A long view of California’s climate

Public Release: 4-Mar-2019

Study examines centuries of data to understand climate-wildfire links

NOAA Headquarters

The North Pacific Jet (NPJ) travels eastward at variable wind speeds and directions toward California at an altitude of about 11 kilometers above the ocean’s surface. The strength and position of the winds take on importance in relation to the amount and intensity of moisture the jet stream delivers. This graphic represents a winter-average path of entry to California that could produce a very-wet, low-fire season in the state. Credit NOAA NCEI

Deadly severe wildfires in California have scientists scrutinizing the underlying factors that could influence future extreme events. Using climate simulations and paleoclimate data dating back to the 16th century, a recent study looks closely at long-term upper-level wind and related moisture patterns to find clues.

The new research published by the Proceedings of the National Academy of Sciences USA examines jet stream and moisture patterns in California over a centuries-long time period–1571 to 2013–which is nearly four times longer than the instrumental period of record that begins in the latter part of the 19th century. The length of the study enhances the understanding of dynamics that may contribute to extreme impacts from wildfires, as well as precipitation extremes. The work provides a stronger foundation and a longer-term perspective for evaluating regional natural hazards within California and the economic risks to one of the world’s largest economies.

Between 2012 and 2018, several deadly and costly extreme wildfire events impacted California, including some of the state’s largest and most destructive wildfires on record. In 2018, California experienced several of its costliest, deadliest, and largest wildfires to date, according to records that date back to 1933. Such extreme events, which are tracked by NOAA National Centers for Environmental Information (NCEI) in its Billion-Dollar Weather and Climate Disasters reports, prompt concern for the future.

Each scientist on the research team brought different perspectives and necessary knowledge to the study. These included expertise in paleoclimatology and paleoecology as well as wildfire research. The international, multi-disciplinary approach needed to execute the research underscored the many factors that can contribute to extreme weather and climate events.

The Jet Stream and Moisture

Moisture in California is largely regulated by the strength and position of the North Pacific Jet (NPJ) stream, high-altitude winds that sweep into the state from the west during the cooler wet season. The study evaluated the NPJ between December and February. The strength and position of the winds influence regional conditions that carry over into the warmer dry season, when wildfires are more prone to occur. The wet-season NPJ thus becomes an important precursor of summer fire conditions.

To build a better understanding of the influence of the NPJ over time, scientists focused on winter NPJ variability in a period of more than 400 years. Using paleoclimatological and historical data, such as tree rings and historical fire records, past conditions were reconstructed to show connections between the NPJ and moisture and forest fire extremes.

The team wanted to gain a greater sense of conditions before and after fire suppression methods became more standard in 1904. The researchers constructed a list of low- and high-fire years in the Sierra Nevada for 1600-1903 from the paleo records. Extreme instances from both pre- and post-suppression period were then evaluated.

Very recently, 2017 bucked a pattern seen in the longer record. The severe Tubbs and Thomas fires of 2017, a high-precipitation year, overrode the NPJ’s historical relationship with low-fire extremes after cool seasons of very high moisture. Extreme precipitation had compromised the Oroville Spillway earlier that year in addition to bringing about dangerous floods and landslides. Prior to modern fire suppression, the paleoclimatic reconstruction showed no cases of a high-precipitation year coupled with a high-fire year. If warming continues, as is the scientific consensus, then significant wet season rain and snow may not ensure a quiet fire season afterward.

“Recent California fires during wet NPJ extremes may be early evidence of this change,” the paper states.

Besides fire risk and its associated health and economic impacts, such a change could alter species distribution, forest composition, and ecosystems.


Along with NOAA NCEI, contributors to the study came from the Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research in Germany and the Integrated Climate System Analysis and Prediction (CLiSAP) Cluster of Excellence at the University of Hamburg, The University of Arizona’s Laboratory of Tree-Ring Research, and Penn State University’s Department of Geography and Earth and Environmental Systems Institute.


Eugene Wahl, NOAA National Centers for Environmental Information
Eduardo Zorita, Helmholtz-Zentrum Geesthacht
Valerie Trouet, University of Arizona
Alan Taylor, Penn State University

From EurekAlert!

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March 4, 2019 6:10 pm

“Deadly severe wildfires in California have scientists scrutinizing the underlying factors that could influence future extreme events. Using climate simulations and paleoclimate data dating back to the 16th century”

If the only tool you have is a hammer everything looks like nails.



