Claim: California’s Rainy Season Starting Nearly A Month Later Than It Did 60 Years Ago

From The AGU [See update at the end—w.]

4 February 2021

A dry California riverbed in 2009. New research finds the start of California’s annual rainy season has been pushed back from November to December, prolonging the state’s increasingly destructive wildfire season by nearly a month.  Credit: NOAA.

WASHINGTON—The start of California’s annual rainy season has been pushed back from November to December, prolonging the state’s increasingly destructive wildfire season by nearly a month, according to new research. The study cannot confirm the shift is connected to climate change, but the results are consistent with climate models that predict drier autumns for California in a warming climate, according to the authors.

Wildfires can occur at any time in California, but fires typically burn from May through October, when the state is in its dry season. The start of the rainy season, historically in November, ends wildfire season as plants become too moist to burn.

California’s rainy season has been starting progressively later in recent decades and climate scientists have projected it will get shorter as the climate warms. In the new study, researchers analyzed rainfall and weather data in California over the past six decades. The results show the official onset of California’s rainy season is 27 days later than it was in the 1960s and the rain that does fall is being concentrated during the months of January and February.

“What we’ve shown is that it will not happen in the future, it’s happening already,” said Jelena Luković, a climate scientist at the University of Belgrade in Serbia and lead author of the new study. “The onset of the rainy season has been progressively delayed since the 1960s, and as a result the precipitation season has become shorter and sharper in California.”

The new study in AGU’s journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences, is the first to quantify just how much later the rainy season now begins.

The results suggest California’s wildfire season, which has been getting progressively worse due to human-caused climate change, will last even longer in the years to come and Californians can expect to see more fires flaring up in the month of November. 2020 was California’s worst wildfire season on record, with nearly 10,000 fires burning more than 4.2 million acres of land.

An extended dry season means there is more overlap between wildfire season and the influx of Santa Ana winds that bring hot, dry weather to California in the fall. These winds can fan the flames of wildfires and increase the risk of late-season fires getting out of hand.

Full press release can be read here.

Paper here.

[UPDATE: I suspect Charles won’t mind if I add a bit of historical perspective to these claims. Here is the Cook et. al. analysis of the drought situation in the western US since the year 800 … posted without further comment.

w.]

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D Boss
February 5, 2021 6:11 am

Tony Heller produced a chart showing California drought over the past showing it is naturally cyclical and has been worse than now:

https://realclimatescience.com/2018/02/science-man-made-california-droughts/

“Scientists who study the West’s long-term climate patterns say that California has had multiple droughts of 10 or 20 years in a row during the past 1,000 years — and two severe “megadroughts” of 180 years and 240 years.”

Vuk
Reply to  D Boss
February 5, 2021 7:15 am

“Tony Heller produced a chart showing California drought over the past showing it is naturally cyclical ”
Absolutely.
California rain follows Pacific Ocean currents, faster currents more water moved northwards, and thanks to the size of the Pacific the Earth’s angular momentum changes, slightly altering length of the day LOD.
http://www.vukcevic.co.uk/CaRainSC.gif
Spectral composition of the California’s ran follows closely the LOD’s spectral composition with a strong ~ 30 year periodicity and it’s second 14-15 year harmonic
 

Last edited 2 months ago by Vuk
Vuk
Reply to  Vuk
February 5, 2021 7:18 am

Spectral composition

CaRainSC.gif
lee riffee
Reply to  D Boss
February 5, 2021 7:33 am

I was just thinking while reading the article that “how do they know that California wasn’t abnormally wet back in the 1960’s?” And according to Tony Heller’s graph, it appears that was the case.

jorgekafkazar
Reply to  D Boss
February 5, 2021 12:38 pm

Not a surprise. An onset date is an extremely chaotic variable related to the even more chaotic variable of rainfall, so I suspect we’re looking at an r of something like 0.2; a shotgun blast on the side of a barn could have a higher r.

“The study cannot confirm the shift is connected to climate change, but the results are consistent with climate models that predict drier autumns for California in a warming climate, according to the authors.”

In English, “The study doesn’t generate our desired BS, but is consistent with other BS generators.”

