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The many ways climate change worsens California wildfires

Posted on 14 November 2018 by dana1981

This is the first entry in a Dana's new monthly column with Yale Climate Connections

NASA photoNow designated as California’s deadliest fire, the still-raging Camp Fire by November 13 had led to 42 deaths, with many residents still unaccounted for and more than 7,000 structures destroyed. (Image credit: NASA)

California has been ravaged by record wildfires in recent years. 2017 was the state’s costliest and most destructive fire season on record. The Mendocino wildfire in July 2018 was California’s largest-ever by a whopping 60 percent.

Even though California’s wildfire season has traditionally ended in October, the Camp Fire raging in November 2018 is the state’s most destructive on record.

The data tell the story: Six of California’s ten most destructive wildfires on record have now struck in just the past three years.

President Trump’s tweets suggesting forest mismanagement is to blame for California’s wildfire woes, and threatening to withhold federal funding, have prompted widespread rebukes for their insensitivity as thousands of citizens flee the fires – some, tragically, unsuccessfully – and as an affront to thousands of weary firefighters.

The reality is that about 57 percent of the state’s forests are owned and managed by the federal government, and another 40 percent by families, companies, and Native American tribes. Forest management does play some role in creating wildfire fuel, but some wildfires aren’t even located in forests. Moreover, scientific evidence clearly shows that climate change is exacerbating California’s wildfires in different ways:

  • Higher temperatures dry out vegetation and soil, creating more wildfire fuel.'
  • Climate change is shortening the California rainy season, thus extending the fire season.
  • Climate change is also strengthening the Santa Ana winds that fan particularly dangerous wildfires in Southern California.
  • The warming atmosphere is slowing the jet stream, leading to more California heat waves and high-pressure ridges in the Pacific. Those ridges deflect from the state some storms that would otherwise bring much-needed moisture to slow the spread of fires.

The Golden State’s hotter, drier conditions

Global warming causes higher temperatures, and 2014 through 2018 have been California’s five hottest years on record. This pattern leads to an increase in evapotranspiration – the combination of evaporation and transpiration transferring more moisture from land and water surfaces and plants to the atmosphere. Essentially, global warming causes plants and soil to dry out as the atmosphere holds more water vapor.

On top of this direct drying effect, climate change is causing a shift in rain patterns. Northern California has received only one inch of rain this season, which is about one-fifth of normal. A 2018 paper published in Nature Climate Change, led by UCLA’s Daniel Swain, found that as a result of global warming, California’s rainy season will become increasingly concentrated in the winter months between December and February. April, May, September, October, and November will become increasingly dry, meaning that the state’s wildfire season will start earlier and end later. As Swain noted in an informative Twitter thread about California’s November 2018 wildfires,

If Northern California had received anywhere near the typical amount of autumn precipitation this year (around 4-5 in. of rain near #CampFire point of origin), explosive fire behavior & stunning tragedy in #Paradise would almost certainly not have occurred.

With these hotter, drier conditions extending late into the year, wildfires have become larger, and they spread faster, cause more damage, and are more difficult to contain.

In Southern California, stronger Santa Ana winds

In a 2006 paper published in Geophysical Research letters, Berkeley scientists Norman Miller and Nicole Schlegel predicted that global warming would push the Southern California fire season associated with Santa Ana winds into the winter months. Those Santa Ana fires are especially costly because of the speed at which they spread due to the winds and because of their proximity to urban areas. The November 2018 Woolsey fire around Malibu and Thousand Oaks, California, is a tragic example.

Researchers of a 2015 study published in Environmental Research Letters, led by Yufang Jin at UC Davis, forecast that the area burned by Southern California wildfires will increase by about 70 percent by mid-century as a result of the drier, hotter, windier conditions caused by global warming. And these Southern California wildfires often occur outside of forests, according to the president of the Pasadena Fire Association.

Connections to the Arctic and jet stream

Rutgers climate scientist Jennifer Francis over the past decade has been researching the connection between changes in the Arctic and extreme weather patterns throughout the Northern Hemisphere. In recent years a growing number of climate scientists have found evidence supporting her groundbreaking research.

