Probably the most fearsome of the weather extremes commonly blamed on human-caused climate change are tornadoes – the previous topic in this series – and wildfires. Both can arrive with little or no warning, making it difficult or impossible to flee, are often deadly, and typically destroy hundreds of homes and other structures. But just like tornadoes, there is no scientific evidence that the frequency or severity of wildfires are on the rise in a warming world.
You wouldn’t know that, however, from the mass hysteria generated by the mainstream media and climate activists almost every time a wildfire breaks out, especially in naturally dry climates such as those in California, Australia or Spain. While it’s true that the number of acres burned annually in the U.S. has gone up over the last 20 years or so, the present burned area is still only a small fraction of what it was back in the record 1930s, as seen in the figure below, showing data compiled by the U.S. National Interagency Fire Center.
Because modern global warming was barely underway in the 1930s, climate change clearly has nothing to do with the incineration of U.S. forests. Exactly the same trend is apparent in the next figure, which depicts the estimated area worldwide burned by wildfires, by decade from 1900 to 2010. Clearly, wildfires have diminished globally as the planet has warmed.
Global Burned Area
In the Mediterranean, although the annual number of wildfires has more than doubled since 1980, the burned area over three decades has mimicked the global trend and declined:
Mediterranean Wildfire Occurrence & Burnt Area
The contrast between the Mediterranean and the U.S., where wildfires are becoming fewer but larger in area, has been attributed to different forest management policies on the two sides of the Atlantic – despite the protestations of U.S. politicians and firefighting officials in western states that climate change is responsible for the uptick in fire size. The next figure illustrates the timeline from 1600 onwards of fire occurrence at more than 800 different sites in western North America.
Western North America Wildfire Occurrence
The sudden drop in wildfire occurrence around 1880 has been ascribed to the expansion of American livestock grazing in order to feed a rapidly growing population. Intensive sheep and cattle grazing after that time consumed most of the grasses that previously constituted the fuel for wildfires. This depletion of fuel, together with the firebreaks created by the constant movement of herds back and forth to water sources, and by the arrival of railroads, drastically reduced the incidence of wildfires. And once mechanical equipment for firefighting such as fire engines and aircraft became available in the 20th century, more and more emphasis was placed on wildfire prevention.
But wildfire suppression in the U.S. has led to considerable increases in forest density and the buildup of undergrowth, both of which greatly enhance the potential for bigger and sometimes hotter fires – the latter characterized by a growing number of terrifying, superhot “firenadoes” or fire whirls occasionally observed in today’s wildfires.
Intentional burning, long used by native tribes and early settlers and even advocated by some environmentalists who point out that fire is in fact a natural part of forest ecology as seen in the preceding figure, has become a thing of the past. Only now, after several devastating wildfires in California, is the idea of controlled burning being revived in the U.S. In Europe, on the other hand, prescribed burning has been supported by land managers for many years.
Combined with overgrowth, global warming does play a role by drying out vegetation and forests more rapidly than before. But there’s no evidence at all for the notion peddled by the media that climate change has amplified the impact of fires on the ecosystem, known technically as fire severity. Indeed, at least 10 published studies of forest fires in the western U.S. have found no recent trend in increasing fire severity.
You may think that the ever-rising level of CO2 in the atmosphere would exacerbate wildfire risk, since CO2 promotes plant growth. But at the same time, higher CO2 levels reduce plant transpiration, meaning that plants’ stomata or breathing pores open less, the leaves lose less water and more moisture is retained in the soil. Increased soil moisture has led to a worldwide greening of the planet.
In summary, the mistaken belief that the “new normal” of devastating wildfires around the globe is a result of climate change is not supported by the evidence. Humans, nevertheless, are the primary reason that wildfires have become larger and more destructive today. Population growth has caused more people to build in fire-prone areas, where fires are frequently sparked by an aging network of power lines and other electrical equipment. Coupled with poor forest management, this constitutes a recipe for disaster.
Next: No Evidence That Climate Change Causes Weather Extremes: (6) Heat Waves