Curious George
Reply to  Chaamjamal
March 4, 2019 6:23 pm

What is the difference between a climate simulation and a climate speculation?

Reply to  Curious George
March 4, 2019 6:57 pm

I’ll take “absolutely nothing” for $800, Alex.

Tom Halla
March 4, 2019 6:17 pm

Current wildlands management practices have only been in place since the 1990’s, so thirty or so years is not long enough to attribute any relationship between rainfall totals and fire risk. California normally gets dry enough every summer to have fires, so a wet winter the season before would just mean more fuel.

Paul Johnson
Reply to  Tom Halla
March 4, 2019 9:52 pm

And poor forest management adds even more to the fuel load. Trees leave the forest in only two ways, as timber or as smoke.

Peter Daubeny
Reply to  Paul Johnson
March 4, 2019 11:06 pm

Or as CO2, as they rot.

Loren Wilson
March 4, 2019 6:25 pm

Maybe they should look at what has changed in regards to fire management, rather than just focusing on the weather. There are more variables in the equation.

A C Osborn
Reply to  Loren Wilson
March 5, 2019 1:44 am

But you can’t blame Fire Management on CO2, so that is definitely out.
It must be climate related or you ignore it to be a “proper” Scientist.

ps CO2 is great fire extinguisher

Gene Selkov
Reply to  A C Osborn
March 5, 2019 7:40 am

When stored in a liquid form, in a bottle.

I had an incident at work that made a lot of people laugh. Not long ago, my then-boss got a kick out of telling that story to my prospective employer, when asked for a reference.

I locked myself out of a car in front of my office building with its engine running. The car was not mine and I didn’t know it would automatically lock its doors with key in ignition. I really didn’t like the idea of letting the car run out of gas in the middle of a winter night while I as looking for a way to fetch a spare key. So I thought I’d just run upstairs, borrow some CO2 and smother the engine through the intake. That didn’t quite work out as I expected. It took almost half-an-hour of trial and error, blowing inside the engine through the front grille, at full blast, until the steam of CO2 finally hit the intake at just the right angle. The engine finally quit, reluctantly, seconds before the 50lb cylinder of CO2 was empty. Or frozen — not sure what it was. The first attempts to simply jet the gas straight out of the open valve were unsuccessful. It worked only when I attached a piece of tubing to it and pushed it through the grille toward the general area of the intake, and then it took a lot of probing and poking around before the engine began to stutter.

Dave Fair
March 4, 2019 7:46 pm

In only one year, 2017, out of all the centuries of data, did they see that unique wet/fire pattern. The ‘study’ authors take that one year and speculate about it being the norm in the future.

Did anyone review the ‘study’ before its publication? Did nobody ask the authors about the scientific oddity of relying on one data point to extrapolate the future? CliSci is cargo cult science.

Oh, BTW, UN IPCC climate models are bunk.

Neil Jordan
Reply to  Dave Fair
March 4, 2019 8:01 pm

The beauty of using only one data point is that an infinite number of lines (or hockey sticks) can be extrapolated through it. The data point becomes the horizontal axis of a wheel or fortune or the vertical axis of a roulette wheel. WUWT covered this concept some time ago with a MIT modeling post:

Joel O'Bryan
Reply to  Dave Fair
March 4, 2019 10:58 pm

Hey, they did use the qualifier “may be” to that statement:

“Recent California fires during wet NPJ extremes may be early evidence of this change,” the paper states.

One can conclude anything with “may be.”

I would offer to Gene Wahl the following as equally valid statement of their work:

“The recent 2017 wet NPJ extreme coupled with the California fires that year may be a warning that our research is just junkscience.

Dave Fair
Reply to  Joel O'Bryan
March 4, 2019 11:11 pm

What little I read seemed confused. Are they saying the wet NPJ will become more common? If so, what physical mechanism, caused by CO2, is driving it? Clarity is not the ‘study’ authors’ strong suite.

Reply to  Dave Fair
March 5, 2019 12:37 pm

Clarity is the harbinger of Reality…

Pop Piasa
Reply to  Yirgach
March 5, 2019 7:24 pm

…and the enemy of the Green Axis of Indoctrination.