The Northern Hemisphere jet stream is a result of the temperature difference between the cold Arctic and warmer lower latitudes in regions like North America and Europe. But the Arctic is the fastest-warming region on Earth, largely because as reflective sea ice disappears, the Arctic surface is increasingly covered by dark oceans that absorb more sunlight. The rapidly-warming Arctic is shrinking the temperature difference between that region and the lower latitudes, which in turn weakens the jet stream. As a result, rather than a fast-moving flow of air, the jet stream increasingly is taking a slow, meandering path across the Northern Hemisphere.

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Comments 1 to 21:

  1. Indeed, and it's absolutely obvious climate change is making wild fires worse as below:

    Management of forests can only do rather limited things to prevent or slowdown forest fires. I mean Donald Trump is dreaming if he thinks this is the answer. La la land. You can avoid build up of scrub that is highly combustible and create fire breaks but there are no magic tools that can really prevent problems. On a windy day fire will jump over even quite large fire breaks. And management tools are expensive, and require funds the very thing Trump is hell bent on holding back from the States.

    Although it mystifies me why California allows housing to be built so close to these forests. Australia is much the same.

    Donald Trump has demanded better management of forests yet his administration has passed a little known piece of legislation called "The Resilient Federal Forests Act of 2017" which if anything increases the fire risk, and hands huge areas of forests to private interests and removes environmental assessment requirements and protections as below:

    The Jet stream is compounding the problem. However according to the modelling it will not become worse than currently provided  we keep warming to around 1.5 degrees. If warming gets above this the problem will escalate further. I think this was in the IPCC report on 1.5 degrees of warming.

    I just can't believe how unaware these politiicans and their hangers on are. We are seeing evidence of a problem with forest fires at just 1 degree, it can only get worse with more warming and drier conditions and we are on track for 3 degrees at least if nothing is done. One hopes the relationship is only linear. It looks like forest fire risk is incredibly sensitive to warming for some reason.

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  2. I happen to live in a high risk area myself, and every summer there's a period of 4-6 weeks when the combination of intense heat, high wind and low humidity conspires to create perfect fire storm potential, and much nervousness. Climate change is making fires worse in many areas but the actual incidence of ignitions is also increasing, and >90% of ignitions are human caused, either deliberately or accidentally.  Fighting climate change might prevent the situation from getting far worse in the future but it's already a serious problem in need of fast acting solutions. We can't change the climate but we can significantly reduce the root cause of the problem. 

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  3. Art Vandelay, can you substantiate your argument? You are saying that the increase in man made ignitions is a significant factor, "the root cause of the problem." However what the OP shows is that it is the change in average long term weather that is by far the most significant factor in making the fires worse. It may be the case that there are more fires happening (which would correspond to more ignitions) but you don't bring evidence to substantiate that. Nonetheless, the real problem is that the fires that do start are spreading farther, expand at mind boggling speeds and are much more difficut to control. The root cause of that problem is climate change.

    I researched the BC fires of 2017, and most information I found suggested they were started by lightning. Of course, climate change there is causing more frequent and severe thunderstorms so I guess you could say that human caused ignitions are responsible in that sense.

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  4. Santa Ana winds have made the fires worse. With global warming the increased downwelling long wave sky radiation is also making things worse. Here is how relative humidity can be increased to reduce the risk of fires: When warm dry air blows over a cold sea the air temperature near the sea surface is reduced and relative humidity (RH) near the sea surface increases and fog may occur (of course there will be more fog with hot moist air). Since net evaporation into saturated air does not occur the broader mass of air will remain dry. If you have plastic sheeting suspended quite high above the sea at an angle of 45 degrees to the sea this will force warm air downwards and will mix warm air into the air near the sea surface and evaporation will continue, humidifying a large mass of air.
    Example: If the air blowing over the sea has temperature Tair=28 deg C and a relative humidity RH=40%, then on cooling to 13 deg C at the sea surface the air will have become saturated and fog could occur above the sea surface.

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  5. The denialists have been abusing data on California wildfires to claim that the wildfires are less, not more. It even got onto the forum I usually use - The Arctic Sea Ice Forum. It has been squashed pdq.

    The article in the link below does a good job in debunking this nonsense. Perhaps another one for skepticalscience's climate myths debunked section?

