Medieval Warm Period seen in western USA tree ring fire scars

Here is just one more indication that despite what some would like you to believe, the MWP was not a regional “non event”.

Top: Mann/IPCC view, bottom historical view

From a University of Arizona press release,

Giant Sequoias Yield Longest Fire History from Tree Rings

California’s western Sierra Nevada had more frequent fires between 800 and 1300 than at any time in the past 3,000 years, according to a new study led by Thomas W. Swetnam, director of UA’s Laboratory of Tree-Ring Research.

This cross-section of a giant sequoia tree shows some of the tree-rings and fire scars. The numbers indicate the year that a particular ring was laid down by the tree. (Credit: Tom Swetnam)

By Mari N. Jensen, UA College of Science March 17, 2010

A 3,000-year record from 52 of the world’s oldest trees shows that California’s western Sierra Nevada was droughty and often fiery from 800 to 1300, according to a new study led by University of Arizona researchers.

Scientists reconstructed the 3,000-year history of fire by dating fire scars on ancient giant sequoia trees, Sequoiadendron giganteum, in the Giant Forest of Sequoia National Park. Individual giant sequoias can live more than 3,000 years.

“It’s the longest tree-ring fire history in the world, and it’s from this amazing place with these amazing trees.” said lead author Thomas W. Swetnam of the UA. “This is an epic collection of tree rings.”

The new research extends Swetnam’s previous tree-ring fire history for giant sequoias another 1,000 years into the past. In addition, he and his colleagues used tree-ring records from other species of trees to reconstruct the region’s past climate.

The scientists found the years from 800 to 1300, known as the Medieval Warm Period, had the most frequent fires in the 3,000 years studied. Other research has found that the period from 800 to 1300 was warm and dry.

“What’s not so well known about the Medieval Warm Period is how warm it was in the western U.S.,” Swetnam said. “This is one line of evidence that it was very fiery on the western slopes of the Sierra Nevada – and there’s a very strong relationship between drought and fire.”

Droughts are typically both warm and dry, he added.

Knowing how giant sequoia trees responded to a 500-year warm spell in the past is important because scientists predict that climate change will probably subject the trees to such a warm, dry environment again, said Swetnam, a UA professor of dendrochronology and director of UA’s Laboratory of Tree-Ring Research.

During the Medieval Warm Period extensive fires burned through parts of the Giant Forest at intervals of about 3 to 10 years, he said. Any individual tree was probably in a fire about every 10 to 15 years.

The team also compared charcoal deposits in boggy meadows within the groves to the tree-ring fire history. The chronology of charcoal deposits closely matches the tree-ring chronology of fire scars.

The health of the giant sequoia forests seems to require those frequent, low-intensity fires, Swetnam said. He added that as the climate warms, carefully reintroducing low-intensity fires at frequencies similar to those of the Medieval Warm Period may be crucial for the survival of those magnificent forests, such as those in Sequoia and Kings Canyon National Parks.

Since 1860, human activity has greatly reduced the extent of fires. He and his colleagues commend the National Park Service for its recent work reintroducing fire into the giant sequoia groves.

The team’s report, “Multi-Millennial Fire History of the Giant Forest, Sequoia National Park, California, USA,” was published in the electronic journal Fire Ecology in February. A complete list of authors and funding sources is at the bottom of this story.

To study tree rings, researchers generally take a pencil-sized core from a tree. The oldest rings are those closest to the center of the tree. However, ancient giant sequoias can have trunks that are 30 feet in diameter – far too big to be sampled using even the longest coring tools, which are only three feet long.

To gather samples from the Giant Forest trees, the researchers were allowed to collect cross-sections of downed logs and standing dead trees, he said. It turned out to be a gargantuan undertaking that required many people and many field seasons.

“We were sampling with the largest chain saws we could find – a chain-saw bar of seven feet,” he said. “We were hauling these slabs of wood two meters on a side as far as two kilometers to the road. We were using wheeled litters – the emergency rescue equipment for people – and put a couple hundred pounds on them.”

To develop a separate chronology for past fires, co-authors R. Scott Anderson and Douglas J. Hallett looked for charcoal in sediment cores taken from meadows within the sequoia groves.

“We can compare the charcoal and tree-ring fire records. It confirms that the charcoal is a good indicator of past fires,” Swetnam said.

Such charcoal-based fire histories can extend much further into the past than most tree-ring-based fire histories, he said. The charcoal history of fire in the giant sequoia groves extends back more than 8,000 years.

Increasingly, researchers all over the world are using charcoal to reconstruct fire histories, Swetnam said. Many scientists are analyzing the global record of charcoal to study relationships between climate, fire and the resulting addition of carbon dioxide to the atmosphere.