Lee Scott
February 5, 2021 6:25 am

So, they are saying that it’s only getting worse because of human-caused global warming. As though it wouldn’t be worse if the warming were natural. Nothing about this study sheds any light on the causes of the longer dry season, only on the results, which would be the same regardless.

Man-made global warming is simply assumed, without question, to be the cause of all climate change. I challenge anyone to demonstrate how the results of man-made global warming would be distinguishable from natural warming.

Reply to  Lee Scott
February 5, 2021 8:32 am

Exactly! Analysis of results is not an analysis of causes.

February 5, 2021 6:29 am

“A dry California riverbed in 2009”

Nothing like up to the minute info.

Andrew

MkeBob
Reply to  Bad Andrew
February 5, 2021 7:54 am

Agreed, but it doesn’t look like a “river bed” to me. It looks like the high end of a reservoir/lake at the end of summer in the California sierra Nevada mountains.

Reply to  MkeBob
February 5, 2021 8:31 am

MikeBob,

In Climate Science, one dry lake bed/dry river bed at any point in the past is as good as one right now.

Does anyone remotely associated with Climate Science even care at this point?

Andrew

kenji
Reply to  Bad Andrew
February 5, 2021 12:42 pm

The crusty old weather dude on KTVU keeps INSISTING CA is in the grips of another “drought” … because the last Sierra snow survey was only 60% of some specific snapshot in time’s “normal”. How ridiculous.

Pro tip for the Weatherdude: Get back to me at the END of the rainy season. Hyping DAILY snapshots in time is utter nonsense. I’ve lived 65 years in CA … and there’s no such thing as a “normal” rainy season or winter. Some heavy precipitation comes early, some come in the middle, and some come late. Just STOP with the naval gazing and DAILY updates. And get back to me with the Reservoir levels at their PEAK in July … and tell me how we are in another of Jerry Brown’s “neverending” CA drought.

eck
Reply to  kenji
February 6, 2021 5:44 pm

You know, if the political hacks had any intelligence, they’d just acknowledge the periodic droughts and do something that would really help the citizens, BUILD MORE RESERVOIRS.

G Mawer
Reply to  MkeBob
February 5, 2021 11:14 am

I agree. Living in the Sierras we see this every year…..drying up lakes! How can one trust a source that can’t even get that part right?

kenji
Reply to  MkeBob
February 5, 2021 12:34 pm

It looks like the upper reaches of Folsom Lake (the poster child of CAGW CA drought) which gets dumped through its spillways each season to ensure some non-native baitfish in the Bay Delta doesn’t get too salty. A Federal Judge demanded it.

Hence … the woeful looking “drought” pics. Ohhhhhhh Mo’mmmmmaaaaaa …

Bruce Cobb
February 5, 2021 6:50 am

I would love to hear them try to explain how warming could possibly cause a delayed rainy season. That would be fun.

Reply to  Bruce Cobb
February 5, 2021 8:03 am

I can show you how the natural wobble of the earth’s axis will shift the not-so-exact dates of seasonal changes…
But that would be grade three natural science, not university graduate sciencery.

Tim Gorman
Reply to  paranoid goy
February 5, 2021 8:19 am

I wonder if the moving magnetic pole has any influence?

kenji
Reply to  paranoid goy
February 5, 2021 12:43 pm

And a certain US Congressman can show you how our military installation on Guam is causing the Island to tip over.

Reply to  kenji
February 5, 2021 12:55 pm

Yeah, but my nose doesn’t have a crust of white stuff under it, and the earth’s axis wobbles slightly. So my snow shrinks and grows, whereas his just blows.

Pamela Matlack-Klein
Reply to  Bruce Cobb
February 5, 2021 11:31 am

Alas, they do not have to explain why warming delays the rainy season, they just have to make the announcement that the rainy season is now delayed by a month because global warming. And lots of ignoramuses believe it.

beng135
February 5, 2021 6:51 am

Mother nature does all kinds of things. What to do? Adapt.

kenji
Reply to  beng135
February 5, 2021 12:47 pm

Good to see another human with his survival instinct intact. Our comfy contemporary urban existence has all but wiped out that instinct. Now, the average citizen cries to their government … “SAVE ME !!!! Aiiiiiieeeeeee”. Hell … they’ll even trade their US Constitutional birthright for the promise of being “saved” by highly paid FAKE Doctor bureaucrats at the CDC

