There are major fires burning in and around the Los Angeles metro area this week, causing tragic loss of life and property.
What are the primary drivers of these events and their consequences? What is the impact of climate change and fuel (vegetation and, in this case, structures), and how can we best mitigate this kind of fire danger?
Fire danger is a product of meteorological and fuel conditions. You also need an ignition.
Meteorology
These fires are being driven by a particularly intense Santa Ana wind event with gusts over 80 mph in many locations.
Santa Ana winds are a part of LA climate, and there is little evidence that climate change will make them worse. If anything, we expect Santa Ana winds to become less intense/frequent as the climate changes.
agupubs.onlinelibrary.wiley.com/doi/full/10.10…
Fuels are also very dry in the LA area, as there has been almost no rain so far this fall/winter. There is little evidence that climate change would be responsible for a lack of precipitation like this.
ncei.noaa.gov/access/monitor…
cal-adapt.org/tools/local-cl…
The LA area is about 3°C warmer than it would be in preindustrial conditions, which (all else being equal) works to dry fuels and makes fires more intense. Our machine-learning wildfire intensity model shows that warming is indeed contributing to increased wildfire intensity in the region with a further enhancement of 7.2% by mid-century.
met.sjsu.edu/weather/wirc-p…
eartharxiv.org/repository/vie…
The main problem with focusing on climate change (and thus emissions reductions as the solution) is that the difference between emissions scenarios is small over the next several decades. Shifting from delayed/tempered emissions reductions (RCP4.5) to aggressive emissions reductions (RCP2.6) at the global level only cuts the increase in intensity from +7.2% to +5.5%.
Fuel
The fuel situation in Southern California Chaparral brush is different than in the forests to the north (where a major problem is fire exclusion and the century-long build-up of hazardous fuels). Nevertheless, you can still do mechanical brush removal and prescribed burning fuel treatments, which reduces fire danger but comes at a cost to ecosystems.
x.com/PatrickTBrown3…
A case in point is that the recent Franklin Fire footprint seems to be protecting central Malibu from the Palisades Fire.
As shown above, our machine-learning wildfire intensity model indicates that fuel reduction in the area could more than offset the increase in wildfire danger due to warming - resulting in a 15% reduction relative to today even under delayed/tempered emissions reductions (RCP4.5).
It is notable that the US Forest Service and California Wildfire Task Force have long known the region to be high-risk, but recent and planned fuel treatments in these regions have been sparse.
x.com/PatrickTBrown3…
wildfiretaskforce.org/wp-content/upl…
app.planscape.org/map
Ignitions
These are all human-caused ignitions, and the long-term increase in the Southern California population has substantially increased them. Common causes are equipment use (sparks from chainsaws, mowers, etc.), sparks from vehicles, ATVs, dirt bikes, smoking, campfires (or fires in homeless encampments), BBQs, fireworks, and Arson. Increasing public awareness of fire safety and red flag warnings should help reduce these ignitions.
There is also the issue of utility-caused fires. Southern California Edison has preemptively shut off power in several regions to reduce the risk of powerline-caused fires. This is not an ideal solution, but it does prevent ignitions. In the longer term, we can continue to reduce vegetation around power lines, bury distribution lines, and install powerlines that automatically de-energize when they make contact with an object.
Home hardening & firefighting.
Given that extreme fire weather conditions like this will inevitably occur and given that human ignitions cannot be eliminated, protection at the structural level is also important. Houses are much more resilient to fires if they have no vegetation within 5 feet of the house, and vegetation is fire-resistant and sparse from 5 feet to 100 feet. Building codes and “home hardening” also make a difference. Things like non-combustible roofing materials (e.g., metal, tile, or asphalt shingles), ember-resistant vents with mesh screens, and fire-resistant materials for siding (like stucco, fiber cement, or metal) have been shown to be effective in the lab as well as real-world settings.
youtu.be/EY6bCS36lLI
There is also a synergistic effect, with increased overall effectiveness, as more houses in a neighborhood adopt these practices.
Also, it goes almost without saying that well-resourced firefighting (personal as well as air and ground equipment) is critical to slowing down and ultimately containing these fires.
Overall, climate change may be contributing to the fire danger of this event, but only if the warming/drying influence outweighs the potential reduction in Santa Ana winds. To me, that means climate change does not deserve primary billing (e.g., x.com/dwallacewells/…)
Fire suppression and the long-term build-up of fuels are not as much of an issue in the Southern California brush environment as they are in the Northern CA Forests, but our machine-learning wildfire intensity model indicates that fuel treatment would still reduce danger substantially.
Other than that, the main way these types of events can be mitigated in the future is via reduced human ignitions, potentially increased firefighting resources, and enhanced “home hardening” measures within fire-prone communities.