Swetnam’s co-authors are Christopher H. Baisan and Ramzi Touchan of the University of Arizona; Anthony C. Caprio of Sequoia and Kings Canyon National Parks in Three Rivers, Calif.; Peter M. Brown of the Rocky Mountain Tree-Ring Research and Colorado State University in Fort Collins; R. Scott Anderson of Northern Arizona University in Flagstaff; and Douglas J. Hallett of the University of Calgary in Alberta, Canada.

The National Park Service, the U.S. Geological Survey, Mountain Home Demonstration State Forest and Calaveras Big Trees State Park provided funding.

h/t to Dr. Leif Svalgaard

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joe

This is exactly, what the global warming theory predicts…?

B. Smith

I know Three Rivers quite well as my brother and mother lived there for many years. Anyone who has been into the park and seen these incredibly large, ancient trees close up could not help but come away humbled and more than a bit awestruck. It’s comforting to know those magnificent forests can survive harsh changes in climate.
Those tree rings provide pretty hard evidence that the MWP extended at least as far as the western USA. Evidence that’s hard to refute, I should think.
I wonder what those same rings would say about temperatures over the past 25-30 centuries?

Ian McLeod

I wonder if it is possible to calibrate other long living trees like the bristle-cone pine with the sequoia.
Does anybody know if the sequoia tree diverges like bristle-cone pine trees do with respect to recent ground-based temperature readings, say for the past 30-year period?

kim

The Ents are moving.
===========

Jimbo

“…carefully reintroducing low-intensity fires at frequencies similar to those of the Medieval Warm Period may be crucial for the survival of those magnificent forests, such as those in Sequoia and Kings Canyon National Parks.”
Yet the alarmists would blame more frequent fires in Sequoia and Kings Canyon National Parks on global warming. I am all too aware that some plant species do better after they have been subjected to fire and some species are dependent on fire occuring at some time in their life cycles.
“America’s most-cherished legacy tree, the giant Sequoia, is known as a “fire-dependent” species because it requires the heat effects of fire in order to prepare the soil and release the seeds of the next generation of sequoias.”
http://www.fireecology.org/research/USFS_fire_dependent.html
More here:
http://www.nifc.gov/preved/comm_guide/wildfire/fire_6.html
http://findarticles.com/p/articles/mi_m1016/is_2_108/ai_89023208/

Jimbo

I should have said:
“Yet the alarmists would blame more frequent fires in Sequoia and Kings Canyon National Parks on man made global warming.”

FergalR

Happy st. Patrick’s day all!
I must say that I believe the temperature record has been perverted for twisted anti-human reasons and considering the damage the aforementioned has done we should all be delighted that, our expense, the likes of the UN’s carbon-trading mastermind; the haggard Dr. Graciela “my head looked vaguely human until I had it horrifically cut up in bits at your expense” Cichilnisky had loads of our cash with which to deform their faces.
http://images.google.ie/images?um=1&hl=en&tbs=isch%3A1&sa=1&q=graciela+chichilnisky&btnG=Search&aq=f&aqi=&aql=&oq=&gs_rfai=&start=0
Why grow old gracefully when you can spend other’s money making you look like something out of a horror movie?

Ian McLeod

Kim,
Perhaps the Kings Canyon National Parks is where the Entwives were lost.

Claude Harvey

But how did they know which trees were the “fire detector trees”? We know from the most famous tree ring studies that some trees are “temperature trees” and others are not. Researchers had to cull through thousands of tree ring records to find those 10 or 12 temperature trees that produced the hockey stick. Apparently, toward the end of the 20th century there were no longer ANY temperature trees. How can finding “fire detector trees” be so simple?
(I’ll save Andrew the trouble here and mark my comments as “sarcasm”)

DocMartyn

They are not really thicker rings, nor is there any evidence of fire damage, after the data is adjusted it is quite clear that nothing happened until 1968.

savethesharks

Fascinating. Those trees are just magnificent.
Chris
Norfolk, VA, USA

Sean

The odd thing is the periodicity of the fires, every 3-10 years for an average around 7. It’s also interesting that the EAST coast has intense rain and snow precipitation about every 7 years. So while the west coast dries out and burns up, the east coast gets dumped on and digs out. At least we have an idea where all that moisture went during the drought. At least one climate scientist, Judith Curry, understands its important to understand the ocean cycle’s affect on climate and weather.