Gerard J O’Dowd,M.D.
Reply to  Dave Fair
March 6, 2019 11:31 am

Why didn’t the one data point of Wet year followed by Fire year elicit the idea that the unique sequence of events may not have due to natural causes but due primarily to the consequences of human decisions(other than GHG) such as neglect of utility maintenance/repair obligations or actions with criminal intent i.e. arson? The WSJ had a review of the repeated delays over 5 yrs of PGE fixing known problems of the century old high voltage power line called “Caribou-Palermo” in the Thursday 2/28/19 edition. The repairs were never made. The proximate cause of the deadly Camp wildfire on Nov 8,2018 may have been due to high winds causing a wire to snap, break free, and result in an electric arc that scorched the metal tower supporting it. A quarter acre fire was reported by a PGE worker around sunrise. The tragedy may have been averted had PGE executed its repair plans on the CP line as reported was its intent to Federal regulators in 2013 to replace many towers, wires, and hardware on the line. The entire line has now been shut down after additional problems were discovered by linemen in Dec. How can any of that history of neglect be related to GHG emissions?

March 4, 2019 8:03 pm

When I drive from the Nevada side, where a great deal of effort is put into thinning measures and controlled burns, to the California side, the difference is noticeable. The forest and underbrush are so thick on their side, you couldn’t walk through.

Just manage your forests better, Cali.

Reply to  Adsm
March 4, 2019 9:25 pm

I live in Reno. The Nevada side of the Sierra is very much in the “rain shadow” and drier than the California side, so the forest and understory are naturally much thinner. That’s not to assert that Nevada forest management is no better than California’s, just that their task is simpler.

Reply to  brians356
March 6, 2019 6:55 am

The eastern slopes of the Sierras were stripped of trees during the Nevada silver mining era.

Richard Patton
Reply to  Adsm
March 4, 2019 9:40 pm

I see the same thing as I cross the Cascades in Oregon. It takes just a few miles for the heavily forested Douglas Fir to give way to open understory Ponderosa. Gee, do you think it is difference in forest management? NOT. It’s called rain shadow. That’s why Nevada is mostly desert.

SLC Dave
March 4, 2019 8:15 pm

We need to get better at managing the fuels. The problem is that people love to claim that logging will solve the problem but that only part of the issue. Many of the west’s most damaging fires are fueled more by dry brush and grass than trees. Logging companies also leave behind tons of slash which dries out quickly and becomes a fire hazard in itself. Controlled burns are currently our best method of controlling these fires but they are risky and cause a tremendous amount of pollution, which can make them unpopular with local communities. I think another option would be to harvest the slash and underbrush and burn it in bio fuel power plants. Of course, this kind of system would probably barely break even if at all, meaning that it would have to be funded by the government, and we all know how that goes…

March 4, 2019 8:53 pm

Concur with Loren Wilson. The problem is that nothing can erase human impacts from the climate-wildfire risks. Increasing population, wildland-urban interface, poor or improper forest management (or mismanagement) and many others. Fires are bigger and badder because they explode into unnaturally overgrown fire suppressed areas. The cost of wildland fires increases because more expensive stuff burns, e.g. Nov 2018 Woolsey Fire in Malibu. If humans never settled in California, I think the study would have shown very good uniformity.

March 4, 2019 9:15 pm

Nonesense. One of the wettest California winters, featuring several strong atmospheric rivers and one of the best Sierra Nevada snowpacks on record, was 2016/2017. Yet, the subsequent summer of 2017 was the most destructive wildfire season on record in California at the time, with a total of 9,133 fires burning 1,381,405 acres of land. A very wet winter only serves to produce abundant fuel for summer wildfires. It’s the dry hot weather that occurs after the wet season that most influences the severity of a fire season.

Tom Abbott
Reply to  brians356
March 5, 2019 3:50 am

“It’s the dry hot weather that occurs after the wet season that most influences the severity of a fire season.”

Yes, and it doesn’t take long for a strong wind to dry out the vegetation even if there has been a lot of rain..

March 4, 2019 9:33 pm

No mention of ENSO, so they didn’t put many tools in their bag. Further, we Californians recognize that a wet period produces growth which dries all summer and is ignitable in October and November before the next rainy season starts. The adiabatic winds produced by land cooling faster than the ocean become very strong as they race down mountains and hills on their way to the sea. Low lying fuel such as brush and houses feed flames driving through areas at ground level, only singeing the tall trees the fire passes under. An article in the Los Angeles Times described what was going to happen in Paradise twenty years before the fire hit. The same area of Santa Rosa was burned in 1963 but didn’t have the houses in the area then to feed the flames. In Southern California they have the Santa Anna winds; same effect. Now we have areas along the Russian River, Guerneville in particular, that flood periodically. Again, ENSO explains this cycle too. The only difference now compared to previous periods in California is that the things happening now have a lot more human-built structures to flood and burn than earlier. We knew that a long time ago and this study adds nothing new.

