There is an obvious contradiction regarding wildfires and climate in the western United States that few people talk about. The area of forest fires is low, although summers in most regions are warm and dry.
This year has been one of the most benign wildfire years in a long time for the entire West Coast. The graph of California wildfire area since 1987 (see below) shows that the area burned in 2022 is quite low, similar to the situation 30 years ago.
And the same is true for Washington State (below, 2002 to present). The area of forest fire this year is very modest…similar to 20 years ago.
Interestingly, this low-fire zone situation persisted despite the fact that the west coast states experienced warmer and drier weather than usual.
Consider the difference in temperatures this summer (June 1 to October 15) from normal (average 1990-2010) – see below. Warmer than usual for the entire coast! You would expect more fires – right?
What about rainfall and drought? Well, people love watching the NOAA Drought Monitor, whose November 1 graphic shows a terrible drought in California and eastern Oregon, and a mild drought in the rest.
You would think this would encourage intense wildfires!
But it didn’t.
How is this possible?
It turns out that the forest fire happened is much more complicated than the simple relationship between wildfires, temperature and rainfall described in some media and by some politicians.
Confirm this by plotting the average temperature, rainfall, and wildfire area in Washington from 2002 to this year (below).
2022 has the warmest summer (June to October) of the entire period so far.
And this summer is much drier than usual… the driest summer in 15 years!
But the forest fire area is very low ….. again, how is that possible?
The relationship between Wildfires and Weather/Climate is more complex than is often depicted
The link between climate and wildfires is more nuanced than some think. And that means the link between global warming and wildfires is not as definitive as is often claimed.
For example, strong winds are an essential ingredient for starting and spreading wildfires. And strong easterly winds (such as the recent Spark propagation winds near Skykomish) are especially important for wildfires west of topographic barriers in the region.
The absence of strong easterly winds this summer and fall has helped put out the fires this year. And recent research suggests that global warming could REDUCE such winds for the entire West Coast, reducing the likelihood of fires starting and spreading. You won’t hear about that in the Seattle Times.
Most West Coast fires are man-made, with poorly maintained electrical infrastructure being the primary cause. Significant efforts have recently been put in place to prune trees near power lines, harden electrical infrastructure, and shut down power lines when strong winds are forecast. This seems to be helping.
Warmer temperatures and drier conditions do not necessarily increase fire risk significantly. The West Coast has a Mediterranean climate with very dry summers. Even a normal summer allows surface fuels (such as grass and other light vegetation) to dry out enough to ignite. Once you get past the arid threshold, being a little drier makes a little difference.
And there are many other factors that affect wildfire areas besides weather and climate. For example, poor forest management and 75 years of fire suppression have created forests at risk of catastrophic fires. Invasive combustible grasses have increased the risk of fire, as well as increased the likelihood of human ignition. The new “let it burn” directive is increasing the fire. On the other hand, once there is a fire, the area is less likely to burn for a while.
In short, the relationship of a bushfire area to weather or climate is complicated with many other important factors – if not MORE important…. factors other than climate.
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