DesertYote

The normal weather regime for California is wet winters and dry summers. Fires, by themselves are not an indication of drought. They could indicate an unusual amount of lightning. Even during wet years, summer lightning will cause significant fires. I am always a bit suspicious of the Hot-Dry / Cold-Wet view of weather and reports that try to support it. The usual pattern as indicated by the palaeoclimatological record, is Hot-Wet / Cold-Dry. But California, being a western coast, has a unique climate pattern. I would be interested in finding out what the evidence is for unusual drought conditions. Can anyone help educate me?

I thought that the AGW dogma wrote the MWP off as a northern hemisphere issue, not just a “regional” issue. If that is the case, then showing American data with a MWP doesn’t touch this claim. Am I wrong somewhere?

Layne Blanchard

How would one region of the earth remain perpetually MUCH warmer than the rest for Centuries? Bulls..t!

4 billion
Geoff Sherrington

If oxygen isotopes fractionate in the low energy processes when water evaporates, as is alleged, maybe carbon isotopes fractionate in the high energy processes of charcoal formation. Any references known?

Lord Jim

4 billion (18:27:31) :
Evidence of regional cooling during the MWP.
“Medieval Warm Period Record of the Week
Was there a Medieval Warm Period? YES, according to data published by 811 individual scientists from 483 separate research institutions in 43 different countries … and counting! This issue’s Medieval Warm Period Record of the Week comes from Southwest Greenland. To access the entire Medieval Warm Period Project’s database, click here.”
http://co2science.org/

Amino Acids in Meteorites

is anyone else to the point where seeing the hockey stick makes you nauseated?

Come on people now!!!!!!!
Human beings have been living in the Sierras for 10,000+ years. It is well-known and well-documented that human beings everywhere and in CA, too, set fires to modify the landscape for survival purposes. I venture that EVERY fire scar Swetnam et al looked is from an anthropogenic fire!!!!
Do you blame car accidents on climate change????? Number of baseball games?????
This is a human-mediated, human-caused phenomenon being investigated. It has nothing, zero, nada to do with climate. Sorry all you desperately seeking Medieval Warm Period evidence folks — this ain’t it.
The article says, “Since 1860, human activity has greatly reduced the extent of fires.” That’s just backasswards. Human activity, i.e. anthropogenic fire, has declined ever since those responsible for setting the fires were wiped out by Old World diseases and Euro-American invaders.
The Americas were not devoid of people when Columbus landed. Even he didn’t claim that. It is thought that ~50,000,000 humans lived in the Americas in 1492. Many were in CA, and like people everywhere, they controlled the fire regimes.
Look, I know it’s not what you were taught in the horrifically bad public school you attended. But it’s a fact, nonetheless. Setting fire is as much a part of being human as opposable thumbs. Chances are fires have been annual in the Sierras for thousands of years. Swetnam is a deluded racist historical revisionist cultural bigot crappy scientist if he doesn’t think that’s so.
Come on folks. Leif, tell ’em. You can’t take an anthropogenically caused phenomenon and detect micro climate change in it. That’s goofy. I’m not saying there was no MWP. All I’m saying is fire scars in a human-mediated cultural landscape are not climate proxies!!!!!!!!!

Amino Acids in Meteorites

4 billion (18:27:31) :
The MWP was not warm the entire time.
Looking at the smoothed graph it would appear that it was. Do you know what smoothing is?
The raw data shows temps were up and down during those years.
But the data also shows the warm years were much warmer than warm years now in this two past decades—supposedly the warmest decades on the last 1000 years.
“Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium …””

kim

Ian 18:04:30
Cherchez les femmes.
==========

Doug Badgero

Ian McLeod (17:55:06)
“I wonder if it is possible to calibrate other long living trees like the bristle-cone pine with the sequoia.”
Someone who knows more than me about this may correct me but…….As I understand it, bristle-cones are strip bark trees and cannot be used as temperature proxies because of the way they grow. They do not grow in concentric circles. One area will die and cause growth favorably in another area. That is why the trunk cross sections are so oddly shaped. There are simply to many covariants to tease a temperature signal out.

Ian McLeod

Kim…lol…double entendre

Roger Knights

@Mike D: But if humans were setting fires for millennia, there should have been an equal number of tree ring damage before and after the MWP — and there wasn’t.

Charles Platt

The lower graph that heads this piece seems to have absolutely nothing to do with the university press release.
The lower graph is labelled “Climatic Changes in Europe.” The tree ring study was done in the western Sierra Nevada, in the United States. How do you expect to convince even open-minded and receptive people (such as myself) when you do this kind of thing?
Moreover, the graphs are not properly sourced. “IPCC Hockey Stick,” reproduced from where? “Historical view,” measured how, reproduced from where?
Also the university press release makes no estimates whatsoever about the actual temperature during the medieval warm period, only that it was “warm and dry.”
You have more than enough evidence for skepticism without presenting this kind of sloppy, misleading material.

theduke

There is a tree in Yosemite called the fallen giant. About 20 years ago, I bought one of those wide view disposable cameras to use on trip to Yosemite. I took a picture of my wife standing next to the trunk of the Fallen Giant. The photo is roughly 3×8 wide. I sometimes take the album out and say to people, “my wife is in this photo. Can you find her?” Without exception, people are unable to locate her because they don’t comprehend the scale of the human vs the tree.

