The California Fires Were Not Caused By Climate Change

The following is a guest article by Chris Martz.

To Senator Sanders:

Hi there Colonel Sanders. 

Do you like facts? 

I hope you do, because you’re about to be sacked with some. 

Here we go. . . First, climate change does not cause forest fires. That isn’t how this works. Fires require an ignition source and fuel. 

Ignition sources may be natural (e.g., lightning) or it can be man-made (e.g., by accident from improperly disposed cigarette butts, improperly discarded pellet / wood stove ash, an out-of-control campfire or fallen power lines, or perhaps even intentionally by arson). But, climate change is not one of them.

The origin of the Pacific Palisades fire hasn’t been determined. But, what is known is that it is being fueled by dried out vegetation and is being stoked by Santa Ana Winds (SAWs) with hurricane-force wind gusts. These winds are a byproduct of a tight horizontal pressure gradient between a tropospheric ridge situated over the Great Basin and a cut-off low spinning over Baja California. Southwesterly downslope flow accelerated by a tight gradient can easily dry out vegetation, especially small-diameter fuels like twigs and leaves, priming a forest for a fire should one be ignited.

While the warming atmosphere — and, for sake of argument, we will assume that it is entirely due to mankind’s greenhouse gas (GHG) emissions — might make weather conditions more conducive for forest fires in Southern California, there is yet to be an established “consensus” on exactly how fires will change in the region with increased global warming. The reason for this is because air temperature during the event and precipitation deficits over the preceding weeks and/or months aren’t the only — or necessarily even the most important — factors in fire burn area (e.g., Keeley et al., 2021).

Keeley et al. (2021) found that all SAW-driven fires in Southern California that occurred between 1948 and 2018 had a human ignition source. While the majority between 1948 and 1983 were linked to campfires, arson and powerline failures have been the dominant cause since 1984. These results are similar to those in Balch et al. (2017), which found that 97% of fires in Southern (Mediterranean) California were caused by a human ignition source between 1992 and 2012.

According to Keeley et al. (2021),

The maximum temperature during SAW-driven fires ranged from 42.6-95.4°F (5.9-35.2°C). For January, these values ranged from 44.1-81.1°F (6.7-27.3°C). With a statistical t-test, they found that fires that burned over 1,000 hectares (2,471.05 acres) were not linked to higher-than-average air temperatures, and this also held true for very large fires burning >5,000 hectares (12,355.27 acres). Only 5-20% of the variation in area burned during winter is explained by air temperature.

Precipitation surplus / deficits in the week before a SAW event also did not play a significant role in the incidence and severity of wind-driven fires in the area between 1948 and 2018. This is largely because small-diameter fuels like twigs and leaves will dry out quickly when the weather conditions change.

The study concludes that 75% of SAW events do result in forest fires.

Rather, more human ignitions increase the likelihood that a fire escapes containment and becomes a large destructive fire, regardless of air temperature or soil / fuel moisture conditions both preceding and during a fire event. So, while rising air temperature and lower precipitation can increase fire risk in the future, it is a very small part of the bigger picture.

Keeley et al. (2021) concludes that,

““Future fire losses can be reduced by greater emphasis on maintenance of utility lines and attention to planning urban growth in ways that reduce the potential for powerline ignitions.”

What’s more, it is unclear at this point in time exactly how SAW events will change in response to a warming climate.

One study, Rolinski et al. (2019), has found a recent observational increase in SAW days over the past two decades and links this to increased jet stream ridging patterns in California.

However, Guzman-Morales & Gershunov (2019) finds that a weakening of the southwest pressure gradient that drives these SAWs in their global climate models (GCMs) in response to GHG forcing on the climate system, although the trends are diminished in the late autumn and winter months.

So, there’s quite a bit of uncertainty here.

There is evidence of some influence of GHG forcing on creating a more favorable fire weather environment in Southern California in recent decades.

However, burn area associated with SAW events isn’t very dependent on the air temperature during the fire, and antecedent precipitation and fuel moisture aren’t very critical either. This is because downslope airflow is sufficient enough to dry out most vegetation in just a matter of hours, creating a tinderbox should a forest be set ablaze. And, how SAW evolve with a changing climate is unclear.

But, placing powerlines underground can significantly reduce fire risk in the future, and having better forest management (e.g., controlled burning and mechanical thinning of underbrush) will as well.

Climate change is real, but grifters like Senator Bernie Sanders need to stop pinning every natural disaster that happens on it, and using these crises as a crutch to advance their political agendas. Junk science is bad for policymaking and leads to ineffective solutions to the challenges facing society.

Originally published at Chris Martz Twitter