Global Warming Exacerbates Wildfires
Some background on this article: On September 29th, a confused and stubborn 86-year-old climate-change-denying man (one of the original two who inspired me to write Megan’s Climate Corner back in June) submitted a letter to editor that was so piss-poor in its climate and fire science comprehension, that it doesn’t deserve to be re-published. Especially not here. The letter writer claimed, “Wildfires are not getting worse and global warming causes greening of the Earth.” These blatantly wrong conclusions provoked me to write a retort. My response was as follows:
Greetings, readers! Let’s debunk some poppycock and balderdash!
Let’s recap a few key concepts. First, global warming does NOT cause wildfires, it exacerbates them. ‘Exacerbates means ‘to make worse’. Only an ignition source like lightning or a spark of anthropogenic origins can cause a wildfire. As the atmosphere, oceans, and landmasses warm, the hydrological cycle becomes more energetic. Evaporation increases in some places while other areas receive record-breaking rainfall and floods.
Second, the American West is aridifying, which is different from drought. Evapotraspiration (the movement of water from vegetation and soil into the atmosphere) will, in the long term (over decades), vastly outpace precipitation, thus altering this local ecosystem to become more drought-adapted. Oaks and scrubby shrubs will dominate this Northern California landscape in the future. If we’re lucky.
Third, the Wintu people burned this landscape every single year for thousands of years. They managed the forests better than we do today. We’ve allowed fuels to build up in the understory, and that means there’s more energy available for fires. Although the number of fires in the USA shows a slight downward trend in the last 30 years, overall acreage shows a slight increase (https://crsreports.congress.gov/product/pdf/IF/IF10244). Megafires didn’t exist before now because the fuels were never this dense. This is more a result of direct human mismanagement, rather than a strict byproduct of global warming.
Fourth, the “greening” of Earth observed since the 1990s is largely due to reforestation and conservation efforts in India and China (https://www.nasa.gov/feature/ames/human-activity-in-china-and-india-dominates-the-greening-of-earth-nasa-study-shows/). We will talk more about this momentarily.
Mr. Jeans (hereafter referred to as ‘LW’ for ‘letter writer’) slightly misrepresented reality in his September 29th submission. Let’s deep dive into the paper he cited: ‘Spatial and Temporal Patterns of Global Burned Area in Response to Anthropogenic and Environmental Factors: Reconstructing Global Fire History for the 20th and Early 21st Centuries.’
“Fire regimes are largely regulated by climate [Morton et al., 2013] and human activities [Marlon et al., 2008]; meanwhile, burning of biomass can speed up climate change through altering atmospheric radiative characteristics and land surface albedo [Andreae, 1991; Langmann et al., 2009; Levine et al., 1995; Randerson et al., 2006; Y. Liu et al., 2013].”
This means that humans have used fire to clear forested landscapes for crops and livestock for millennia. When a forest has been cleared, this results in a higher albedo. Albedo is the shininess of an object, and Earth actually bounces light back out into space just like the other planets we observe in the sky. Without dark, heat-absorbing forests dominating Earth’s surface, light-colored soil can bounce light and heat back out into space. At the same time, wildfires release MASSIVE amount of CO2 into the air, thus exacerbating the positive feedback loop of warming.
“In the future, the global fire regimes may be quite different from the present pattern due to rapid climate change [Bowman et al., 2009], and anthropogenic effects on fire might become less important than climatic influences [Pechony and Shindell, 2010].”
Again, the fact that we have had fires in the past doesn’t really matter. The last time carbon dioxide concentrations were this high (409 parts per million) was THREE million years ago (https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide). Humans have only existed for two million years. The tight link, the positive correlation between carbon dioxide and warming, has been scientifically proven since the 1850s thanks to the unsung chemical work completed by Eunice Foote (https://physicstoday.scitation.org/do/10.1063/PT.6.4.20210823a/full/).
We are careening toward temperatures we may not be biologically capable of surviving. (We might be able to adapt with the assistance of technology like air conditioning . . . for a time).
The study LW cited uses something called ‘process-based fire modeling’ to enter many variables (relative humidity, aboveground biomass, fires spread rate, etc.) into a computer model to then compare to old, charred, carbon-dated biomass. It’s a tricky objective, and these estimates are significantly less precise than our modern-day satellite imagery and data.
In the authors’ own words: “Model simulated fire patterns are not often consistent with each other. For example, Kloster et al. [2010] estimated global fire patterns based on the modified CTEM-Fire model and found a declining trend in burned areas from the 1900s to the 1960s and an increasing trend from the 1970s to the 1990s. However, the estimation by Li et al. [2013] based on CLM-Fire model presented a declining trend from the 1870s to the 1990s.”
The 1870s to 1890s was a time of great industrialization. Much of the forest was intentionally cleared away for timber, the development of large residential units, and for agriculture. Fewer trees, fewer fires.
Global warming does not cause “significant greening of the earth.” Greening can only be accomplished with sufficient water. In contrast, the West is browning up due to aridification. Rather, global warming increases the length of the growing season by warming earlier in the year and delaying the first frost of autumn later in the year. As previously mentioned, the reason we have observed overall greening since the 1990s via satellite imagery is due to India and China planting more trees. My alma mater Boston University led the study! Read about it here: https://www.bu.edu/articles/2019/humans-are-officially-greening-the-earth-is-that-a-good-thing/.
“In the western United States, wildfire frequency has increased since the mid-1980s in response to the climate warming and extended fire season [Westerling et al., 2006].” It is well-understood that fires are growing larger, more severe, and more destructive with massive acreage as the fire season lengthens. Maybe as our forests burn away, we will have fewer megafires. Our trees are burning faster than they are regrowing. And of course, we are increasingly short on water: tree mortality by desiccation and beetle damage are also on the rise.
“It isn’t true that facts never change minds. They just don’t change minds that are already made up. If you see your ideas as identities to defend, you twist and resist data to rationalize your views. If you treat ideas as a hunch to test, you embrace data to update your views.” Adam Grant.
LW cited an article that uses imprecise methods for past fire reconstruction and cherry-picked the ONLY two sentences that supported his false claim, “Wildfires are not worsening.” Dude, they totally are.
Indigenous elders used to consider potential environmental, ecological, and cultural impacts seven generations down the line. Our society refuses to consider the welfare of even the presently living and breathing. I face insults and slander quite regularly for writing this article, but I’m doing it because I know for a fact that I have former students in the seventh, eighth, and ninth grades reading it.
Those kids need to hear a voice roar for them, they need to see someone going to bat for their right to exist on a habitable planet. I cry often, because I feel that elders like LW are actively opposed to the welfare of everyone currently in existence, and everyone yet to come. Then I wipe my tears away, and put my fingers to the keyboard.
Next time, we’ll debunk Mr. Jeans’ claim that ‘because ice ages used to occur, this extremely rapid, planet-wide heating can’t possibly be caused by humans.’ Or some illogical balderdash. At long last, we’ll learn about the Milankovitch Cycles and how they drove the ice ages to a steady rhythm for the last two million years. Stay tuned.
