Guest essay by Jim Steele
Director emeritus Sierra Nevada Field Campus, San Francisco State University and author of Landscapes & Cycles: An Environmentalist’s Journey to Climate Skepticism
As sure as the winds will blow, climate demagogues hijack every human tragedy to amplify fears of rising CO2 concentrations. Despite that fact other critical factors were keys to understanding the devastation of the Wine Country fires, politicians like Hillary Clinton, Al Gore and Governor Jerry Brown were quick to proclaim climate change had made the fires worse than they would have been.
Climate researcher Kevin Trenberth has long tried to undermine the foundations of science by discarding the null hypothesis. Without formal testing whether a tornado, hurricane or wildfire event is within the expectations of natural variability, Trenberth simply asserts every tragedy is made worse by rising CO2. Accordingly, he is interviewed by climate change propagandists after every weather tragedy. In an interview with InsideClimateNews a few months before the Wine Country wildfires Trenberth continued to proselytize his views, “Whatever conditions exists, they’re always exacerbated by climate change. There’s always that heat variable, the increased risk.”
Indeed heat is always a variable, but usually it has nothing to do with CO2. Sadly, due to his extreme beliefs Trenberth often confuses climate with weather.
Similarly, Daniel Swain who authors a good California Weather Blog, unfortunately strays when he tries to interject CO2-climate change into an otherwise good weather analysis. Writing the fires should also be looked at from “the long-term climate context,” he argued the “record-hottest summer” dried out the vegetation exacerbating the fire conditions. But he too failed to separate natural climate and weather events from his hypothesized contributions from CO2. As will become clear from a more detailed analysis, climate change played no part in the wildfire devastation.
The Ignition Component
Fire danger rating systems analyze 1) an ignition component, 2) a fuel component and 3) a spread component to determine how to allocate fire-fighting resources and when to issue public alerts. Natural fires are caused by lightning, and so good weather models can forecast the short-term probability of lightning fires. Lightning fires are also more likely during warm and moist seasons enhancing their window of predictability. Unfortunately, Cal Fire reports 95% of California fires are unpredictably ignited by humans.
Climate alarmists like Dr. Trenberth have blithely suggested global warming is increasing the fire season stating, “In the West, they used to talk about a fire season, the fire season used to be 60 days, then 90 days, and now they think it’s year-round. There’s no pause.” Tragically that uncritical belief in a climate-related extended fire season has been parroted by lay person and scientists alike. But the facts show the observed extended fire season is due to human ignitions. Blaming climate change is fake news!
In a 2017 paper researchers reported that across the USA from 1992 to 2012, “human-caused fire season was three times longer than the lightning-caused fire season and added an average of 40,000 wildfires per year across the United States. Human-started wildfires disproportionally occurred where fuel moisture was higher.” Furthermore “Human-started wildfires were dominant (>80% of ignitions) in over 5.1 million km2, the vast majority of the United States, whereas lightning-started fires were dominant in only 0.7 million km2.”
We can reduce some human caused ignitions. The Wine Country fires were not ignited by lightning but all observations suggest they were started by downed power lines in high winds. A year ago, California legislators introduced a bipartisan bill aimed at reducing wildfire ignitions from powerlines. Although governor Brown hypes the unsubstantiated dangers of climate change, he vetoed the bill which would have promoted real action to prevent well-known human causes of wildfires. Preventing powerline ignition could have prevent the Wine Country tragedy.
The Fuel Component
Fire ecologist will estimate a fire’s potential intensity by calculating the Energy Release Component (ERC), a measure of the potential heat energy per square foot. ERC is a function of the biomass both dead and alive, and the biomass moisture content. As fuels increase and as fuels dry the ERC increases. Live fuels are modeled such that maximum moisture content coincides with the peak growing season, and declines thereafter as the plants go dormant. Moisture content of dead fuels are modeled according to their diameters.
Depending on their diameters, dead fuels will lose moisture as they equilibrate with their dry surroundings at rates that vary from 1 hour to 1000 hours or more. To aid in firefighting management decisions, fuels are categorized into 4 groups as described in Gaining an Understanding of the National Fire Danger Rating System published by the National Wildfire Coordinating Group
1-Hour Time-lag Fuels “consist of herbaceous plants or round wood less than one-quarter inch in diameter. Also included is the uppermost layer of litter on the forest floor.” The ERC of these fuels and thus the fire danger, can change throughout the day. Dead grass as well as twigs and small stems of chaparral shrubs are 1-hour fuels, and those fine fuels sustained the rapid spread of the Wine Country fires. Assertions that recent and past summer droughts or decades of climate change had dried the fuels and exacerbated the Wine Country fire danger have absolutely no scientific basis. The approach of the hot, bone-dry Diablo Winds would have extracted all the possible moisture from the dead grasses and chaparral twigs within hours, regardless of past temperatures. Trenberth and Swain simply confused rapid weather changes with climate change.