What are the primary drivers of these events and their consequences? What is the impact of climate change and fuel (vegetation and, in this case, structures), and how can we best mitigate this kind of fire danger?
Fire danger is a product of meteorological and fuel conditions. You also need an ignition.
Meteorology
These fires are being driven by a particularly intense Santa Ana wind event with gusts over 80 mph in many locations.
Santa Ana winds are a part of LA climate, and there is little evidence that climate change will make them worse. If anything, we expect Santa Ana winds to become less intense/frequent as the climate changes.
agupubs.onlinelibrary.wiley.com/doi/full/10.10…
Fuels are also very dry in the LA area, as there has been almost no rain so far this fall/winter. There is little evidence that climate change would be responsible for a lack of precipitation like this.
ncei.noaa.gov/access/monitor…
cal-adapt.org/tools/local-cl…
The LA area is about 3°C warmer than it would be in preindustrial conditions, which (all else being equal) works to dry fuels and makes fires more intense. Our machine-learning wildfire intensity model shows that warming is indeed contributing to increased wildfire intensity in the region with a further enhancement of 7.2% by mid-century.
met.sjsu.edu/weather/wirc-p…
eartharxiv.org/repository/vie…
The main problem with focusing on climate change (and thus emissions reductions as the solution) is that the difference between emissions scenarios is small over the next several decades. Shifting from delayed/tempered emissions reductions (RCP4.5) to aggressive emissions reductions (RCP2.6) at the global level only cuts the increase in intensity from +7.2% to +5.5%.
Fuel
The fuel situation in Southern California Chaparral brush is different than in the forests to the north (where a major problem is fire exclusion and the century-long build-up of hazardous fuels). Nevertheless, you can still do mechanical brush removal and prescribed burning fuel treatments, which reduces fire danger but comes at a cost to ecosystems.
x.com/PatrickTBrown3…
A case in point is that the recent Franklin Fire footprint seems to be protecting central Malibu from the Palisades Fire.
As shown above, our machine-learning wildfire intensity model indicates that fuel reduction in the area could more than offset the increase in wildfire danger due to warming - resulting in a 15% reduction relative to today even under delayed/tempered emissions reductions (RCP4.5).
It is notable that the US Forest Service and California Wildfire Task Force have long known the region to be high-risk, but recent and planned fuel treatments in these regions have been sparse.
x.com/PatrickTBrown3…
wildfiretaskforce.org/wp-content/upl…
app.planscape.org/map
Ignitions
These are all human-caused ignitions, and the long-term increase in the Southern California population has substantially increased them. Common causes are equipment use (sparks from chainsaws, mowers, etc.), sparks from vehicles, ATVs, dirt bikes, smoking, campfires (or fires in homeless encampments), BBQs, fireworks, and Arson. Increasing public awareness of fire safety and red flag warnings should help reduce these ignitions.
There is also the issue of utility-caused fires. Southern California Edison has preemptively shut off power in several regions to reduce the risk of powerline-caused fires. This is not an ideal solution, but it does prevent ignitions. In the longer term, we can continue to reduce vegetation around power lines, bury distribution lines, and install powerlines that automatically de-energize when they make contact with an object.
Home hardening & firefighting.
Given that extreme fire weather conditions like this will inevitably occur and given that human ignitions cannot be eliminated, protection at the structural level is also important. Houses are much more resilient to fires if they have no vegetation within 5 feet of the house, and vegetation is fire-resistant and sparse from 5 feet to 100 feet. Building codes and “home hardening” also make a difference. Things like non-combustible roofing materials (e.g., metal, tile, or asphalt shingles), ember-resistant vents with mesh screens, and fire-resistant materials for siding (like stucco, fiber cement, or metal) have been shown to be effective in the lab as well as real-world settings.
youtu.be/EY6bCS36lLI
There is also a synergistic effect, with increased overall effectiveness, as more houses in a neighborhood adopt these practices.
Also, it goes almost without saying that well-resourced firefighting (personal as well as air and ground equipment) is critical to slowing down and ultimately containing these fires.
Overall, climate change may be contributing to the fire danger of this event, but only if the warming/drying influence outweighs the potential reduction in Santa Ana winds. To me, that means climate change does not deserve primary billing (e.g., x.com/dwallacewells/…)
Fire suppression and the long-term build-up of fuels are not as much of an issue in the Southern California brush environment as they are in the Northern CA Forests, but our machine-learning wildfire intensity model indicates that fuel treatment would still reduce danger substantially.
Other than that, the main way these types of events can be mitigated in the future is via reduced human ignitions, potentially increased firefighting resources, and enhanced “home hardening” measures within fire-prone communities.
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