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    Moderator Response:

    [PS] Activated link. Please learn how to do this yourself with the link button in the comment editor. Thank you for the link.

  6. President Trump’s tweets suggesting forest mismanagement is to blame for California’s wildfire woes

    Canada has vast areas of unmanaged forests, and climate change is increasing fires in them too.

    I'm surprised that Trump, who made (then lost, then remade) his fortune building things, seems unaware that monolithic dome homes are nearly fireproof. His self-proclaimed financial genius seems to have let him down here. There's a fortune to be made in fire-hardening the homes of people who insist on living in the increasingly firey fire country. Californians are already familiar with retrofitting buildings for earthquakes. A builder like Trump should recognize the emerging new opportunity.

    prompted widespread rebukes for their insensitivity as thousands of citizens flee the fires

    Trump's comments are insensitive because they appear to blame Californians for bringing these disasters on themselves. Trump is wrong about the mechanism, but right in a sense about the responsibility. Virtually all of the fire victims built their lives around burning fossil fuels, and will continue to burn them if they survive, thus contributing many times their global fair share to the climate change that is now coming back to bite them.

    Is it "insensitive" to tell tobacco smokers that they caused their own lung cancer? Perhaps, but it's irresponsible not to tell them. Some truths are inconvenient. Now, the difference between tobacco and climate change is that the tobacco smoker harms primarily himself or herself (although around 10% of tobacco deaths are to nonsmokers poisoned by someone else's tobacco pollution), whereas the individual's contribution to climate change spreads across the whole planet and primarily harms other people (and other species). You won't be killed by your own greenhouse gas pollution - someone else will be. (Or more correctly, you are responsible for on the order of a billionth of each of a billion future deaths, very roughly speaking, depending on your carbon footprint and on how bad climate change gets before Man's contribution fully plays out.)

    People who live in rural areas - for example in fire country - tend to have higher carbon footprints than people who live in urban areas, due to longer travel distances and the thermal inefficiency of detached homes. It's very hard to live car-free in a rural area in the United States. The choice to live there is in most cases a choice to contribute more to climate change.

    When people spend their lives pumping durable greenhouse gases into the atmosphere, who should pay the price? We've heard a lot about environmental injustice, whereby the global poor experience the bulk of suffering that results from our pampered lifestyles in the developed world. If environmental injustice is bad, then how is it not less bad when some of the people who contribute the most to climate change experience some of the costs for once? Would it be better for Africans or Bangladeshis to die in their stead?

    In the USA, we have a car-centric culture in which people feel entitled to burn all the fossils they want for their personal comfort, mobility, and prosperity, while ignoring the harm they rain down on those who can't buy their way out of the problem. Everyone posts photos from their fossil-fueled vacations on Facebook, and nobody posts apologies. When, on rare occasions, Nature flips the script and punishes the victimizers a little, our response should be one of remorse and contrition rather than solipsistic outrage as if we are somehow blameless.

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  7. Art Vandelay @2 -

    Climate change is making fires worse in many areas but the actual incidence of ignitions is also increasing, and >90% of ignitions are human caused, either deliberately or accidentally. Fighting climate change might prevent the situation from getting far worse in the future but it's already a serious problem in need of fast acting solutions. We can't change the climate but we can significantly reduce the root cause of the problem.

    The global warming potential of a unit of greenhouse gas takes centuries and millennia to play out. Therefore most of the climate change we experience now is due to greenhouse gases emitted decades ago. Since we are now emitting greenhouse gases at a much higher rate than when we were emitting the greenhouse gases that are burning California now, we are currently locking in much worse climate change for the future.

    Even worse, any action taken by any individual, organization, or nation-state to reduce greenhouse gas emissions will have no or almost no detectable effect on the local consequences of climate change the individual or organization is already experiencing. Even if California could eliminate its entire carbon footprint, humanity's global carbon footprint would only decline by about 2%, an amount below the resolution of measuring climate change impacts. Thus self-interest can play no role in fighting climate change - fighting climate change is always and only a charitable act undertaken by moral people for moral reasons. Putting up solar panels in California does almost nothing to stop wildfires in California - it is but one of billions of actions by people everywhere necessary to stop climate change.

