From the University of Arizona, one wonders how such a thing could happen when CO2 was at “safe” levels. They are using bristlecone pines again, which may very well be a better proxy for rainfall than for temperature. At least there was no competition bias from sheep ranching then. It seems they also confirmed a drought in the medieval warm period in the 12th century.
UA scientists find evidence of Roman period megadrought
A new study at the University of Arizona’s Laboratory of Tree-Ring Research has revealed a previously unknown multi-decade drought period in the second century A.D.
IMAGE: Dendrochronologists extract a small, pencil-shaped sample of wood from a tree with a tool called an increment borer. The tiny hole left in the tree’s trunk quickly heals as the…Click here for more information.
Almost nine hundred years ago, in the mid-12th century, the southwestern U.S. was in the middle of a multi-decade megadrought. It was the most recent extended period of severe drought known for this region. But it was not the first.
The second century A.D. saw an extended dry period of more than 100 years characterized by a multi-decade drought lasting nearly 50 years, says a new study from scientists at the University of Arizona.
UA geoscientists Cody Routson, Connie Woodhouse and Jonathan Overpeck conducted a study of the southern San Juan Mountains in south-central Colorado. The region serves as a primary drainage site for the Rio Grande and San Juan rivers.
“These mountains are very important for both the San Juan River and the Rio Grande River,” said Routson, a doctoral candidate in the environmental studies laboratory of the UA’s department of geosciences and the primary author of the study, which is upcoming in Geophysical Research Letters.
The San Juan River is a tributary for the Colorado River, meaning any climate changes that affect the San Juan drainage also likely would affect the Colorado River and its watershed. Said Routson: “We wanted to develop as long a record as possible for that region.”
Dendrochronology is a precise science of using annual growth rings of trees to understand climate in the past. Because trees add a normally clearly defined growth ring around their trunk each year, counting the rings backwards from a tree’s bark allows scientists to determine not only the age of the tree, but which years were good for growth and which years were more difficult.
IMAGE: A cross section of wood shows the annual growth rings trees add with each growing season. Dark bands of latewood form the boundary between each ring and the next. Counting…Click here for more information.
“If it’s a wet year, they grow a wide ring, and if it’s a dry year, they grow a narrow ring,” said Routson. “If you average that pattern across trees in a region you can develop a chronology that shows what years were drier or wetter for that particular region.”
Darker wood, referred to as latewood because it develops in the latter part of the year at the end of the growing season, forms a usually distinct boundary between one ring and the next. The latewood is darker because growth at the end of the growing season has slowed and the cells are more compact.
To develop their chronology, the researchers looked for indications of climate in the past in the growth rings of the oldest trees in the southern San Juan region. “We drove around and looked for old trees,” said Routson.
Literally nothing is older than a bristlecone pine tree: The oldest and longest-living species on the planet, these pine trees normally are found clinging to bare rocky landscapes of alpine or near-alpine mountain slopes. The trees, the oldest of which are more than 4,000 years old, are capable of withstanding extreme drought conditions.
“We did a lot of hiking and found a couple of sites of bristlecone pines, and one in particular that we honed in on,” said Routson.
To sample the trees without damaging them, the dendrochronologists used a tool like a metal screw that bores a tiny hole in the trunk of the tree and allows them to extract a sample, called a core. “We take a piece of wood about the size and shape of a pencil from the tree,” explained Routson.
“We also sampled dead wood that was lying about the land. We took our samples back to the lab where we used a visual, graphic technique to match where the annual growth patterns of the living trees overlap with the patterns in the dead wood. Once we have the pattern matched we measure the rings and average these values to generate a site chronology.”
“In our chronology for the south San Juan mountains we created a record that extends back 2,200 years,” said Routson. “It was pretty profound that we were able to get back that far.”
IMAGE: Doctoral candidate Cody Routson of the environmental studies laboratory at the University of Arizona’s department of geosciences scrambles up a mountain slope to sample a bristlecone pine tree. Click here for more information.
The chronology extends many years earlier than the medieval period, during which two major drought events in that region already were known from previous chronologies.