Ron Long
February 5, 2021 6:54 am

It’s a La Niña year, so the snowpack in the Sierra Nevada Mountains started out slow, but several large storm systems recently raised snowpack to 75% of total normal (for the entire season, which still has 2 or 3 months to go). Two more of these large storms and the snowpack will be normal, which is good for a La Niña year. I wonder what variations on a global scale affect the California water/snowpack? Local effects are not illustrative of global climate, which is the issue.

goldminor
Reply to  Ron Long
February 5, 2021 12:38 pm

Surface wind flows have to be considered, imo. This year in particular every time a large AR has formed up and moved eastward into the coast it ends up getting sidetracked by rotational surface winds which then push the AR to the north. There were some great examples of this in December where a major AR had formed up. The local 10 day forecast was for many days of rain, and then surface winds spun all of that north into Washington St and/or the Aleutian Islands and Canada. Here is what that looked like.

earth California Tcw...12 21 20.png
Gordon A. Dressler
February 5, 2021 6:57 am

From the first paragraph in the above article: “The study cannot confirm the shift is connected to climate change, . . .”

That is all you need to know.

Bruce Cobb
Reply to  Gordon A. Dressler
February 5, 2021 7:33 am

They can’t confirm it’s connected to space aliens either.

kenji
Reply to  Gordon A. Dressler
February 5, 2021 12:48 pm

Phew !! At least the Study mentioned Climate Change … otherwise … no more government funding. Right?

Tom in Florida
February 5, 2021 7:39 am

What I couldn’t find was if the end of the rainy season was also later than in the past 60 years.

goldminor
Reply to  Tom in Florida
February 5, 2021 12:47 pm

From my memory, no. Over the last 6 years I have regularly started my garden very early for this area with the exception of last year and this year. Back in the 1970s you would not plant your garden around here until May. That is a bit amazing to me how there can be that much variation. Now I am wondering if the local climate will shift back to a longer winter season in the years ahead.

Michael E McHenry
February 5, 2021 7:42 am

I did a search of the NYT archives last year using key words California, drought, fires…. I got thousand hits for 1920-1980. I was struck by the 1947-1948 rain fall. the last rain was April and the next was February for the north and March for the south

Clyde Spencer
Reply to  Michael E McHenry
February 5, 2021 9:46 am

For the many decades that I lived in the SF Bay Area, it was typical for the Oakland Hills to be green in early-April, and be brown by May 1st.

kenji
Reply to  Clyde Spencer
February 5, 2021 12:57 pm

Still live here … nothing’s changed.

In fact … as a youth growing up playing in the hills of Lafayette, CA in the 1960’s … I witnessed up close and personal the variability of seasonal rainfall. How? I played almost daily in the hills … and some years the grasses and mustard grew way over my head to nearly 6ft tall !! in rare monsoon years. (we made awesome forts in those grasses). The next year … barely 2ft. Some years were spectacular wildflower years … others not so much. Some years, the oaks would sprout more leaves than ever before and whose branches grew in feet, not inches.

When you actually LIVE in nature … computer models, studies, graphs, charts, ipads, and laptops are poor substitutes for actually… experiencing nature. Year after year.

Richard Page
February 5, 2021 7:46 am

I always thought that California’s rainy season was fairly irregular in its start date anyway – sometimes as early as July to September, sometimes later, depending on conditions over the Pacific. Is there a pattern which corresponds with El Nino and La Nina years or is it generally the same?

Doonman
Reply to  Richard Page
February 5, 2021 5:50 pm

When I was young, my mother told me that when she was a child in the 1930’s that the family often had coastal picnics on Thanksgiving Day. I remember saying we should do that too. She said it was always too wet nowadays, but it wasn’t when she was young.

Wharfplank
February 5, 2021 8:02 am

Anybody that knows anything about California knows what causes our droughts. Does CO2 cause blocking Rex highs far out in the Pacific? Just asking…

Jim Whelan
February 5, 2021 8:05 am

I’ve lived in So Cal for over 50 years. Rain sometimes comes late (like it did this year) sometimes early. I haven’t done any scientific analysis but my rule of thumb has been that a late rainy season usually means heavy rain the following nyear and an early season presages a drought.