    Climate change messaging that tries to frame the problem in terms of self-interest is logically contradictory. It's like trying to tell people they are better off if they do not steal, when in reality theft is highly profitable to the thief provided he gets away with it. Since there is no system of justice to punish carbon polluters at any level from the individual to the nation-state, committing theft by burning fossil fuels and dumping the costs on everyone else remains the perfect crime. Carbon taxes might be a start, but they'll never be implemented at a high enough level by the thieves themselves to make life as uncomfortable for the carbon polluters as it is and will be for their victims.

    But back to your stopgap strategy of reducing artificial ignitions.

    First, the problem is difficult: people like to smoke, burn things, throw glass bottles along roadsides to act as burning-lenses, consume centrally generated electricity, and be malicious. How can we protect massive areas of parched land from every jackass who wants to commit arson? Have governments figured out how to stop malicious hackers from spreading computer viruses?

    Second, you haven't justified your implied counterfactual assumption that natural sources of ignition wouldn't start more fires if human-caused ignitions weren't burning the fuel first. Perhaps if enough fuel is present, it will burn sooner or later. The longer it doesn't burn, the more fuel accumulates, thus making the eventual burn all the worse.

    The root causes of wildfires are fuel availabity and the weather conditions that allow fuel to burn. Proximal causes include every source of ignition. But given enough fuel and enough time with the wealther conditions for fire, even a low rate of natural ignitions should eventually burn everything that can burn. Is there evidence from the fossil record that during past natural periods of warming and/or drying when fire risks were increasing, the potential for fire went unrealized because there weren't humans around to light matches or build defective power lines?

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  8. Philippe Chantreau says "It may be the case that there are more fires happening (which would correspond to more ignitions) but you don't bring evidence to substantiate that."

    The data is readily available from relevant government agencies. For the mainland US States it's around 90% that have a human ignition.  Obviously, more humans can only result in more human ignitions, and it's difficult to stop urban creep into more fire sensitive hinterlands. 

    As was pointed out in the post above , we can't stop CC any time soon but there is very considerable scope to reduce ignitions as well as scope to improve forest management, and that's where the focus needs to be right now, because what else is there?  

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  9. Art Vandelay, "relevant government agencies" is rather vague. I don't see that you have actually done the work to back up your assertions. NOAA has wildfire statistics for the period 2000-2017 on the following page:

    I have not done a statistical analysis of the numbers, however at first glance, there is no easily discernable trend in the number of fires starting. The acres burned does seem to show an upward trend. The highest number of fires is reported in the first year of the period, over 7600 fires. Considering that the population did increase over the period, it seems that these data do not support your hypothesis of more people simply igniting more fires. I looked at NOAA, FEMA and USGS and could not find categorizations of fires by ignition source. Where does that 90% figure come from?

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  10. Where does that 90% figure come from?

    "As many as 90 percent of wildland fires in the United States are caused by humans. Human-caused fires result from campfires left unattended, the burning of debris, negligently discarded cigarettes, and intentional acts of arson.Nov 17, 2017"

    Information found in 0.02S

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    Moderator Response:

    [JH] Snark snipped.

  11. It would be nice if the Park Service would refer to sources for this kind of statement. Nonetheless I'll take it. It mathches what is on Wikipedia. In Canada and other regions, natural causes are more frequent sources of ignition. The recent situation in Canada points to climate change as a major factor in the severity and duration of the fire season, as is explained by Natural Resources Canada.

    The fact that the number of fires per year is as variable as NOAA shows is interesting in that light. The highest year in their 18 year record has 4 times as many fires as the lowest and the number of fires does not follow the expected distribution of an increasing population. That would suggest some pretty wild variations in human behavior from one year to another, which warrants some skepticism.

    In any case, if we are to consider the recent California fires, the root cause of their catastrophic nature and unprecedented speed of expansion have nothing to do with their ignition sources. 

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  12. My understanding is typically about 80% of wild fires are caused by human factors, (campfires, discarded cigarettes, and arson) and lightening causes about 20%. But more forest area is destroyed by lightening because its in more remote hard to access areas.

    Number of human caused ignitions does appear to have increased a little  for some specific types of fires.

    Climate change is also causing more ignitions because dry areas are more susceptible to all ignition sources whether a discarded cigarette or a lightening strike.