“The medieval period extends roughly from 800 to 1300 A.D.,” said Routson. “During that period there was a lot of evidence from previous studies for increased aridity, in particular two major droughts: one in the middle of the 12th century, and one at the end of the 13th century.”
“Very few records are long enough to assess the global conditions associated with these two periods of Southwestern aridity,” said Routson. “And the available records have uncertainties.”
But the chronology from the San Juan bristlecone pines showed something completely new:
“There was another period of increased aridity even earlier,” said Routson. “This new record shows that in addition to known droughts from the medieval period, there is also evidence for an earlier megadrought during the second century A.D.”
“What we can see from our record is that it was a period of basically 50 consecutive years of below-average growth,” said Routson. “And that’s within a much broader period that extends from around 124 A.D. to 210 A.D. – about a 100-year-long period of dry conditions.”
“We’re showing that there are multiple extreme drought events that happened during our past in this region,” said Routson. “These megadroughts lasted for decades, which is much longer than our current drought. And the climatic events behind these previous dry periods are really similar to what we’re experiencing today.”
The prolonged drought in the 12th century and the newly discovered event in the second century A.D. may both have been influenced by warmer-than-average Northern Hemisphere temperatures, Routson said: “The limited records indicate there may have been similar La Nina-like background conditions in the tropical Pacific Ocean, which are known to influence modern drought, during the two periods.”
Although natural climate variation has led to extended dry periods in the southwestern U.S. in the past, there is reason to believe that human-driven climate change will increase the frequency of extreme droughts in the future, said Routson. In other words, we should expect similar multi-decade droughts in a future predicted to be even warmer than the past.
###
Routson’s research is funded by fellowships from the National Science Foundation and the Science Foundation Arizona. His advisors, Woodhouse of the School of Geography and Development and Overpeck of the department of geosciences and co-director of the UA’s Institute of the Environment, are co-authors of the study.
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You obviously don’t want to answer the question, because the answer is uncomfortable. But no matter. You know and I know. Somebody who doesn’t know the difference between compounds and molecules isn’t qualified to make assessments about the state of climate science.
And one annoying thing I’ve noticed about you from your posts in multiple threads:
You really like going into third person mode a lot. “Robert Bertino is this”, “Kevin MacDonald is that”. Is that supposed to be more of an insult than saying it directly to our faces? lol
Robert Bertino repeatedly claims that I don’t know the difference between a molecule and a compound. Having spent a 30+ year carreer working with many other engineers designing, calibrating and repairing weather related instruments, I could assure the young Mr Bertino [if I were responding to him] that I have probably forgotten more than the youngster has ever learned up to this point.
Now, if someone wanted to provide a reasonable criticism of me that I would happily agree with, it would be that I get some amusement from pushing Bobby’s buttons and causing him to furiously post one impotent, demanding comment after another, as he has been doing. IMHO Bobby needs a girl friend. The kind he doesn’t have to inflate.☺
Smokey says:
“Glad you asked. Here is a global map of interactive charts showing the global impact of the MWP. Put your cursor on any of the charts for an expanded version.”
That is a map that shows various regional warming trends that aren’t globally synchronous and, thus, is’t actually what I asked for; a chart that shows global temperatures, within the Holocene, that are warmer than today.
Smokey says:
“And here is a good article that debunks the nonsense that the MWP wasn’t a global event.”
Nice straw man, but I haven’t been arguing for a globally asynchronous MWP, only that it wasn’t warmer that the last 100 years.
Smokey says:
“And to repeat: there were global warming events prior to the MWP that were warmer than the MWP, and when CO2 was very low. And there were global glaciations when CO2 was very high. The logical conclusion: current temperatures are a function of natural variability, not changes in CO2.”
Moving the goal posts now? Here is your earlier null hypothesis; ““If one or more of the parameters of the Holocene were exceeded, then the null hypothesis would be falsified.”” Do you now accept that this has been falsified and, if not, will you ever actually provide evidence for a time in the Holocene when it was actually warmer that it is now?
