The main problem that I have with this thread is the title. There may be no or little correlation between climate change and many wildfire occurring in the Far Western U.S. during this year and
other years but there is no way to conclude that there is No Correlation Between Climate Change And Wildfires In California – Or Anywhere Else On Earth. There are many factors that influence wildfire activity
that makes analysis of the causes difficult. Some of what I have read here regarding the lack of correlation between wildfires in coastal California and Oregon in the year 2017 and 2020 is persuasive, but there are counter
arguments by many other scientists that point to human influence.
This is from Carbon Brief
https://www.carbonbrief.org/explainer-how-climate-change-is-affecting-wildfires-around-the-world
Among the research analysed are several “attribution” studies. “Attribution” refers to a fast-growing field of climate science that aims to quantify the “fingerprint” of climate change on extreme-weather events, such as wildfires, heatwaves and floods. (Both Otto and Kirchmeier-Young’s studies are examples of attribution, for example.)
Analysis by Carbon Brief finds that, by the end of 2019, there had been 11 studies published that look into the role of climate change in single wildfire events. Out of these studies, 10 conclude that the fires analysed were made more likely or more severe by climate change.
However, it is worth noting that all of these studies were carried out in either North America or Australia – with, again, no research looking into the role of climate change in fire hotspots, such as central Africa or southeast Asia.
One reason why few wildfire attribution studies have been carried out is that fire risk is affected by multiple meteorological factors, says Kirchmeier-Young.
These include temperature and rainfall, but also wind speed, which can influence the pace at which fires can spread, and soil moisture, which can influence the size of wildfires.
With so many different factors to consider, it can make it difficult to come up with a study framework that encompasses the whole picture of how climate change is affecting the probability and severity of a fire event, she says:“Attribution generally requires you to define the event that you’re looking at. With a heatwave, you may look at maximum temperatures over a particular area, which you can easily get from a climate model. But with fire, there are a lot more variables that come into play – such as temperatures, precipitation levels, wind speed – and that can be a little more challenging.”
The complicated mix of factors affecting fire risk can also make it more difficult to source data, particularly in developing world regions, adds Otto:“You can’t really do an attribution study if you don’t have decent observations. For fire, things like wind and soil moisture are also important, and in many parts of the world you have absolutely no observations for those variables.”
This is from the American Geophysical Union.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019EF001210#eft2577-bib-0100.
Observed Impacts of Anthropogenic Climate Change on Wildfire in California
Abstract
Recent fire seasons have fueled intense speculation regarding the effect of anthropogenic climate change on wildfire in western North America and especially in California. During 1972–2018, California experienced a fivefold increase in annual burned area, mainly due to more than an eightfold increase in summer forest‐fire extent. Increased summer forest‐fire area very likely occurred due to increased atmospheric aridity caused by warming. Since the early 1970s, warm‐season days warmed by approximately 1.4 °C as part of a centennial warming trend, significantly increasing the atmospheric vapor pressure deficit (VPD). These trends are consistent with anthropogenic trends simulated by climate models. The response of summer forest‐fire area to VPD is exponential, meaning that warming has grown increasingly impactful. Robust interannual relationships between VPD and summer forest‐fire area strongly suggest that nearly all of the increase in summer forest‐fire area during 1972–2018 was driven by increased VPD. Climate change effects on summer wildfire were less evident in nonforested lands. In fall, wind events and delayed onset of winter precipitation are the dominant promoters of wildfire. While these variables did not change much over the past century, background warming and consequent fuel drying is increasingly enhancing the potential for large fall wildfires. Among the many processes important to California's diverse fire regimes, warming‐driven fuel drying is the clearest link between anthropogenic climate change and increased California wildfire activity to date.
In this study we evaluated the various possible links between anthropogenic climate change and observed changes in California wildfire activity across seasons, regions, and land cover types since the early 1970s. The clearest link between California wildfire 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, particularly in the North Coast and Sierra Nevada regions. Warming has been far less influential on summer wildfire in nonforest areas. In fall, the drivers of wildfire are particularly complex, but warming does appear to enhance the probability of large fall wildfires such as those in 2017 and 2018, and this effect is likely to grow in the coming decades.
Importantly, the effects of anthropogenic warming on California wildfire thus far have arisen from what may someday be viewed as a relatively small amount of warming. According to climate models, anthropogenic warming since the late 1800s has increased the atmospheric vapor‐pressure deficit by approximately 10%, and this increase is projected to double by the 2060s. Given the exponential response of California burned area to aridity, the influence of anthropogenic warming on wildfire activity over the next few decades will likely be larger than the observed influence thus far where fuel abundance is not limiting.