    Climate change is causing larger areas to be burned and increasing fire intensity.

    Climate change is also causing more lightening strikes.

    I think it would be very difficult to reduce problems like campfires and arson, because it's so hard to identify the perpetrators, and probably not politically practical to ban campfires. If we want to reduce the forest fire problem our best bet might actually be reducing emissions.

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  13. nigelj@12:  "If we want to reduce the forest fire problem our best bet might actually be reducing emissions".

    Unfortunately, reducing emissions won't help in the short or medium terms, and a case in point is the USA, where emissions have fallen against a rising incidence and severity of forest fires. That's not a reason not to reduce emissions of course, but rather an acknowledgement of reality.

    The solution(s) to reduce severity and incidence will differ for different areas of the globe, but will obviously involve better monitoring and management methods. In some cases it may even involve partial clearing. If 90% have a human cause it does at least provide reasonable scope to reduce ignitions. For instance, in my part of the world, scientists estimate a 10% increase in risk due to climate change, but ignitions have actually reduced over the past 20 years thanks to government education programs to make people more aware and diligent, and better forest management, which includes hazard reductions during winter.

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  14. Art Vandelay @13 ,

    a small nitpick : California's wildfire risks are influenced by the ongoing rising global CO2 emissions ~ regardless of whether (or not) the USA's emissions have fallen in recent years.

    (Of course, reducing local wildfire incidence & severity, is a difficult and expensive task.)

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  15. Art Vandelay @13

    Partial clearing is not going to solve the problem, according to this scientific expert. 

    You say in comment @2 "the actual incidence of ignitions is also increasing," and now you say "but ignitions have actually reduced over the past 20 years thanks to government education programs"

    Which is it? You are not very consistent or convincing.

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  16. Many of southern California's brush fires get started during the Santa Ana windstorms.  The ones that grow past a few acres are almost impossible to stop until the winds die down.  A big factor in the severity of these fires is the frequency, duration, and intensity of these windstorms.  As a long time resident of California, it seems like we may be seeing an increase in all three parameters.  But, I have to wonder if there is any data.  It seems difficult to quantify.

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  17. Southern California has had Santa Ana winds for a long time.  However, the conditions seem to be getting more common in northern California over the past few years.  We definitely had that weather pattern as the recent Camp fire was getting started.  If I recall correctly, last years wine country fires got started under similar conditions.  We did not get these every year in the past in northern California.

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  18. nigelj @ 15: "You say in comment @2 "the actual incidence of ignitions is also increasing," and now you say "but ignitions have actually reduced over the past 20 years thanks to government education programs"

    "Which is it? You are not very consistent or convincing".

    If you read my posts again you'll find that there's no "inconsistency" at all. 

    And I would be surprised if there aren't other regions or localities that are also bucking the global trend for similar reasons.   

    Eclectic @ 14 says, "a small nitpick : California's wildfire risks are influenced by the ongoing rising global CO2 emissions ~ regardless of whether (or not) the USA's emissions have fallen in recent years.

    (Of course, reducing local wildfire incidence & severity, is a difficult and expensive task.)"

    OK, I confess, your small nitpick was anticipated, and i agree with you of course, on both points.

    Reducing the incidence and severity of forest fires will definitely be challenging in many cases, and probably also expensive. The question is, do we accept that challenge or do we simply ignore it and focus solely on reducing CO2 emisions?

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  19. Recommended supplemental reading:

    California’s wildfires are hardly “natural” — humans made them worse at every step by Umair Irfan, Energy & Environment, Vox, Nov 19, 2018

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  20. Art Vandelay @18, fair enough you are not being incoinsistent, some places are having success reducing ignitions. I was being a bit overly suspicious of your comments.

    "The question is, do we accept that challenge or do we simply ignore it and focus solely on reducing CO2 emisions?"

    Obviously we do both, but management of forest fires is off topic. We are supposed to be talking about climate change.

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  21. nijelj @ 20, "Obviously we do both, but management of forest fires is off topic. We are supposed to be talking about climate change."

    I see and hear quite a bit of media commentary - to the effect that "forest fires" is why we should act on climate change.

    As if there aren't enough reasons already. 

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