Kevin MacDonald,
You still do not understand the null hypothesis! Amazing. I’m giving up on you since you can’t grasp the concept. The Holocene covers the past ten millennia, not just the MWP. There was the Minoan Optimum, the Roman Optimum, etc., which were warmer than the MWP. I’ve posted dozens of charts, including several charts of Holocene temperatures based on peer reviewed data from major journals that are accepted everywhere – and you still refuse to accept any of them [babbling instead about a mythical “Lhehel”]. Your mind is made up and closed tight. All you’re doing is arguing for the sake of argument, like your junior sidekick Bobby.
Since you refuse to accept any of the ample verifiable, empirical, peer reviewed evidence I’ve provided, it’s clear that your true religious faith in CAGW pseudo-science is unshakable. You’re no different from a member of Leon Festinger’s Seekers: the flying saucer didn’t arrive as predicted. But does that mean there’s no flying saucer? Of course not! Mrs Keech just made a new prediction, and the flying saucer will arrive then. True Believers in CAGW are no different. Their predictions are wrong, but just you wait, that runaway global warming is right around the corner. As if.
This thread has been fun, but trying to educate lunatics is a Sisyphean task [I note the moon is full]. So I’ll be moving on to a current thread; this one is almost a week old. True Believers can stick around here. Mrs Keech’s acolytes didn’t abandon her when the flying saucer failed to arrive, either.
^and your criticisms of Kevin are unfair. You post your stuff, saying its accurate and factual, while at the same time, Kevin posts his and you dismiss them as “fantasy charts” without actual delving into any specifics.
“The kind he doesn’t have to inflate.☺”
you really convince me of your 30+ years of experience when you make comments like this.
Exactly what part of the evidence of warmer temperatures during the Holocene than Present did you not understand?
The lack of it. None of Smokeys graphs show global temperatures higher than modern times.
The graphs depitct higher temperatures than Present, so how are they not “global temperatures higher than modern times”?
They are not global in scope, they are
measurements from a single geographic point.
^Kevin is right. Global warming is a global phenomena, measurements from one point don’t change anything. Some areas will get colder, others hotter, but what we will see is a net temperature rise globally. Systems that trap more heat energy in them have more extreme (in variation) climates.
D. Patterson is correct. There are numerous world wide proxies showing that the Medieval Warming Period was in fact global:
http://www.ncasi.org/publications/Detail.aspx?id=3025
http://climateaudit.org/2007/11/18/loehle-proxies
http://wattsupwiththat.com/2010/09/28/loehle-vindication
http://www.worldclimatereport.com/index.php/2008/02/11/a-2000-year-global-temperature-record
http://wattsupwiththat.com/2011/11/10/new-study-shows-temperature-in-greenland-significantly-warmer-than-present-several-times-in-the-last-4000-years
But not warmer than current global temperatures (Loehle submtted revised figures when errors exaggerating the MWP were discovered in the original) and that is rather the point.
Aside from areal sensing measurements made from Earth orbit by satellite instrumentation for example, the vast majority of direct and proxy temperature measurements are “from a single geographic point.” Excluding such “a single geographic point” from the data record would in effect exclude nearly all of the modern instrumental records other than remote sensing systems such as aerial and space remote sensing measurements. That would make no rational sense. Did you perhaps mean to say the charts are not global in scope because they were not measurements from both hemispheres or multiple continents around the globe?
If so, it appears you are deceived by the talking points taken from the false information provided by Grist in its “How to Talk to a Climate Skeptic: Responses to the most common skeptical arguments on global warming” website.
So, why then do you deny all of the evidence of the climate Optimums reported to have occurred during the Holocene and Pleistocene with higher than Present temperatures in the Northern Hemisphere, Southern Hemisphere, Eastern Hemisphere, Western Hemisphere, and all or nearly all continents?
Another straw man, I’m not arguing that any data set be excluded, but pointing out that unless they are combined with data sets from other regions a single data set is useless for inferring global temperatures.
Why are you using Loehle as a false strawman argument, when the evidence for the earlier Holocene temperatures greaer than Present has nothing to do with Loehle?
