CALIFORNIA FIRES:MORE CAUSES THAN JUST CLIMATE CHANGE
California is prone to wildfires. The cause of the recent tragic California forest fires which destroyed more than 12,000 homes and incinerated about 150,000 acres of forest (equivalent to ten Manhattan Islands) are a natural consequence of that state’s geography, the type and distribution of natural vegetation, its climate, and most importantly the recent rapid housing and other development in formerly unpopulated forested areas. The element of climate change though a factor is only one many causes.
Wednesday November 21, 2018
Monday of this week was a bit hazy. Weather observers in NYC noted the existence of a high dry haze which created a colorful sunset and was later reported to be a plume of tiny carbon particulates generated by the extensive forest fires in California. The smoke plume was carried eastward over New York and New England by the prevailing upper air winds.
When the topic of California’s forest fires are reported or discussed—the oft repeated watch word seems to be “climate change”. On a visit to the affected areas in California this last week President Trump ( a self described climate change denier) was harangued by Governor Brown repeatedly regarding the presumed cause of the several blazes. Governor Brown emphasized climate alteration as if that was the only cause of the tragedy. Though human climate alteration is no doubt one of the factors—it is not the prime cause.
Wildfires are a natural phenomena in California.
First the geography. California is situated on the US west coast of a mountainous North American continent. Within the state’s eastern boundaries are highlands such as the the Cascade and the Sierra Nevada ranges. In bordering states to the east the Colorado Plateau and the high-dry Basins and Range provinces of Nevada and New Mexico rise up thousands of feet above sea level.
Meteorology and the infamous Santa Ana winds. In the fall of the year cool, dry air often settle in the above described interior highlands, creating a zone of high pressure. Under those conditions any low pressure systems in the Pacific Ocean off the California coast generate an “egg beater effect”. Highs circulate the cool, dry air from the interior highlands toward the off-shore counterclockwise spiraling low pressure center, As these northwesterly winds move over California, they follow the contours of the land moving from high elevations to lower ones near the coast. As they move they undergo a heating process (“compression heating”) caused by their change in elevation and pressure. The air heats up dramatically (@ 5 degrees for every 1000 feet they descend) as a result of increasing atmospheric pressure at lower elevations. (Recall how air pumped when compressed to fill an automobile tire heats up the tire as it is inflated, or the heat generated in the metal walls of a propane tank when it is filled) Such heating is common in the atmosphere and is termed “adiabatic” temperature change. It has That is non-passive heat or heat generated by changes in pressure. But as the air heats its relative humidity drops drastically as well.
As a result of these natural circumstances, California, in the autumn of the year, under Santa Ana winds —is often very much hotter and much drier than the expansive deserts which are found over the Cascades and the Sierra Nevada to the immediate east. Furthermore, as the air descends and flows westward it is forced though several wind gaps in the north-south mountain ranges. In these “gap” areas wind speeds increase dramatically. Speeds may reach gale force levels during times of Santa Anas. That is a wind velocity (@ 40-45 mph) which can break branches off trees and impede walking.
The Climate. California has hot, dry summers and a mild winter. The Koeppen climate classification map for California indicates that the “hot summer Mediterranean” climate zone is the most widely distributed and covers the most extensive area in the state. (This climate type is also found in southern Spain, and Portugal, northern Morocco, the Balearic Islands, Sardinia and Corsica, Sicily, and Greece) In this climate regime temperatures in the coldest months average above freezing. Winters are mild and bring three times more precipitation than the driest months of summer. While summer precipitation is very sparse, being typically less than one inch. These climate conditions: hot, droughty summers and mild relatively moist winters naturally control the type of vegetation which grows in these extensive areas of the state.
The natural vegetation. Over eons of time before man arrived, the process of natural selection and evolution resulted in vegetation types which were naturally adapted for survival in the climate in zones found in the state The natural plant community found in the “hot summer Mediterranean” climatic zone in California is called: chaparral.
Chaparral, (a designation derived from a Spanish word: “chaparro” meaning small or dwarf) is a community of drought and heat resistant low-growing, shrubby, woody, leathery and resinous-leaved evergreen plants These often form dense thickets. The plants are adapted to summer drought, high summer temperatures and infrequent (10 to 15 year interval) wildfires. As they have evolved over thousands of years to resist drought, their physical characteristics of low branching growth (to conserve moisture), and small, evergreen, highly resinous leaves make them also very highly flammable. Wildfires in chaparral explode in intensity. The intense heat from the abundant fuel and winds cause surrounding trees and brush to rapidly and contemporaneously reach its kindling temperature. At that point large areas of vegetation go up in flames at once causing a “fire explosion”. Under certain conditions these fire explosion cause turbulent air to form rising and spiraling columns of fire or: “firenados” which may move over the surface like dust devils or tornadoes.
Population Growth. Forest fires in unpopulated pristine natural areas are rare. Lightning strikes may cause forest fires in ten or fifteen year intervals. But wild fires in recent decades are many more times frequent. In a study of forest fires in Colorado lodgepole pine forests report that in the USA 40% of new homes have been built in the “wild land-urban interface”. These are areas where residential neighborhoods border forest, grasslands or other natural lands. Paradise, California was such a place.. Forest fires are caused most commonly by human actions. Roads, infrastructure and housing developments generate sparks and open fires from auto accidents, fallen power lines, camp fires, or home fires which escape into forested areas and build into conflagrations.
This author is NOT a climate denier! I am well versed in the subject and support the idea that the earth is experiencing human-induced climate alterations...there is no question about that. It is likely that certain aspects of the recurrent and persistent drought that California has experienced has been intensified by climate modification. But that has not been proved by the weather and climatic data available. But to attempt to claim that a slowly altering climate is the PRIMARY cause is a mistake.
Climate change is a cause that we will have only limited ability to control and modulate. And even if we eventually gather up the gumption to make the hard choices to stabilize the levels of greenhouse gases we are dumping in the atmosphere the effects will take multiple generations to have any effect. So those who reside in California must attempt changes which CAN have more immediate effects. There are no quick and certain ways to stem and then reverse climate change. Any efforts in that direction will take decades. But conflagrations in California forests can be more effectively controlled by limiting development and road construction in areas which are naturally prone to fire. Just as coastal and flood plain development in areas prone to flooding is in many states is now limited—so should the natural fire prone forests of California be protected from excessive and dangerous development. Most of the fire prone vegetation zones in California should remain as useful natural areas free from habitations and with only limited access during fire season.
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