How Climate Worsens Fires

November 16, 2018

Dana Nuccitelli has joined the stable of great science communicators at Yale Climate Connections.

Dana Nuccitelli at Yale Climate Connections:

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 shifting 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.

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.

These are the many ways in which climate change is clearly connected to California #wildfires. 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 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.

Jet stream pattern
A wandering jet stream pattern. (Photo credit: NASA)

In between these jet stream waves, weather patterns have a tendency to stall in place. These patterns include heat waves, the polar vortex, hurricanes and associated record rainfall, and high-pressure ridges, and the latter has tended to occur off the California coast. During the drought of 2012 to 2016 – California’s worst in over a millennium – a high-pressure ridge in the Pacific was so persistent, that Swain coined it the “Ridiculously Resilient Ridge.” A similar system has formed off the coast in late 2018:

High pressure ridge

11 Responses to “How Climate Worsens Fires”

  1. I’ve already seen wingnuts try to blame the Paradise disaster on “invarnmentalists and the gummit” for interfering with forest clearing/thinning projects.

    But that is complete nonsense. Much if not most of the land between the #CampFire ignition point and the town of Paradise was burned off just 10 years ago in the Humboldt Fire. The majority is also privately-owned (can’t pin privately-owned acreage that burned on USFS policies).

    So basically, many thousands of acres of land outside Paradise were cleared and thinned by fire a decade ago.

    This can be verified by zooming into the area via Google Maps satellite view.

    Here is a good place to start:,+CA+95969/@39.7710337,-121.5386609,17526m/data=!3m1!1e3!4m5!3m4!1s0x80832bd49578303f:0x50c92f9d6b33aa70!8m2!3d39.7596061!4d-121.6219177

    The ignition point is in the northeast corner. The town of Paradise is in the southwest. Zoom in on the land in between and you will find brush, burned up trees, and what appear to be manicured tree farms (with trees less than 10 years old). The areas that appear to be replanted with trees are most likely owned by timber companies.

    So that land was thinned and cleared as aggressively as you could imagine, but the fire still burned through it all in just a few hours. The fire reached Paradise so quickly that many people didn’t have a chance to evacuate safely.

    And, mind you, this happened in *November*. A 140,000 acre wildfire in the Northern California Sierra in *November* is an off-the-charts black-swan event. By this time of year, that area should have received several inches of precipitation to start off the rainy season.

    Forest management had nothing to do with this disaster. The fire burned right through a whole bunch of already-burned-over privately-managed forest.

    And as far as wildfires here in California are concerned, we have been hit with a whole flock of black swan events.

  2. Oops — sorry about that long link. Should have buried it in a tag.

    Blame it on lack of coffee. (Got to point the finger somewhere.)

  3. Zen-fro Sven-dog Says:

    I feel for these folks, PG&E probably effed up, and climate change made it much worse. But it’s amazing that the entire town seems to have been built in what the late western writer, publisher, and pundit Ed Quillen called The Stupid Zone: someplace that WILL burn, sooner or later, and you’re stupid if you build there and/or if you don’t at least plan on fire coming for you. Furthermore, this Stupid Zone town is built stupidly: houses within forest, built out of non-fire-resistant materials, no defensible spaces surrounding them.

    It’s hardly the only place built like that. I suppose they will rebuild just like they did before…and eventually it will burn again.

    • Some additional depressing thoughts…

      What’s really horrifying is the fact that realtors and other “local yokels” have for years been encouraging retirees to move to Paradise and other settlements in that godawful western Sierra tinderbox. But when you are collecting a nice commission for every mountain hideaway you sell, who cares?

      I’ve been all over the Sierra; the west side has turned into a giant fire-trap. It’s the *last* place where you want old folks who aren’t very mobile to be moving to. Or *anyone*, for that matter. Thanks in large part to climate-change, much of the western Sierra has been transformed into the equivalent of a highly-flammable high-rise building with no fire escapes.

      And it’s going to get worse. Far worse. Thousands of people who thought that they’d found their little paradise in the western Sierra forests will soon realize that they are trapped in homes they can’t insure, can’t sell and can’t afford to walk away from.

      Every summer and fall, they will be sleeping with one eye open. When the diablo winds kick up, they won’t be sleeping at all.

      For the Camp Fire, the latest number of the “unaccounted for” has exceeded 1,000 (and is likely to go higher). Even if the vast majority are found safe and sound, the ultimate death toll will be horrific.

      • dumboldguy Says:

        Yep, the greedy bastards have been encouraging people to move to “dangerous” places for as long as the idea of “get rich on OPM” has been around. Not just the western Sierra, but in South Florida, flood plains along rivers, and sea coasts everywhere—-remember NC 20?—the coalition of NC landowners, developers, builders, and Chambers of Commerce that insist NC will only have 20 cm of sea level rise by 2100 because they still have “oceanfront” property to sell and houses to build?

        As Sven-dog says, people who suffer from denial of scientific reality (and are protected by private and government “insurance”) will continue to build and live in the “Stupid Zone”, at least until they get burned-flooded-mudslided enough times that the whole charade collapses.

  4. Sir Charles Says:

    Very good article by Dana. But unfortunately too long and too difficult for that moron in chief.

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: