USA — Ongoing climate change will likely add three weeks to the fire season by 2050, according to several new studies.
Fires burn 90,000 acres more each year
Wildfires in the West have grown steadily larger and more frequent over the past 30 years and projected increases in average temperatures and drought will keep the alarming trend going, according to a study published in the Geophysical Research Letters. The average area burned has increased by an astonishing 90,000 acres annually based on satellite data, concluded the researchers.
The scientists linked the rise to observed increases in temperature, setting the odds that climate change isnt driving the upsurge at less than 1 percent. Most of the areas seeing the biggest upsurge in fires also were suffering from drought.
They also concluded that the actual fire patterns closely matched the predictions of the major climate models when they plugged in the actual measurements over the past 30 years. That gives extra confidence in the predictions of the climate models for the future.
The increase in fire frequency and severity was most pronounced in Arizona, New Mexico, the Rocky Mountains, the southern plains, eastern Colorado, southwestern California and western Texas.
Humans caused fire deficit
Another study by researchers from Northern Arizona University came to similar conclusions.
Professor Scott Anderson concluded that grazing and strenuous fire suppression efforts significantly reduced the number of fires in the West for a century, but that allowed huge amounts of dead and downed wood to build up on the forest floor.
As a result, forest managers created what amounted to a fire deficit, which accounts for the rush of flames to make up for the delay exacerbated by rising average temperatures and a near-record drought.
Most fire in 3,000 years
The same conclusion emerged from a study that used tree rings and other evidence to estimate fire frequency going back some 3,000 years. Researchers from the National Science Foundation, Montana State University, the University of Oregon and elsewhere published the study in the National Academy of Sciences.
They found wildfires actually peaked in the 1800s in the American West, then dropped drastically in the 20th century as a result of the settlement. Cattle grazed off the grass that once carried frequent, low-intensity fires and active suppression of those that started led to the buildup of fuels.
Key conclusions included:
Warm periods like the Medieval Climate Anomaly between 1,000 and 700 years ago saw a significant increase in the number and extent of fires compared to cool, wet periods like the Little Ice Age between 500 and 300 years ago shortly after people like the Mogollon and Hohokam abandoned civilizations that had lasted for 1,000 years.
Wildfires during the 20th century declined to a frequency not seen since the Little Ice Age 400 years ago. Human-caused changes like grazing and fire suppression caused fires to shift from a 1,000-year maximum to a 1,000-year minimum in just a century.
The researchers concluded that the warming trend has now caused bigger and more frequent wildfires than any period in the past 3,000 years, including the striking Medieval Climate Anomaly.
Warming impact by region
Another study by scientists at the Harvard School of Engineering and Applied Sciences concluded wildfires in the West would generate twice as much smoke on average and burn a much larger area as a consequence.
Publishing in the journal Atmospheric Environment, the researchers concluded that even if rising temperatures cause more storms and evaporation and puts more moisture in the air in the Western United States temperature alone seems to play the leading role in wildfire patterns.
Still, each region had different patterns.
In the Rocky Mountains, moisture on the forest floor had the biggest influence, which therefore has to do with rainfall and snowpack.
However, in the Great Basin, with its brush and stunted growth, dry fuel left over from the previous growing season plays the leading role. Therefore, in the Great Basin, a wet year that promotes the growth of brush and grass followed by a dry year will produce the biggest fires.
The researchers then used computer models that predict future temperature increases as greenhouse gases accumulate in the atmosphere to come up with some estimates about the change in fire behavior in the West between now and 2050.
They concluded that the number of megafires like the Wallow Fire would increase 200 to 300 percent. The total area burned annually will probably double. And the fire season will start in late April instead of early May and extend all the way until mid October instead of early October.
The fire season in Rim Country has already started this year about a month earlier than last year and six to eight weeks sooner than in many years past.
Total smoke produced should increase by between 20 percent and 100 percent. Thats ironic, since the smoke from the fires produced by the increased carbon dioxide in the atmosphere will therefore pump more carbon dioxide into the atmosphere.
Smoke poses health risk
As it happens, another recent study predicts smoke from a big increase in wildfires will pose health risks for humans.
The study published in the American Chemical Societys Environmental Science and Technology journal concluded that emissions from wildfires in California would grow by 19 to 101 percent by 2100. The extra smoke will degrade air quality and aggravate respiratory conditions, decrease crop yields and affect forest health.