I any case I notice two things about this “paper”:

  1. the statistically generated slope is minuscule compared to the yearly variation. When I see that kind of discrepancy I conclude that the slope is meaningless.
  2. Graphs of precipitation on a season to season basis does not address the kind of correlation of my, admittedly unscientific, experience. In fact, the yearly data does lend itslef to that kind of analysis. When I see a paper that ignores an important aspect of the data I am led to conclude that the authors were looking for a particular conclusion and chose to omit anything that might contradict that conclusion. In other words BAD science.
Andy Pattullo
February 5, 2021 8:08 am

Similar pattern in North Africa and Europe with rain bands shifting northward or southward with ocean cycles on multi-decades cycles. No evidence this has anything to do with CO2 a trace atmospheric gas necessary for all life on the planet.

Steve Case
February 5, 2021 8:18 am

Here’s a graph of California’s precipitation from NOAA’s Climate at a Glance webpage:
comment image

Their month later claim doesn’t appear to affect California’s precipitation trend since 1895

It will take more than a few minutes to see how well the month later start date claim comports with NOAA’s data. I’m pretty sure NOAA can’t and doesn’t dink with the precipitation data

Michael E McHenry
Reply to  Steve Case
February 5, 2021 8:53 am

It would be interesting to see a La Nina-El Nino chart super imposed on that

TonyG
Reply to  Steve Case
February 5, 2021 10:58 am

FYI: “Image not found or was removed”

Steve Case
Reply to  TonyG
February 5, 2021 1:09 pm

Tony G, For some reason my first post at 8:18 AM didn’t show on my computin’ machine so I thought that maybe I never clicked on the [Post Comment] button, and so I went back to the Postimages dot org and deleted it. Duh! I shouldn’t have done that. I did spend the few minutes to gin up the November Precip data for CA see my post at 9:07 below. And thanks for letting me know.

BTW I see the image on my 8:18 post??? Who knows why the internet and computers do what they do???

If you want to see that image, go to NOAA’s Climate at a Glance, choose; State wide, then California, Precipitation, 12 months ending in December and click on plot trend. You don’t have to choose 1895 – 2020 that’s the default.

Sticking it up Global Warmunist bottoms is fun and easy.

SAMURAI
February 5, 2021 8:20 am

California’s wildfires and water shortages are being caused by insane Leftist eco-wacko’s horrendous forest and water resource mismanagement.

Solutions: Clear the multi-decade accumulated forest deadfall, lease large areas of federal forest lands to timber companies, build more dams and reservoirs, and stop wasting billions of gallons of water reserves every year to save the river smelt..

Joseph Zorzin
Reply to  SAMURAI
February 5, 2021 9:00 am

“…insane Leftist eco-wacko’s horrendous forest and water resource mismanagement…”
And it’s only going to get worse because now they eco-wacko’s think locking up the forests will be part of the solution to climate change. Massachusetts is now home to some of the worst of these eco-wacko’s. At one logging project on state land- the wacko’s chained themselves to log skidders- until arrested.

kenji
Reply to  SAMURAI
February 5, 2021 1:03 pm

You left out overpopulation and 20M+ illegal aliens all competing for fixed resources. I’m no luddite, and times change … but MY generation is dedicated to scolding everyone to do without and use less … while the prior generation was dedicated to BUILDING and DEVELOPING our State’s resources. CA has utterly halted building essential infrastructure and instead calls you piggish if you want a green front lawn.

Those who scold me for living in a Cadillac desert … own the biggest homes and consume the most resources. Such as it is with our cultural elites (as they proudly call themselves)

stinkerp
February 5, 2021 8:47 am

climate scientists have projected it will get shorter as the climate warms

Golly,, Mr. Wizard, how did they do that? Computer models? What else can they do? Project more precipitation as it warms and more drought? Gee wiz, how come they always make the models project bad stuff happening? If they can make them say bad stuff why don’t they make them say good stuff, Daddy-o? Oh, ’cause they’re wet blankets all the time? Don’t they have doctors to fix that?