The critical “long-term context” they never discussed is that a century of fire suppression allowed destructive levels of fuel loads to develop, increasing the biomass component of the ERC estimate. As populations grew, so did the demand to suppress every small fire that could threaten a building. Natural small fires reduce the fuel lad, whereas fire suppression allows fast drying fuels to accumulate. Unfortunately, fire suppression only delays the inevitable while stocking more fuel for a much more intense blaze. Local officials and preservationists have long been aware of this problem, and controlled burns to reduce those fuels were being increasingly prescribed. Tragically, it was too little too late.
Figure 1: A prescribed control burn in Wine Country
10-Hour Time-lag Fuels are “dead fuels consisting of round wood in the size range of one quarter to one inch in diameter and, very roughly, the layer of litter extending from just below the surface to three-quarters of an inch below the surface.” The fuel moisture of these fuels vary from day to day and modeled moisture content is based on length of day, cloud cover or solar radiation, temperature and relative humidity.
100-Hour Time-lag Fuels are “dead fuels consisting of round wood in the size range of 1 to 3 inches in diameter and, very roughly, the forest floor from three quarters of an inch to four inches below the surface.” Moisture content of these fuels are also a function of length of day (as influenced by latitude and calendar date), maximum and minimum temperature and relative humidity, and precipitation duration in the previous 24 hours.
Much of the chaparral shrubs produce twigs and stems in size ranges of the 1-hr, 10-hr and 100-hr fuels. These fuels were most likely the source of burning embers that high winds propelled into the devastated residential areas. Again, these dried out fuels are the result of a natural California summer drought and short term weather conditions such as the bone-dry Diablo Winds that arrive every year.
Figure 2 Moisture content of 3-8 inch diameter fuels from March to December
1000-Hour Time-lag Fuels are “dead fuels consisting of round wood 3 to 8 inches in diameter or the layer of the forest floor more than about four inches below the surface or both”. These larger fuels are more sensitive to drought conditions that existed months earlier, so it could be rightfully argued that a hotter drier July and August made these fuels more flammable in October and exacerbated the fires.
Fire ecologists planning prescribed burns to reduce fuel loads, wait until the 1000-Hr fuels’ moisture content is reduced to 12% or lower. If these larger fuels are dry, it is certain the smaller fuel categories are dry as well, so that all fuels will be highly flammable. As seen in the graph above (Figure 2) 1000-hr fuels reach that critical dryness threshold by July 1st and remain below that threshold until mid-October when the rains begin to return. Contrary to Trenberth’s blather, California’s fire season has always lasted 90+ days. Undoubtedly the unusually hot and dry 2017 summer would have lowered 1000-hr fuel moisture content even further. Nonetheless those fuels become naturally flammable every summer. Furthermore, these larger fuels were less often burned and thus insignificant factors regards the fires rapid spread. The rapid spread of the fires was due to consumption of the rapidly drying fuels.
Swain is fond of finding a “record setting” metric to bolster his climate change assertions. As such, he noted the “record-hot summer had dried out vegetation to record levels” and linked to a graph tweeted by John Badoglio showing October ERC values for the past 30 years were at a record high in 2017 (in part because of delayed rains). However, that “record” was also largely irrelevant. The ERC calculation is heavily biased by the greater biomass of the larger 1000-hr fuels that would indeed get drier as the autumn continued without rain. Still those larger fuels were insignificant contributors to the rapidly spreading fire. As seen below (Figure 3), the grasses have been entirely burnt while the larger shrubs and trees, as well as the woody debris near the base of the trees (in the upper left) have not been consumed. In fact many of the trees are still alive. The potential energy estimated by the “record ERC” was only partially realized. It was the fast-drying dead grass and chaparral shrubs that turned potential ERC into meaningful fiery heat.
The Spread Component
“The spread component is defined as “the theoretical ideal rate of spread expressed in feet-
per-minute.” Wind speed, slope and fine fuel moisture are key inputs in the calculation of the spread component, thus accounting for a high variability from day-to-day.” Thus, a combination of dry fuels and high winds typically result in fire-watch and red-flag warnings one day and no warnings days later as the winds subside. Forest rangers are well aware that September and October bring the powerful Diablo Winds of Santa Rosa as well as the Santa Annas of southern California, and with those winds comes the highest fire danger.
