From Watts Up With That?
By Jim Steele
In their Goss et al (2020) paper Climate Change Is Increasing the Likelihood of Extreme Autumn Wildfire Conditions Across California, those alarmist scientists clearly stated their intention was to make climate change the culprit by presenting an investigation that “only considers changes in climatic contributions to wildfire risk, irrespective of changes in fire ignitions, vegetation, land use or management strategies.” However, all those other factors can completely account for wildfire trends unrelated to climate change. For example, while much research has shown human ignitions have tripled the length of fire season, alarmist scientists dishonestly push a narrative that it is climate warming trends that have extended fire season. Papers not accounting for all confounding factors affecting a narrative, should never pass peer review. It is advocacy, not science! So, lets learn some science.
History shows that despite cooler and moister conditions pre-1800, an estimated ~4.5 million acres burned annually in California during the Little Ice Age (Stephens 2007). This far exceeds a 1979–1988 average of ~337,000 burnt acres/year, which then recently increased to a 21st century average of ~708,000 acres/year. However, California’s August 2020 fires did reach a similar burnt area of 4.4 million acres, when a rare swarm of thousands of dry lightning strikes ignited several small fires. Understanding the importance of vegetation analyses, reveals the great majority of lightning fires begin by igniting “fine fuels” like dead grasses, which then produce the fastest moving fires and burn the greatest area. Despite alarmists’ claims the recent increased burnt area is an indicator of climate change, vegetation changes are far more important. Burnt area is mostly determined by the presence and continuity of “fine fuels” and strong winds. But there were not any unusually strong winds when those 2020 fires began. But there has been an increase in invasive annual grasses creating greater fuel abunadance and continuity. For example, fine fuels (invasive annual grasses) have increased more than eightfold from 1990 to 2020 in the Great Basin which includes most of Nevada, half of Utah, and 10-20% of California, enabling a greater burnt area.
Understand The Critical Role of Fine Fuels
“Fine Fuels” are defined as dead vegetation less than ¼ inch in diameter. This includes cured grasses, weeds, pine needles, fallen leaves, and the small twigs of shrubs. They are also classified by fire experts as 1-hour fuels because they gain and lose moisture extremely quickly, gaining or losing 63% of their moisture in just 1 hour. Fine fuels can become highly flammable in just 60 minutes after a light rain. Climate change is totally irrelevant for fine fuel dryness and flammability.
Accordingly, 90+% of all wildfire ignitions happen in easily ignited fine fuels. Depending on the winds a grass fire, as seen in graphic A, will then rapidly spread the fire by advancing about 1 foot/second. The fire will keep advancing as long as flammable fuels are present near the flame front. However, a road may prevent the extent of grass fires, which partially explains why roadless areas experience the worst fires. Furthermore, statistics suggesting an increase in forest wildfires, obscure the fact that typically ~90–97% of the forest floor area in Sierra Nevada forests/woodlands is covered by 1-hour and 10-hour fine fuels. A grass fire’s flame front does not remain in one position for more than 5 to 15 seconds, so it moves rapidly through the forest floor without killing trees which require much more heat for a much longer time (graphic B).
However, if the fires are carried into the forests where poor land management has allowed shrubs and young trees and fine fuels to increase, the undergrowth provides ground fuels and enough fuels to release ample heat that can ignite ladder fuels and torch trees to create crown fires that emit embers that then spread the fire rapidly through the air. (graphic C & D)
Understand The Critical Role of Heat Source
Fine fuels require a heat flux (minimum rate of energy input) of 8,000–16,000 W/m² for several seconds. Higher fluxes ignite fine fuels more quickly. The flame front of an advancing grass fire releases 20,000–50,000 W/m², and that amount of heat easily dries and ignites 1-hour and 10-hour fuels, but not enough heat to burn live trees or dead logs with diameters greater than 3 inches. Multiple embers released by torched trees often collect on roofs with average heat fluxes of 15,000–80,000 W/m². Those heat sources are enough to ignite your house.
For heat flux comparisons, the sun provides at most about 1,000 W/m² of energy onto the earth’s surface on a clear day at noon. CO2’s current concentration adds less than 2.5 W/m² of energy since the Little Ice Age. However, a standard match provides about 25,000 W/m², but only for about 15 seconds. So, an arson’s match easily ignites any fine fuels and starts a wildfire. Depending on the electric current strength and other factors, a downed power line can produce 10,000 to 600,000 W/m² for several seconds to minutes. Thus, many major fires have been ignited when sparking electrical lines ignited the surrounding fine fuels. Although lightning can deliver up to a billion W/m², it only does so for less than a second. Such a short heat pulse rarely ignites a tree so primarily limits lightning’s wildfire ignitions to fine fuels.
Understand The Critical Role of Dryness
Flammability is high for most woody fuels when moisture content falls below 30%. Firewood is generally considered ready to burn efficiently below ~20–25% moisture content. Under 60% relative humidity, fine fuels commonly reach 10–20% flammable moisture content at air temperatures ranging from 30–100°F (–1 to 38°C). In contrast to claims by alarmist scientists, 1.5°C of global warming adds meaningless drying relative to the range of natural temperature fluctuations.
For example, during the rainless summer in California’s Mediterranean climate, relative humidity naturally falls and dries fine fuel’s moisture content to below 10% every day. Consider in California’s inland valleys and foothills during August, high relative humidity of 60% to 75% typically happens in the morning with temperatures in the 50s to mid-60s°F (10–19°C). Despite those cool temperatures, fine fuel moisture content reaches a very flammable 12% to 15%. As temperatures warm in the afternoon, commonly to the 80s and 90s°F (27–37°C), relative humidity falls to 30%-40%, drying fine fuels to a highly flammable 6-8% moisture content. More amazing, during the colder fall and winter temperatures when Santa Ana and Diablo wind events occur, the dry air descending from the deserts often lowers relative humidity to just 2%. Below ~10% moisture content, ignition probability from a single spark or discarded burning cigarette becomes extremely high. This evidence partially explains why despite 1.5°C cooler average temperatures during the Little Ice Age, 4.5 million acres had still burned annually in California.
To prevent rotting from fungi, exterior wood and building materials for houses range from 9% to 14% moisture content causing your house to burn more efficiently than dry firewood. Thus, we often observe neighborhoods burnt to the ground in a wildfire despite being surrounded by living trees with unaffected leaves and needles (graphic E in Paradise Camp fire and graphic F in the Dixie fire).
How to Protect Your Home from Wildfire
While so-called climate experts obfuscate wildfire science and claim you can reduce the threat of wildfire by reducing fossil fuel use, NOTHING could be further from the truth. Sadly, too many people have been lulled into wrongly thinking they are protecting their homes by buying electric vehicles or not eating meat. These obfuscating climate alarmists encourage people to stop critical thinking about how to honestly deal with wildfire threats, while useful idiots in social media advocate meaningless actions like eating bugs instead of beef.
To protect your home, simply prevent fine fuels and embers from carrying the fire into your flammable home. Create a defensible perimeter at least 5 meters away from your home by removing any fine fuels and any flammable vegetation. Don’t store flammable materials next to your home. Remove any tree branches overhanging your home and remove all low hanging branches that would provide der fuels that produce canopy fires and wind carried embers. Install fire resistant roofing and screens over all vents where embers could enter. If you understand the science of how wildfires spread, these precautions are just common sense. Alarmist climate experts be damned. Once you install these precautions, you can then guiltlessly enjoy a hamburger and fossil fuel powered heating and cooling systems.
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