http://www.digitaljournal.com/news/environment/going-up-review-of-california-wildfires-since-1984/article/578410

Going up: Review of California wildfires since 1984

Posted Sep 22, 2020 by Tim Sandle
High-severity wildfires in northern coastal California have been increasing, according to new research, by some 10 percent for each decade decade since 1984. This indicates the increased likelihood of wildfires as time passes.
A home burns as flames from the LNU Lightning Complex spread in Vacaville  California on August 19  ...
A home burns as flames from the LNU Lightning Complex spread in Vacaville, California on August 19, 2020
JOSH EDELSON, AFP
As Digital Journal's Karen Graham has reported, landscape-changing wildfires have become a concern worldwide as global warming creates fires that burn more ferociously and more frequently. But how more frequent? A new study from University of California - Davis charts the extent.
According to one of the researchers, Yuhan Huang there is a strong parallel between an increase in fires and climate change, and with wildfires most likely to occur (and be the most severe) under certain conditions. As Huang states: "We found that fires were much bigger and more severe during dry and hot years compared to other climatic conditions."
The research points out that most of the fires occurring now are exacerbated by this heat wave,with the heat wave connected to human activity. This was particularly so for the northwest and southern parts of California, where the severity rating was also greater.
To derive at these outcomes (time and climate), the research group used an advance with machine-learning. The process enabled a model to be constructed and from this real-time predictions to be formed about the likelihood of different levels of fire severity. The one variable that the model requires is a reason for ignition.
Using the machine learning model, the researchers found that 36 percent of fires that occurred between 1984 and 2017 burned at high severity. More specifically, the percentage of high-severity areas doubled, especially during the most recent 2012-2016 drought.
Of interest was the finding that dry years saw a far higher burn severity. In contrast, with wet years, just 20 percent of burns could be classed as high-severity fires (all other wildfires were assessed as burning at a moderate or low severity).
The findings also demonstrated how higher temperature serve to amplify the severity of wildfires. Given the connection with human activities, the researchers state that the research outcomes highlight the importance of controlled land-use planning and fuel management.
The research is published in the journal Environmental Research Letters. The paper is titled "Intensified burn severity in California’s northern coastal mountains by drier climatic condition."