Reply to  Michael Combs
March 5, 2019 12:33 am

In the Pacific Northwest they are Chinook winds. There’s also “Chinook Jargon”, some terms of which were still in use by my father’s generation, for example “skookum”.

Stan Sexton
March 4, 2019 9:41 pm

The intensity of the fires is environmental and due to poor forest management. But the frequency of the fires must include the acts of man. No one talks of the subject of a big U.S. Forest Service Conference of a few years ago. If you Google “Pyroterrorism” you will read about fires initiated by remote-controlled incendiary devices by believers in Jihad against the United States. Most of these device-induced fires leave no evidence, but the Forest Service has found enough remnants to conclude that pyroterrorism is a factor in many fires. There are web sites in Arabic that promote and illustrate the building of these devices. Again, Google “Pyroterrorism”.

Reply to  Stan Sexton
March 5, 2019 2:44 pm

It’s not the weather, nor climate starting these fire in the west. My ranch had a fire two years ago. Started along the road. Across the river last summer another big FEMA fire….started along the highway. Speaking of FEMA….follow that money train. Infact, other than lightning strikes, the fires are started by humans…along roads. When approaching a DNR person, who winks, and says: “the fires will be worse next year (2019)…lots of money to be made…”

So don’t be naive here. People are starting many of these fires. It’s the latest thing to do and easy to get away with.

Also, I agree that wet winters produce more under brush that in the dry months becom fuel. I’ve witnessed many dry winters whereas the under brush dwindles away and receeds. However, the last few winters have had substantial moisture and the under brush is very happy to return.

Ulric Lyons
March 5, 2019 3:59 am

“The severe Tubbs and Thomas fires of 2017, a high-precipitation year, overrode the NPJ’s historical relationship with low-fire extremes after cool seasons of very high moisture.”

Rubbish, there were massive wildfires in the southwest in 1879 following the 1877-78 Super El Nino rains.

“If warming continues, as is the scientific consensus, then significant wet season rain and snow may not ensure a quiet fire season afterward.”

In fact as this solar minimum continues there will continue to be increased El Nino conditions and regular strong regrowth to fuel to more fires.

Hocus Locus
March 5, 2019 5:00 am

The graphic reminds me of my Dad’s advice, keep yourself healthy and in shape so you can outrun the proctologists.

March 5, 2019 5:11 am

Within 36 hours, the Arctic air will attack both on the east and on the west coast of North America.
comment image

Dave Fair
Reply to  ren
March 5, 2019 1:15 pm

“Within 36 hours, the Arctic air will attack both on the east and on the west coast of North America.”

Whar’s muh musket, maw? Them Eskeemos is commin!

Reply to  Dave Fair
March 6, 2019 9:10 am

Central Arctic totally froze in March.
comment image

Johann Wundersamer
March 5, 2019 5:16 am

“If warming continues, as is the scientific consensus, then significant wet season rain and snow may not ensure a quiet fire season afterward.

“Recent California fires during wet NPJ extremes may be early evidence of this change,” the paper states.”


Finally they found a way to produce their lies without “supercomputers” and sophisticated? “Climate models”.

Even to build their alarmism approach on understandable language.


March 5, 2019 5:20 am

The expected rainfall in California will be calm. It is not an atmospheric river.
comment image

Reply to  ren
March 5, 2019 7:28 am

Models are showing Winter conditions will begin to rapidly ameliorate over about 3/4 of N America during the next week to 10 days.


Ernest Bush
Reply to  WXcycles
March 5, 2019 8:36 am

Joe Bastardi predicts that in about a week after warming up across the country most areas will then return to winter and snow. I’d suggest you take that into account for any travel plans for the last part of March. Currently the Weatherbug and Weather Underground apps show Yuma, Az, with highs dropping to the high 60’s starting Friday. This is highly unusual. We are currently having highs in the low 80’s.

Dave Fair
Reply to  WXcycles
March 5, 2019 1:22 pm

“ameliorate,” really?

Dave Fair
Reply to  ren
March 5, 2019 1:21 pm

That’s cause them Eskeemos em are attakin from the Nor East and drivin back dem dirty NPJaps! [Lord, forgive me.]

Tom Johnson
March 5, 2019 6:12 am

If warming continues, as is the scientific consensus……..

