January 14, 2025

Why the LA Wildfires Have Little to With Drought or Climate Change

Some climate activists and media outlets are claiming the drought or climate change were major contributors to the recent wildfires around Los Angeles (see sample below)

These claims can easily be shown to be false.

Drought had little impact on the LA fires.

Climate Change had little impact.  




Let me provide the facts below.

The Fuels

The vegetative fuels for the fires were predominantly light fuels such as grasses and range vegetation.  To illustrate, consider the area where the Palisades fire started (below).


Most of these fuels are 1-10 hr fuels, which means they typically dry out after 1-10 hours of drying conditions.   

So even if the previous period had been wetter than normal, then a half-day of drying conditions would make them ready to burn.  The meteorological conditions immediately preceding the fires were so drying (very strong winds with  very low humidities) that even if it had rained the week before, the fire still would have occurred.


Consider a plot of the ten-hour fuel moisture at the nearby Topanga Canyon site over the past year (below).  Keep in mind that when the moisture level gets below 15% rapid fire spread is possible.  

Interestingly, even during every wet periods (such as the first part of 2024), fuel moisture levels return to burning-level fuel moisture between showers.




But grasses and bushes were not the only thing that burned.  Once the wildfires got to the homes or burning embers reaches the homes, the homes THEMSELVES supplied the fuels.  

One house ignited the next.   

This is very similar to the situations of others major urban wildfires, such as the Camp Fire (Paradise, CA), Lahaina (Maui), and the Marshal Fire (Superior, CO).   Homes flammability has little to do with weather conditions.   But poorly constructed homes (e.g., flammable roofs, no screens to stop embers moving into home spaces) are major problems.

There is No Trend of Less Precipitation in Southern California

Several media and other outlets suggested climate change associated dry conditions was a contributor to the LA wildfires.   First,  as noted above, the light fuels that brought the fires to the homes did not need a drought period to be sufficiently dried to burn.  

But even if drought had been important, there is no evidence than climate change could have contributed.   How can I be be so sure?  Because there is no long-term trend for less precipitation over the region.

Consider the trends of October 1 to January 6 precipitation at Los Angeles from 1950 through this year (see below).  The trend line is UPWARDS (brown line).   More rain, not less.  Yes, the past autumn was dry, but that is not climate but normal weather variability.

Not convinced?    Below is the annual precipitation of the region since the late 1940s.  

No downward trend.  And the last several years have been wetter than normal, which would contribute to more bountiful vegetative growth and thus more fire potential.

The LA Fires Were Associated with Strong-Dry Santa Ana Winds.  Such winds are predicted to WEAKEN, NOT Strengthen under global warming.

The LA wildfires were associated with very strong (up to 100 mph) and dry Santa Ana winds, which were generally from the northeast.

There is an extensive peer-reviewed science literature indicating that global warming will reduce the strength, intensity, and frequency of such Santa Ana winds.



It makes complete sense that global warming would weaken the Santa Ana winds.  

Such winds are driven by difference in pressure between inland high pressure and lower pressure to the south and west.  This high pressure is associated with low-level cool air (cool air is denser and heavier than warm air), which will be warmed due to global warming, thus reducing the pressure difference that drives the Santa Ana winds.

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Very strong video and photographic evidence indicated the Los Angeles Eaton fire, which resulted in the most deaths was due to a faulty power line.  Clearly, this transmission line was not de-energized even with the forecast of severe Santa Ana winds.






6 comments:

  1. The truth can be difficult to grapple with, so people prefer life experiences be explained away with simple clichés. The climate change cliché provides the easy out.

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  2. Great point Cliff especially on poorly designed homes as it relates fire fire-resistant materials and design. This article highlights that https://headwaterseconomics.org/natural-hazards/wildfire-resistant-costs-california/?utm_source=chatgpt.com

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  3. Ok, so no climate change attribution for how dry it is or the low current humidity. But could you please address the wind speeds observed (both sustained and gusts) and how/if they are related to climate change? Might as well comment on Lahaina if you can at the same time. Anyone older than 40 years old can casually observe that these events seem to be getting worse.

    ReplyDelete
    Replies
    1. 1) per Cliff "There is an extensive peer-reviewed science literature indicating that global warming will reduce the strength, intensity, and frequency of such Santa Ana winds"

      2) Human perception is highly flawed - ie, when you're shopping for a Volkswagen every car seems to be a Volkswagen

      3) Even IF fires are getting worse it could be due to any number of reasons, including fire prevention/management (clearing brush, less logging roads, water management, etc), increased population (as a result of immigration) or any number of other reasons.

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    2. As someone over 40, I can tell you I cannot make that statement. Worse by what means? Actual wind speeds? We cannot just say since we are over 40 we've seen it all. If stating we are seeing more destruction of property and dollar loss, look beyond the weather to answer that question. It's not the fact that things have gotten any worse, it's the fact we are building more in areas that suffer from these events. More people, more houses, more the loss of life and destruction. But again to say a person can observe its getting worse is to assume that you've seen everything mother nature has to offer within our short lives. Cliff has again and again proven our perceived severity of events do not play out in the actual numbers or trends.

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  4. Here’s a story about a local-to-Altadena weather enthusiast who pre-warned the community of the extreme fire danger and helped save a bunch of lives.
    https://www.goodnewsnetwork.org/hundreds-credit-altadena-heros-early-weather-predictions-for-saving-them-from-the-eaton-fire/

    ReplyDelete

Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

Why the LA Wildfires Have Little to With Drought or Climate Change

Some climate activists and media outlets are claiming the drought or climate change were major contributors to the recent wildfires around L...