Are the Recent Northwest Wildfires a Sign of Global Warming? The Science Says No

From the Cliff Mass Weather Blog

Cliff Mass

During the last few weeks, a series of wildfires have occurred over the region.

Today’s satellite imagery shows where the fires were burning (orange dots), with smoke plumes quite evident. Most of these fires began in grass/range vegetation.

In mid-June, there were a few grass/range fires in the Columbia Basin (see image below).

There has been drumbeat in the media that the wildfires were the result of, or significantly enhanced by, global warming/climate change due to increasing greenhouse gases such as CO2.  

For example, a story from the Seattle Times Climate Lab was full of demonstrably false claims (such as claims that wildfires are occurring ahead of schedule due to global warming).

In this blog, I will provide the facts and demonstrate that the global warming connection with the current fires contradicts current scientific understanding.

Fire Ignition

The fires during the first half of summer were either human-initiated or caused by lightning. 

 Human ignition obviously is not related to increasing greenhouse gases, and neither is lightning.   

In fact, I examined this issue with colleagues at the Washington State Climatologist Office, examining the potential for lightning using state-of-the-science regional climate models.

The results were clear: under global warming, there are no increases in lightning activity for Washington State (see sample graphic below for Ross Lake in the WA Cascades)

Mid-summer is the lightning season in the Cascades and eastern Washington, as noted by the lightning climatology below.  Nothing unusual.

In short, we can say definitively that fire initiation in our region has nothing to do with global warming.

The Fuels

Then there are the claims that a lack of snowpack or prematurely dried fuels were important in the fires this summer, with both due to global warming.  This is demonstrably false.

A map of the fires this year (below) shows that nearly all occurred over grass/rangeland or started in grass/rangeland and then spread into terrain.

Because the fires started at lower elevations, the below-normal snowpack of the last year had no impact on these fires.

Even at one higher-elevation fire (Little Giant), the fire started in an open area of a previous burn with lots of grass and downed trees.

A key point is that the range/grass areas were already dry, as would be expected this time of the year, even without any global warming.  

Their moisture content was NEAR NORMAL before the fires.

Want proof?  The US Forest Service summarizes the fuel moisture for various regions of the Northwest (see below)

Consider region 10, which includes many of the fires.  The 100-hour fuel moisture (small vegetation) has been near normal (the gray shaded area), so was the ERC (energy release component) of the fuels.

In summary, any claims that human-caused global warming contributed to the recent Northwest wildfires are demonstrably false.

Lightning ignited fuels of normal dryness.

But there is something that has radically increased the chances of wildfires east of the Cascade crest:  the invasion of highly flammable invasive grasses, such as cheatgrass.  A map of the “exotic” grasses is shown below.   You won’t hear about this in certain media and by some advocacy groups.   But the increase of these grasses during the past half-century has greatly enhanced the flammability of the landscape.