you are not going far enough on this. Just ask anyone who lived through the Methow or Chelan Valley fires in the last 5 years (we did). What I witnessed was not passive. It was highly aggressive, and it involved torching miles and miles of forest, all under the purpose of lighting "backfires". On perfectly calm days in the middle of the summer, they just methodically went mile to mile lighting the forest.

    Don't believe me? Read some of the books out now. Read "Burned Out", and the first hand descriptions of the people that saw this happen.

    It bothers me Cliff that you have a photo of a forest on fire as part of a "Regional Impacts of Climate Change". You have written multiple blog posts on the lack of evidence for this... and then to also understand how these fires are becoming massive due to management...I don't get it.

    I fully understand that forest health depends on fire, and I do not debate that. My problem is the lack of honesty about what is happening on the ground in our summers today. Comparing acres burned today, or smoke in the air, or any quantifiable measurement - versus the past - is willfully ignoring the night and day difference between objectives.

    There is way more to this, and it gets darker from here. But it is heartening to read others begin to discuss what - to those of us who have experienced it - know first hand: forest fire management today is not remotely reflective of the past.

  8. I just today finished reading "Megafire" by Michael Kodas. He would agree with your conclusion.

  9. You write that "From I can discern from the wildfire statistics, we had a big year, but not a record-breaking one" but perhaps you are just referring to Washington State fires? As you know our largest period of smoke came from fires burning in British Colombia, and this was a record-breaking year for them with over 1.2 million hectares burned.


  10. I don't dispute your personal experience and am not looking to defend the Forest Service (or whomever is suppressing fires), but I do think the shift in how fires are being fought also stems from the increasing encroachment of houses and people onto the forested areas in question. So to have a truthful and accurate discussion we also need to consider how changes to our society's land settlement patterns influences the current stance with fire suppression.


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

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