Read no farther. Facts are not relevant to the propaganda that ensues.

Steve Oregon
March 5, 2019 7:34 am

This modeled forecast seems to have predicted the opposite of what is occurring.

With this year SWE rising to another epic year like 16-17 the decade is starting to resemble the 50s or 60s.

A G Foster
March 5, 2019 9:22 am

Clearly invasive species are the more significant factor (in addition to fire suppression and logging bans, of course): eucalyptus has taken over and is highly flammable. What was once desert is now flammable forest: https://www.californist.com/articles/2016/3/17/whats

Tom Halla
Reply to  A G Foster
March 5, 2019 10:10 am

I used to live in the part of California where eucalyptus has thrived. Most of the area was formerly the southern margin for Coast Redwood, or somewhat dryer areas that were oak and such. It was normal Mediterranian flora, not a “desert”.

A G Foster
Reply to  Tom Halla
March 5, 2019 12:25 pm

And that’s obviously a more serious concern than desert greening, but more typical of the north than of southern CA, at least according to the link: “And at the time [1895], California, especially southern California, was a largely treeless landscape, so having eucalyptus grow so well easily changed the look of the state almost instantly.” And this was after considerable deforestation. When I lived in CA in the 60’s they were still making fences out of redwood. –AGF

Reply to  A G Foster
March 6, 2019 6:49 am

I used to make a few bucks making roofing shingles out of redwood blocks back in the early 1970s. The price of redwood lumber at the time was around 300 dollars per thousand board foot. Now redwood costs 10 times that much.

March 6, 2019 6:41 am

Speaking of snow in the Sierras the coastal mountains on the west side of the Sacramento Valley have been experiencing an absolute downpour for most of the last hour, after steady rains all night long. It is after 6 in the morning now. This will hit the Sierras later on today; and if it does similar, then the snow is going to dump in the mountains.

March 6, 2019 6:56 am

Must-see ‘super bloom’ of California wildflowers taking over desert landscapes.
“The rain has hit us nearly perfectly,” McElhatton said. “We are going to have a really widespread bloom; in the past, we have seen only small concentrations in select valleys. This year, it already appears that a vast majority of the 50-mile park will be in bloom.”

It isn’t just those working within the park that have noticed the bloom upon us. Towns bordering the park have already began to experience visitors, with campgrounds quickly filling up. Everyone seemingly interested in getting a glimpse at the bright display the flowers put on.

In the coming weeks, the views are only expected to get better as the California poppy comes fully into bloom in the beginning of March, covering the ground in orange.

March 6, 2019 7:08 am

Absolute downpour here in the coastal mountains on the edge of the Sacramento valley for the last 2 hours. The Sierras are going to get a huge snowfall.

CC Reader
March 6, 2019 10:03 am

What caused the devastating fires in California?

“As timber harvesting permit fees went up and environmental challenges multiplied, the people who earned a living felling and planting trees looked for other lines of work. The combustible fuel load in the forest predictably soared. No longer were forest management professionals clearing brush and thinning trees.”

March 6, 2019 3:17 pm

Huge rains down in LA from an AR which struck the area for the last 2 days. …https://www.latimes.com/local/lanow/la-me-ln-lightning-rain-20190306-story.html

What an amazing winter. Heavy downpours still popping up every hour or two here in Northern Calfiornia.

Reply to  goldminor
March 7, 2019 12:50 am

Cold air will remain over California.
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March 13, 2019 8:47 pm

California wildfires are very easy to understand. The State has a Mediterranean climate, which means wet cool winters and warm dry summers. The state is in drought every single year, from about April through September, when no rain falls. What varies is the amount of rainfall in winter. When there is a lot of rain, there is a lot of plant growth. Much of this plant growth dies during the dry summer. Hence the wetter the winter, the worse the summer wildfires. We just had a wet winter. Native California grasses are perennials. The state has been taken over however by non-native annual grasses that die in the waterless summer. Lightning sets natural fires. A fairly low percentage of California’s fires are set by lightning. Most are set by human causes. A carelessly tossed cigarette, an automobile engine fire, a spark from a trailer chain, fault electrical equipment. The population continues to grow hence the damage continues to grow. But the fire cycle is not caused by a dry winter. Fuel doesn’t grow and build up during a dry winter. The fire cycle here is due to wet winters, dry summers, non-native annual grasses, and human-set fires. TempJerature doesn’t really enter into the equation.

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