Ian McLeod

Doug Badgero,
You are correct about those knotty bristle-cone pines, I agree with everything you said, but unfortunately, some still use them as a temperature proxy and they happen to be one of the most divergent trees used.

Amino Acids in Meteorites

Mike D. (18:55:01) :
Do forest fires ever start naturally?
I have heard of native Indians starting prairie fires. But not too much about forest fires.
Could you provide a link or a book title that shows that American Indians started forest fires?

Amino Acids in Meteorites

Mike D. (18:55:01) :
And if American Indians did start forest fires why did they start more of them during the Medieval Warm Period, 800 to 1300, than at any other time?

theduke

Here’s a photo that approximates the one that I took of my wife, although mine was better (of course!)
http://htmlhelp.com/~liam/California/Yosemite/MariposaGrove/FallenMonarch1.jpg
The post by Mari Jensen is right on. There is much to be learned from these trees, as opposed to, say, Yamal as interpreted by Briffa.

Wren

Puzzling Graphs
This article was supposed to be about the findings of a study titled “Multi-Millennial Fire History of the Giant Forest, Sequoia National Park, California, USA. I was puzzled by the graphs at the beginning of the article, so I went to the study for clarification. But I did not find these graphs in the study.

rbateman

savethesharks (18:10:40) :
I have 1/2 dozen of them growing in my yard. They love to be planted in soil that has been cooked by a hot fire. No fertilizer. Just Sun, C02, water and raw mineral soil. The tops of them follow the sun, bending up to 15 degrees.

Mike D.
“It is thought that 50,000,000 people lived in the Americas before 1492..”
I had an anthropology professor, 40 years ago, who asked just that question. But more specific to the size of the “Native American” population prior to the “white man” coming to America.
He got all sorts of answers, many in the multi millions. He then laid down the bomb: “Prior to the ‘white man’..coming to America, there NEVER was more than 500,000 in habitants in the whole of North America, and likewise in South America. That’s what we will prove this semester!”
He then went on TO prove it, by studying the “remains” of the ancient groups, and reviewing either their “hunter gatherer” life style or their LIMITED agriculture.
To claim that the sequoia’s, WITH NO TRACE OF MAN in the area going back 1500, 2000 years… were harmed by fires set by man is at BEST, ludicrous. At worse, a facicious, ficticious untruth.

B. Smith

Mike,
The authors are correct. Forestry service conservation practices altered the natural, low intensity burn offs that occurred in regularly over the centuries in the Sierra and elsewhere. The Forestry Service thought forest fires were to be fought and extinguished immediately. That practice allowed the unprecedented build up of tinder-dry fuel over decades. Forest fires became conflagrations and we lost more timber than we saved. It wasn’t until relatively recently that the Forest Service came to understand that nature’s way was the best way to conserve our forests.
I don’t know of any reason why the prehistoric hunter-gatherers who inhabited the western US would have started fires in the Sierra or other western forests, unlike their agriculturally-based slash and burn relatives in southern Mexico, Central and South America.

Pascvaks

Ref – Mike D. (18:55:01) :
“Come on people now!!!!!!!
“Human beings have been living in the Sierras for 10,000+ years. It is well-known and well-documented that human beings everywhere and in CA, too, set fires to modify the landscape for survival purposes. I venture that EVERY fire scar Swetnam et al looked is from an anthropogenic fire!!!!”
________________________________
On this issue I think you may be a tinnsy winnsy wrong. Fires for clearing, yes. Accidental fires, yes. Fires in the grove of the Gods set deliberately to tick the “The Great Spirit” and his friends off and bring famine and disease to you and your tribe? No way Jose! The only people crazy and dumb enough to ever try something that stupid were born in the last 25 years and, fortunately, none of them have been successful -to date.

In other places in the world (eg the Sahara), regions of the world became warmer and wetter during the MWP. But in the American West, it became drier, which suggests that during warmer periods, La Nina predominates in the Pacific.