You were not presented with a strawman argument. You made the strawman argument when you falsely wrote: “None of the ones you have linked to so far do, most of them show Vostock or GISP2, two locations in the Arctic – hardly global – and the only other graph with a source is Lhehel 2007 which was subsequently ammended when it was discovered that it exaggerated the MWP.” You misspelledd Vostok as “Vostock”, and you falsely said the Vostok ice core came from the Arctic, which is of course at the top of the Northern Hemisphere. In the real world, the Vostok ice core came from the Antarctic at the bottom of the globe in Eastern Antarctica and at the opposite side of the world from the GISP2 ice core in the continent of Greenland. Although an argument may be made the two ice cores are not perhaps representative of the global temperature trend for the entire Earth, it is a total lie arising either from careless neglect or deliberate intent to misrepresent the two ice cores as coming only from the Arctic, which is in just the Northern Hemisphere. It was because of this glaring falsehood upon your part about the Vostok ice core which made it necessary for me to attempt to determine exactly what you do and do not mean in your words and phrasing when you use such terminology as “They are not global in scope, they are measurements from a single geographic point.” After all, you have just demonstrated your inability to tell the difference between the top and bottom of the globe by erroneously claiming the Vostok ice core project was in the same Arctic region as the GISP2 project in Greenland.
The Earth was warmer overall at times during the Medieval Warm Period (MWP), but even if you exclude each and every report about the MWP, you still have to deny the evidence of higher temperatures than Present in each of the preceding global climate Optimums as well. You certainly are not going to have any success at denying those reports by falsely pretending there is no evidence of such temperatures at widely separated locations on many continents in both hemispheres of the Earth.
D. Patterson says:
“You were not presented with a strawman argument.”
Yes I was, you claimed I was arguing for the exclusion of certain proxies or data sets from the temperature record when I was in fact arguing that individual proxies are of no use in inferring global in and of themselves. Mischaracterisation of an opponents argument is the definition of straw man
D. Patterson says:
“You made the strawman argument when you…falsely said the Vostok ice core came from the Arcti”
An error on my part, for which I apologise, but not a straw man as it in no way misrepresents my opponents case – that current temperatures fall within the parameters of the Holocene – where Vostok actually is (or how its spelled) is not important, the fact remains that we can’t infer global temperatures from the temperatures at a single point on the globe we have to combine the various proxies to give us fuller coverage and none of the graphs Smokey linked to do this.
D. Patterson says:
The Earth was warmer overall at times during the Medieval Warm Period (MWP)”
There is no evidence to support this assertion.
D. Patterson says:
“You certainly are not going to have any success at denying those reports by falsely pretending there is no evidence of such temperatures at widely separated locations on many continents in both hemispheres of the Earth.”
Again, I’m not arguing that the evidence does not exist, I am arguing that no given proxy, in isolation, can be used to infer global temperatures, proxies have to be combined, thusly, with others from different regions to show the global picture. Nobody on this thread has linked to a multi proxy data set showing global temperatures during the holocene higher than today’s.
So, if you understand a strawman argument is the “mischaracterization of an opponents argument,” then why do you mischaracterize my asking you whether or not it was true you DID NOT mean to say it illogically as a strawman argument? Notice I made no assumption you actually meant what you could have ambiguously wrote, But instead asked you to clarify that you did not mean the literal interpretation of what you wrote. I extended you the courtesy of NOT interpreting your writing contrary to your intent, and yet your response is to wrongly attempt to claim I did so to create a strawman argument.
You claim that you did not make a strawman argument because “it in no way misrepresents my opponents case….” On the contrary, your error did misrepresent Smokey’s case, by conflating two temperature records into just the Arctic region of the Northern Hemisphere, deceiving any uninformed readers into believing Smokey’s information did nothing whatsoever to represent the temperatures outside of the Arctic and the Northern Hemisphere. The reality on the other hand is a temperature record indicating warmer temperatures at the top and bottom of the world, the Arctic and the Antarctic, the Northern Hemisphere and the Southern Hemisphere. As I wrote before, it may be possible to argue having only two locations in the world at opposite ends of the Earth does not provide full coverage, it makes a world of difference in significance when the two measurements come from opposite sides of the world. Although these two measurements omit coverage of the temperate latitudes and the tropical latitudes, they do indicate the two measurements are more consistent with a wamer world in which these intermediate temperature measurements are absent from the charts than it does a world in which the world was not warmer in the same two locations regardless of whatever the intermediate latitudes could have been. Consequently, your error did result in a strawman argument by denying the fact that having the two measurements at the planet’s opposite poles eliminated the possibility the warmer temperatures occurred only in the Arctic of the Northern Hemisphere.
