Christopher Neely here, grateful for the rain some of the county experienced last night into this morning, and crossing my fingers that we can make it through the end of the year without news of a local wildfire.
Unfortunately, it sometimes feels like that is what it has come to—crossing our fingers, hoping human superstition can outmatch the increased fire risks created by human-caused warming. Of course, there is more we can do to keep fires in check once they’re ignited, such as clearing brush and managing our forests. But as far as our ability to minimize wildfire weather conditions, that ship has sailed for now and any impact we can muster moving forward probably won’t be noticeable for years, if at all.
The relationship between human-caused climate change and increased wildfire risk has been reported ad nauseam. However, a new study led by UCLA researchers clarifies the impact modern society has had on wildfire conditions with an actual number. In the study, published today in the journal Proceedings of the National Academy of Sciences, the researchers use observational analysis and existing climate models to track the human impact on vapor pressure deficit (essentially: the difference between how much moisture the air can carry and how much it is actually carrying) over the last several decades, a metric they cited as the “leading meteorologic variable that controls wildfires” and a “robust, physically meaningful proxy for wildfire risk.” Although it’s not the only variable that contributes to wildfire risk, the impact is clear: the larger the deficit in vapor pressure the greater the wildfire risk.
Human-caused warming is responsible for 68 to 88 percent of the increased vapor pressure deficit trend seen in the western U.S. between 1979 to 2020, according to the researchers. The observational analysis used by the researchers in the study showed that natural causes were responsible for about 32 percent of the increased vapor pressure deficit over that time, leaving 68 percent to be “likely due to anthropogenic warming.” Existing climate models showed that humans were responsible for about 88 percent of the vapor pressure deficit trend, leading the researchers to deduce a range for the human impact.
“Our results suggest that the [western U.S.] appears to have passed a critical threshold and that the dominant control on the fire weather variation in the [western U.S.] has changed from natural climate variability to anthropogenically forced warming,” the study concludes. “The trend toward increasing risk will likely continue over the [western U.S.] ...This change in risk requires urgent and effective societal adaptation and mitigation responses.”
A more accessible statistic, though no easier to swallow, is the total acres burned in the western U.S. over that same time period. According to the study, between 1984 and 2000, 1.69 million acres burned in the region, compared to 3.35 million acres between 2001 and 2018. Both pale in comparison to the 8.8 million acres burned in 2020 alone.
What will “urgent and effective societal adaptation and mitigation responses” look like? California and the rest of the west are figuring that out. In this week’s print edition of the Weekly (which will be on newsstands on Thursday), I write about a controlled burn experiment that took place at the Santa Lucia Preserve in Carmel Valley—an ancient land management and fire control tactic that modern society has gotten away from. It may take multiple forms of ancient wisdom and environmental consciousness to deal with our current reality. Leadership from the government would also help. Let’s cross our fingers that COP26 is more than just talk this year.