Cliff Mass is an atmospheric scientist at the University of Washington and author of the superb Cliff Mass Weather and Climate blogs. An October 16th post provides an excellent summary of the metorological conditions that created the fierce winds driving the Wine Country fires. In essence, a strong approaching wind flow (the Diablo Winds) coupled with a thermal inversion near the top of the mountains that border the Santa Rosa valley, accelerated winds into a 60 to 90 mile per hour downslope wind event, a phenomenon known as a mountain wave. Those high winds snapped power line poles and ignited fires. The regional topography also funneled the winds and fire down the valley, taking dead aim at the heart of Santa Rosa. The topography had guided a similar fire in 1964, the Hanley fire, which was started by a carelessly discarded cigarette. Unfortunately without much concern, most of the burnt homes in the Tubbs fire had been built on top of the burnt grounds of that previous Hanley fire, despite public protests.
Were those high winds perhaps exacerbated by climate change? Highly unlikely!
The Diablo Winds affecting Santa Rosa or the Santa Annas of southern California are driven by cooling seasonal temperatures in the high deserts to the east. The inner continent cools faster than the oceans, setting up a pressure gradient driving the winds toward the coast. The winds then heat adiabatically rising 5 degrees Celsius for every 1000 feet of elevation descent. An adiabatic rise in temperature means no added heat from any source and basic physics tells us temperatures can rise adiabatically simply due to compression. Thus an air mass that originated near Flagstaff Arizona at a 6900 foot elevation, could adiabatically warm by 30 degrees as it reaches sea level.
The flow direction of winds are largely driven by unequal seasonal changes in temperatures. During the summer the interior heats faster than the oceans, such that a cooling onshore wind reduces interior temperatures. This pattern reverses in the autumn as the interior lands cool faster than the ocean creating an inland high pressure that drives the Diablo and Santa Anna winds toward the coast. Despite declining solar insolation, this autmn wind flow causes coastal California to experience some of its hottest days of the year in September and October, commonly referred to as Indian summer. Similarly a pressure system that inhibited the cooling onshore winds around San Francisco, resulted in a record hot summer temperature. By simultaneously opposing cooling sea breezes while bringing warm winds that were adiabatically 5 to 10 degrees warmer, temperatures rise and relative humidity falls. The result is bone-dry hot Diablo winds that suck the moisture from land and vegetation where ever the winds pass.
To restate the forces driving the winds, the Diablo winds are the result of a pressure gradient resulting from an interior that cools cooler faster than the ocean. If CO2 is warming the earth to any significant extent, then we would expect that warming to prevent the inner continent from cooling as quickly as it did decades ago. Thus CO2-global warming would predict a decline in that presure gradient and a weakening of these winds.
To summarize, none of the fire components- ignition, fuels, or spread – had been affected by climate changes.
Finally, keen observers will notice that entire blocks of houses, and entire neighborhoods were completely burnt to the ground, in contrast to neighborhood trees that often remained relatively unscathed. This suggests that the high winds rapidly carried burning embers from the grassland and chaparral into these developments. While the trees did not trap the embers, the buildings did. I would expect we will soon hear about investigations inquiring into why these residences were not required to erect more fire safe structures, especially when built in a known fire-prone habitat in a high wind corridor. The simple requirement of constructing eaves in such a manner that prevents the trapping of burning embers and fire-proof roofs may have saved many homes.
Indeed there are many lessons that will allow us to prevent such a wildfire disasters in the future if we have accurately determined the causes of these fires. Cliff Mass notes that our short-term weather models had accurately predicted the time and place of the fiercest winds. That information could be used to temporarily shut down the electrical grid where power lines are likely to ignite fires. We can bury power lines below ground. We can remove the high fuels loads that accumulated during a century of misguided fire suppression. Insurance companies can demand higher rates unless proven precautions are undertaken. It is those lessons that Gore, Clinton, Brown should be promoting to inform the public. Trenberth and Swain should be informing the people of the natural weather dangers that are inevitable. There is no evidence that climate change, whether natural or anthropogenic, exacerbated the ignition, fuels or spread components of these deadly fires. And worse their obsessed belief that rising CO2 concentrations worsen every tragedy only distracts our focus from real life-saving solutions.
Jim Steele is author of Landscapes & Cycles: An Environmentalist’s Journey to Climate Skepticism