There is no evidence to support this assertion.
You were supplied with evidence that comes from every continent on the Earth, and still you deny this after making the error of assuming the Vostok project was in the Arctic. Perhaps you would care to explain how each of these points of measurement from continents all around the Earth are not satisfactory?
It appears you are making a false statement. Smokey posted a link to a website displaying numerous sites for such temperature data sets. Let us see you refute each of those sources, before you make such sweeping statements denying their existence. Furthermore, other posters posted other individual datasets obtained in different parts of the world. Then there are the various sources not yet mentioned in the thread for the Medieval Warm Period (MWP). Beyond the MWP there are also the sources for the other climate Optimums which you have not even made any effort to address, whether or not they were mentioned in this thread.
You can begin by refuting the individual sources in Africa and South America for the MWP.
D. Patterson says:
“You can begin by refuting the individual sources in Africa and South America for the MWP.”
I’ve already done this, that was the point of the multi-proxy graph I linked to; it shows that the warming events depicted in the individual proxies were regional rather than global in scale, if they were globally synchronous then that would show in multi-proxy reconstructions as a temperature point higher than current levels.
D. Patterson is correct when he states that there is evidence that the Earth was warmer overall at times during the Medieval Warm Period. Dr. Loehle used eighteen different (non-tree ring) proxies, all of them peer-reviewed, and all showing MWP temperatures as high or higher than present global temperatures. Please see the links in my previous post.
There is globally synchronous multi-proxy evidence showing unequivocally that prior warm periods were in fact warmer than today’s temperatures. The IPCC showed this in AR-1:
http://jonova.s3.amazonaws.com/guest/de/temps-ar1.jpg
Since then there has been a concerted effort by some to rewrite the geological evidence. That effort has not gained traction because the multi-proxy evidence from multiple ice cores in both hemispheres shows definitively that the earth has been warmer, sometimes considerably warmer than now.
Actually, you have done nothing of the sort. You haven’t even identified the individual sources, much less shown you understand what areas of the planet they represent. Remember, the Vostok project is an austral locale and not a boreal locale as you tried to claim. Can you even give a correct identification for the source of your graph and each of its data sources? No handwaving, broad generalizations, or pile of bibliographic references. What is the specific source and authority for each claimed dataset? What sources opposed the conclusions of the paper and why?
Let me ask you guys a question. Why is Venus hotter than Mercury?
REPLY: Let me ask you a question, is Earth Venus?
Give it up – it’s getting old, this thread will close soon – Anthony
Dr. Everett V. Scott says:
“D. Patterson is correct when he states that there is evidence that the Earth was warmer overall at times during the Medieval Warm Period. Dr. Loehle used eighteen different (non-tree ring) proxies, all of them peer-reviewed, and all showing MWP temperatures as high or higher than present global temperatures. Please see the links in my previous post.
There is globally synchronous multi-proxy evidence showing unequivocally that prior warm periods were in fact warmer than today’s temperatures. The IPCC showed this in AR-1:
http://jonova.s3.amazonaws.com/guest/de/temps-ar1.jpg“
Both the Loehle paper and the graph linked above terminate in the early part of the 20th century. There has beed some 0.8°C of warming since then taking current temperatures above those shown for the MWP.
Dr. Everett V. Scott says:
“multi-proxy evidence from multiple ice cores in both hemispheres shows definitively that the earth has been warmer, sometimes considerably warmer than now.”
During the Holocene? Those were Smokey’s terms of reference. If so, post a link for these multi-proxy studies.