Last edited 2 months ago by stinkerp
Steve Case
February 5, 2021 9:07 am

Here’s NOAA’s graph of CA Precipitation for November since 1895
comment image

Looks like there was a lot of rain in the ’60s and not so much now, but the overall trend since the 19th century is flat. So the head line:

California’s Rainy Season Starting Nearly A Month Later Than It Did 60 Years Ago

Could have just as well read:

California’s November rain fall was heaviest during the 1960s

And indeed, if you read the full article from the AGU link, it says:

The results show the official onset of California’s rainy season is 27 days later than it was in the 1960s

But no mention of what it was 120 years ago. And besides that, they needed a PhD study to tell them what you can find out on NOAA’s Climate At A Glance in just a few minutes?

McComber Boy
Reply to  Steve Case
February 5, 2021 9:29 am

The article would have been more informative (and therefor pointless) if it would have said “The results show the official onset of Californias’s rainy season is exactly the same as it was in the 1930’s.”

pbh

Steve Case
Reply to  McComber Boy
February 5, 2021 10:37 am

Ha ha ha ha ha ha ha! Good one (-:

Jim Whelan
Reply to  Steve Case
February 5, 2021 9:32 am

“But no mention of what it was 120 years ago” California weather patterns are decades long cycles. Knowing this makes me question any claims that climate can be determined by examining 50 years of weather. It’s clear that hundreds of years are actually required.

Jim Whelan
Reply to  Steve Case
February 5, 2021 9:34 am

I think we’ve seen that over and over and over again. Warming claims are based on statistical analysis that begins with a cold year and end with a warm one or storm frequencies begin when there were few storms and end when there were many.

Richard M
Reply to  Steve Case
February 5, 2021 10:26 am

It looks a lot like the inverse of the AMO. Higher rainfall during the -AMO and less during the +AMO.

kenji
Reply to  Steve Case
February 5, 2021 1:06 pm

Imagine that ! NOAA’s graph coincides with my … “on the ground” (literally, as a natural BOY growing up in the 60’s) … experience. I can empirically confirm the graph from 1955 till today.

Doonman
Reply to  Steve Case
February 5, 2021 6:03 pm

Hey, I can see my Mom’s 1930’s beachside thanksgiving dinners in your graph. Good ‘Ol Mom, she wasn’t lying to me.

Hoyt Clagwell
February 5, 2021 9:10 am

My own recollection of the Los Angeles rainy season is that it always started around the third or fourth week of October. I remember this because it always threatened to ruin trick-or-treating on Halloween. This was in the 60s and 70s. It held true for me up until the last couple years, which statistically means nothing. There’s no way the rainy season has actually moved to December in Southern California, and it usually comes down from the North, so I would think that it isn’t true of Northern CA either. Of course, I’m just using 57 years of actual observations, not models.

Clyde Spencer
Reply to  Hoyt Clagwell
February 5, 2021 9:52 am

My expectations living in the SF Bay Area were that I could expect the first significant rain storm in late-October, followed by nice weather for 2 or 3 weeks, before the Winter rains settled in.

wineglut
Reply to  Hoyt Clagwell
February 6, 2021 8:28 am

Been making wine/growing grapes in Napa Valley for 60 years and charting temps and rainfall on weather stations. My charts echo NOAA graph of precipitation here in the Napa Valley. When I first arrived here farmers were pressured to pick immature crops in September because they feared weeks of rain in October. Some growers had sleds made for harvest should they not be able to get trailers into a muddy vineyard. Now winemakers let the grapes hang until overripe and pick in November. The wines we made in 1970’s averaged about 12% alcohol. Now they average about 14%.

Patrick B
February 5, 2021 9:27 am

“Climate scientists predict wet future for California”
https://www.upi.com/Science_News/2017/07/06/Climate-scientists-predict-wet-future-for-California/1791499368091/

It’s hard to be wrong when your theory predicts all possible outcomes.

February 5, 2021 9:28 am

Ja. Ja. I yold you. Worse drought times are yet to come. Click on my name.

Clyde Spencer
February 5, 2021 9:41 am

The picture looks more like a small, shallow reservoir than a river bed. For river flood waters to get as high as the tree line, the water velocities would be high, and one would expect gravel, not mud, in the channel. I always wonder how trustworthy research is if they play fast and loose with obvious things.