Wren

4 billion (18:27:31) :
The MWP was not warm the entire time.
Looking at the smoothed graph it would appear that it was. Do you know what smoothing is?
The raw data shows temps were up and down during those years.
But the data also shows the warm years were much warmer than warm years now in this two past decades—supposedly the warmest decades on the last 1000 years.
“Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium …””
————————
I believe that’s from the NRC report that the American Statistical Association discusses in a newsletter. The newsletter also had this to say about the NRC’s findings”
‘Despite all this evidence, the NRC report phrased its conclusions cautiously, concluding it was no more than “plausible” (2:1 odds in favor) that the temperatures of the last few decades were unprecedented in recorded history.’
http://www.amstat-online.org/sections/envr/ssenews/ENVR_9_1.pdf

Pascvaks

Pascvaks (19:43:16) :
Clarification –
“Fires for clearing, yes.” But NOT in the Grove of The Giants! There’s not a whole lot of great sunlight for your pumpkins and squash.

Mike D
The Americas were not devoid of people when Columbus landed. Even he didn’t claim that. It is thought that ~50,000,000 humans lived in the Americas in 1492>>
Wow. Columbus landed in 1492 and did a population survey across a few million square miles of continent? How’d he do it? Stand in the crows nest at the top of the mast of one of his ships with a spyglass and count them? Not to mention that 50,000,000 people could not possibly feed themselves as a hunter gatherer society. Also not to mention that primitive tribes who lived off the land were skilled outdoorsmen which would include knowing how to control a campfire. If they weren’t skilled outdoorsman… well then they were dead.

Samuel

“Droughts are typically both warm and dry, he added”
Is this what they call dry humour?

geo

What is the accuracy range of dating tree rings this old? 1 yr? 10? 25? 50? 100? What?
I’m more and more wondering if the hockey stick disappeared the MWP in large part because of inaccurate dating of multiply proxies cancelling each other out.

John F. Hultquist

Picture Gallery of Trees and Tree Rings (Univ. of Tenn., Knoxville)
http://web.utk.edu/~grissino/gallery.htm

Amino Acids in Meteorites

Mike D. (18:55:01) :
~50,000,000 humans lived in the Americas in 1492. Many were in CA, and like people everywhere, they controlled the fire regimes.
I don’t think either one of these facts are correct, especially about ‘Many were in CA’.
Would you tell me the source?

Amino Acids in Meteorites

Wren (19:34:00) :
Are you feeling ok Wren? Do you have a fever or anything?

kuhnkat

Joe,
yes, global warming says this type of event can happen.
Unfortunately the Models that purportedly embody the physics that AGW is based upon are incapable of matching the Little ice Age, Medieval Warm Period, Roman Optimum, and all other extreme temp events in the past!!!
Now, saying something can happen in a certain way and SHOWING HOW it can happen in a certain way is the difference between gossips and scientists.

Amino Acids in Meteorites

Max Hugoson (19:39:17) :
Max,
I had learned something similar, that the population of native Indians west of the Mississippi was ~250,000. Some of the tribes, apparently, had only about 400 people. And some small tribes were wiped completely out in warfare with other tribes. The population couldn’t have been in the millions.
I think Mike D. is just rambling some sarcasm.

Mike D. (18:55:01) :
“Human beings have been living in the Sierras for 10,000+ years. It is well-known and well-documented that human beings everywhere and in CA, too, set fires to modify the landscape for survival purposes. I venture that EVERY fire scar Swetnam et al looked is from an anthropogenic fire!!!!
This is a human-mediated, human-caused phenomenon being investigated. It has nothing, zero, nada to do with climate. That’s just backasswards.”
================================================
‘Every scar’ would be wrong as it is proven that lightning can produce forest fires, and this is a natural recurring phenomenon.
Also, your presumed conjecture that humans would be using fire to clear land in forests does not seem consistent with my understanding of how we used fire in the past to create farmland, our ancestors would have more likely set fire to fields.
And if it would be your assertion that fires set in fields would spread to forests…well, then wouldn’t the forests have to be dry and susceptible to lightning induced fires for this to occur? Can you imagine the difficulty in farming land with fallen trees, and with some trunks still extending to the heavens blocking sunlight?
“That’s just backasswards” – have to agree from my point of view.
You’re trolling, right?

Amino Acids in Meteorites

davidmhoffer (19:54:41) :
Wow. Columbus landed in 1492 and did a population survey across a few million square miles of continent? How’d he do it? Stand in the crows nest at the top of the mast of one of his ships with a spyglass and count them?
………………………………………………………………………………………………………………
No, he didn’t actually get the real data. It was estimated, and homogenized, using a NASA grid model. That’s why the number is artificially high. He used a more heavily populated area to start with instead of those sparser forest and mountain areas. He just figured that it would all come out in the wash the same as if he used the real data.