Wine Country Fire October 2017 |
As sure as the winds will blow, climate demagogues hijack
every human tragedy to amplify fears of rising CO2 concentrations. Despite the
fact that other critical factors were the 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 thus 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 prevented 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 load, 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.
Prescribed Control Burn |
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 Abatzoglou 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.
Figure 3 |
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 to Santa Rosa as well as the Santa Annas to
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 Fahrenheit
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 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.
Devastated Neighborhoods in Santa Rosa |
To summarize, none of the
fire components - ignition, fuels, or spread – had been affected by climate
change.
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 and 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 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.