Jim Whelan
Reply to  Clyde Spencer
February 5, 2021 9:53 am

Of course there in the background is a lot of water. If this is a riverbed, it looks like there’s still water flowing in the river and the dry area is an area inundated by a recent flood and recently dried. More likely it is as youj suggest a reservoir which is still at least partially full and the photo is of an area recently uncovered by receeding water wich could just as easily be due to a recent rainy season as to a drought.

lackawaxen123
February 5, 2021 10:08 am

wait … AGW “theory” claims that it will cause MORE rainfall … Droughts are NOT CAUSED by evaporation … and as far as “warming” if another tenth of a degree of warming can “delay” the rainy season then explain the last 100 years … (they can’t of course)

Bill Powers
Reply to  lackawaxen123
February 5, 2021 12:35 pm

We can not expect explanations from people who make statements such as:

The start of California’s annual rainy season has been pushed back from November to December, prolonging the state’s increasingly destructive wildfire season by nearly a month, according to new research.”

As if there were a control board that determines start dates and a control panel that actually dials up the rain.

We stopped “Scienceing” about the time they turned it over to Dr. Frankenstein’s lab assistant ALGORE and the Hollywood documentarians

goldminor
February 5, 2021 12:26 pm

I can recall the changes in the start of the rainy season over the years. In the 1950s the early rains occasionally would start in September, but almost always October would have moderate rains coming in. The real change came in the 1970 from what I recall. I was more aware of this through the 1970s because I spent most of that decade living in the mountains up north. I paid attention to the winter rains in anticipation of experiencing one of those major cyclical flood cycles. Plus I still actively fished for the world famous fighting fish, the steelhead.

I lived along the Klamath river during those years. It was magnificent to stand next to that roaring river when it was flowing strong with the winter rains. You could barely hear your own thoughts over the intensity of sound and vibration when standing nearby the raging river, and it would generally rage ever winter.

Over the last 40 years though the first rains have shifted their timing a good deal, mainly coming in later towards the end of the year, but that is not a consistent pattern. Then there are the dry years where the rains did not start until late December or January; and the truly dry years where there was almost no rain for the entire winter. Then every now and then the big winter would come in with early fall rains which turned heavy later on, such as in 1984/85, 1996/97, 2008/09, and 2016/17. This year for example, it looked like the start of another substantial drought as there was very little rain all the way up to the last several weeks. The rains which did fall over the last several weeks have been minimal though which leaves me wondering if this is the beginning of another drought. I don’t expect the next big wash pattern to hit until around 2026/27. Hopefully, I will still be around to witness that.

kenji
February 5, 2021 12:30 pm

OK. So we need to build MORE Dams … and/or send all the Illegals home. Simple math. Right?

goldminor
February 5, 2021 1:15 pm

Here is one thing which this study does not address, and that is how surface winds can strongly influence ARs as they cross the Pacific. This year, in particular, surface winds have continually steered the rains to the north where they come ashore around Washington, or the Aleutian Islands/Canada. This AR pictured below was from Dec 30th.

earth California Tcw...12 30 20.png
Editor
February 5, 2021 2:01 pm

I’ve added the following chart as an update to the head post …
comment image

w.

Doonman
February 5, 2021 5:32 pm

results are consistent with climate models that predict drier autumns for California

Wait, California has its own climate models? I thought they were global.

Tom Abbott
February 5, 2021 5:52 pm

From the article: “The study cannot confirm the shift is connected to climate change,”

Well, at least they admitted that. They didn’t just assume it was, like most alarmists do.

Tom Abbott
February 5, 2021 6:02 pm

From the article: “What we’ve shown is that it will not happen in the future, it’s happening already,” said Jelena Luković, a climate scientist at the University of Belgrade in Serbia and lead author of the new study. “The onset of the rainy season has been progressively delayed since the 1960s, and as a result the precipitation season has become shorter and sharper in California.”

I see a slight discrepancy here. They are claiming Human-caused Climate Change/Global Warming started causing these “problems” beginning in the 1960’s, but if these scientists would check California’s weather history, they would see that the 1960’s and 1970’s were cold and getting colder. CO2 was not driving this train, at that time.

Remember the famous “Ice Age Cometh” cover on a 1974 cover of Science News magazine?

Captain Climate
February 7, 2021 7:13 am

And probably the same rainy season timing as 100 years ago.

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