I happened to run across something that contradicts Bob Zybach’s repeated assertions that, “these fires have been clearly predicted by me and others because of USFS management policies and Wilderness designations and have zero to do with warming climate or drier fuels.” The Union of Concerned Scientists calculated the effect of warming climate and drier fuels on burned area, and the result from their peer-reviewed analysis is not “zero.”
Climate change is causing hotter, drier conditions that are also fueling these increasingly large and severe wildfires. In particular, vapor pressure deficit (VPD), a measure of atmospheric “thirst,” has emerged as a key way of tracking how climate change is amplifying wildfires because of its role in regulating water dynamics in ecosystems and, together with rising temperatures, contributing to increasing dryness (Box 1).
UCS used a combination of data and modeling to determine how much the carbon emissions associated with 88 major carbon producers (hereafter, the “big 88”) have historically contributed to increases in VPD and burned forest area across the western United States and southwestern Canada (see Methodology).
Across western North America, the area burned by forest fires increases exponentially as VPD increases, which means that relatively small changes in VPD result in large changes in burned forest area. The observed rise in VPD has enabled a steep increase in the forest area that has burned across the region since the mid-1980s. Since 1986,1 a cumulative 53.0 million acres of forest area has burned across western North America as VPD has risen. Without emissions tied to the big 88, the rise in VPD would have been much smaller, and 33.3 million acres (IQR 27.7 million–38.5 million) would have burned (Figure 4). That means that 37 percent (IQR 26–47 percent) of the cumulative burned forest area from 1986 to 2021 is attributable to emissions from the big 88. This represents nearly 19.8 million acres of burned forest area, or an area roughly the size of Maine.
You can criticize UCS for being agenda-driven (and we’ve talked about the limitations of “burned area” as a metric), but I’d challenge Bob or others to provide a similarly peer-reviewed research paper that attributes fire effects to his chosen causes.