WUWT by Jim Steele 11/9/2019
As one wildfire expert wrote, “Predicting future fire regimes is not rocket science; it is far more complicated than that.†But regardless of accuracy, most people are attracted to very simple narratives such as: more CO2 causes global warming causes more fires. Accordingly in the summer of 2019, CNN trumpeted the headline California wildfires burn 500% more land because of climate change. They claimed, “the cause of the increase is simple. Hotter temperatures cause drier land, which causes a parched atmosphere.†CNN based their claims on a scientific paper by lead authors Park Williams and John Abatzoglou titled Observed Impacts of Anthropogenic Climate Change on Wildfire in California. The authors are very knowledgeable but appear to have hitched their fame and fortune to pushing a very simple claim that climate change drives bigger wildfires. As will be seen, their advocacy appears to have caused them to stray from objective scientific analyses.
If Williams and Abatzoglou were not so focused on forcing a global warming connection, they would have at least raised the question, ‘why did much bigger fires happen during cooler decades?’ The 1825 New Brunswick fire burned 3,000,000 acres. In Idaho and Montana the Great Fire of 1910 burnt another 3,000,000 acres. In 1871, the Great Michigan Fire burned 2,500,000 acres. Those fires were not only 6 times larger than California’s biggest fire, they occurred in moister regions, regions that don’t experience California’s Mediterranean climate with its guaranteed months of drought each and every summer. If those huge devastating fires occurred in much cooler times, what are the other driving factors of big wildfires?
Bad analyses cause bad remedies, and here is why Williams and Abatzoglou’s last paper exemplifies a bad scientific analysis. Analyzing changes in California’s burned areas from 1972 to 2018 they claimed, “The clearest link between California wildfires and anthropogenic climate change thus far, has been via warming-driven increases in atmospheric aridity, which works to dry fuels and promote summer forest fire.†But natural cycles of low rainfall due to La Niñas also cause dry fuels. The increase in burned area is also attributed to increases in human ignitions such as faulty electrical grids, to increased surface fuels from years of fire suppression, and to changes in vegetation that increased the abundance of easily ignited fine fuels like annual grasses. Furthermore, temperatures in some local regions experiencing the biggest fires have not been warming over the past 50 years (See temperature graphs in this essay’s last segment. Data from Western Regional Climate Center). All those factors promote rapid wildfire spread and greater burned areas. Although good science demands separating those contributing factors before analyzing a possible correlation between temperature and area burned, Williams and Abatzoglou oddly did not do so! That’s bad science.
More:
https://wattsupwiththat.com/2019/11/09/how-bad-science-horrific-journalism-misrepresent-wildfires-and-climate/
