The Science is Settled: New Tree Ring Study Finds Roman Period Likely Warmer Than Today

Today appears to be global warming day here at Hit & Run. As some astute H&R commenters have noted, Nature Climate Change has just published a new study by German climate researchers that peers deep into the entrails (OK the heartwood) of Scandinavian trees to figure out how temperatures have trended since the 2nd century BC.

The abstract of the article, Orbital Forcing of Tree Ring Data, sums up:

Solar insolation changes, resulting from long-term oscillations of orbital configurations, are an important driver of Holocene climate. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750, but the trend varies considerably over time, space and with season. Using numerous high-latitude proxy records, slow orbital changes have recently been shownto gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (−0.31 °C per 1,000 years, ±0.03 °C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models, indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.

This graph summarizes their findings:

"This figure we calculated may not seem particularly significant," says [Jan] Esper [one of the researchers], "however, it is also not negligible when compared to global warming, which up to now has been less than 1°C. Our results suggest that the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia."

The folks over at RealClimate welcome the new results but suggest that other reconstructions of tree ring data outside of the northern latitudes will find that orbital forcing (sunlight hitting the surface) actually has a far smaller effect on the global temperature trend than that reported in the new study. University of Pennsylvania climatologist Michael Mann (the creator of the "hockey-stick" which did not find evidence for a significant Medieval Waming period) tells The New Scientist: "The implications of this study are vastly overstated by the authors."

Time will tell if that is so.

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  • John||

    "The implications of this study are vastly overstated by the authors."

    Color me surprised that Mann would think that.

  • Cytotoxic||

    Fucking New Scientist. I'm glad they were forced to acknowledge this but I'm unsurprised they went to Mann for the review.

  • Bee Tagger||

    Hey, he knows a thing or two about vastly overstating things.

  • Sudden||

    Michael Mann went on to say "These fucking Germans put the 'rat' in 'it doesn't fit the narrative'"

  • ||

    And then he created Miami Vice.

  • Shmenge||

    I think Thief is his best movie.

  • ||

    Thief is great, and Drive reminded me a lot of it. Or at least seemed to have some homage for it.

  • Paul.||

    Thief is great.

    Collateral was excellent. And Heat was highly underrated.

  • ||

    omg yes. i remember when ronin got all the positive press, and heat was largely glossed over.

    imo, heat is vastly superior.

    also, the cop stuff in heat, while clearly not a documentary is at least reasonable and not ridiculous as many such movies are. it's not a procedural, but it doesn't cause MEGO

  • Paul.||

    I've posited that cop stuff in nearly every movie is not documentary.

    Nearly every damned cop movie on the planet has the two hard-charging, devil-may-care plain-clothes entering the residence of the pathalogically dangerous felon without even alerting HQ. I've NEVER seen anyone shoot a dog in a cop drama... not even in CHiPS! And hungover detectives are allowed to smoke cigars in a murder scene while standing over the body, cracking wise, drinking coffee and eating a sandwich (which is the kind of cop I always wanted to be-- screw the patrol fairy thing).

  • ||

    well , yes. i was speaking informally, but there is a rather large difference from movie to movie.

    some movies are PRETTY accurate, and others are complete hogwash.

    kind of like with firearms. how many movies does a semi-auto lock back the slide when empty and then the guy pulls the trigger and it goes "click"?

    as an example, car chases aside, the french connection was better than most.

  • Paul.||

    kind of like with firearms. how many movies does a semi-auto lock back the slide when empty and then the guy pulls the trigger and it goes "click"?

    "click" repeatedly... with an auto... REPEATEDLY! God I hate that.

  • BarryD||

    If anyone knows from "vastly overstated by the authors", it's Michael Mann. He probably takes the prize, in all of science, for the whole of human history.

  • T||

    Pons and Fleischmann come to mind.

  • BarryD||

    How long did they continue to defend their paper after their results couldn't be reproduced?

  • Brett L||

    I once read a paper by a Chinese University group that purported to get 110% conversion on a chemical process. That one is still my personal prize.

  • fish||

    I bet the team gave 110% when writing the paper.

  • BarryD||

    So would you, if you wanted to avoid the flogging.

  • Killazontherun||

    To be fair, I slipped a little anti-matter in to skew the results, and they just reported what they saw. Quite a gag, eh?

  • Brett L||

    Not sure how that would affect cellulose conversion to sugars, but cool.

  • ||

    Color me surprised that Mann would think that.

    What is interesting is that many who did this study were or are on Team man made Climate change.

    The greatest implication of this study may not be that CO2 is not causing global climate change...it is that team man made climate change may have just thrown Mann under the bus.

  • Pro Libertate||

    How do you say AGW in Latin?

  • ||

    Hottus Maximus

  • ||

    I forgot to add that this is also Latin for "Allison Brie".

  • Brett L||

    Uh, should she be Hotta Maxima?

  • ||

    You are technically correct, which is the best kind of correct.

    Sorry I didn't genderize a joke. Jerk.

  • Brett L||

    I'm feeling very pretentious today. And pedantic. But not pedophilic. Never that.

  • ||

    It's odd that you felt it necessary to bring that up. Were you with Warty last night?

  • Brett L||

    Were you with Warty last night?

    **runs sobbing from the room**

  • Auric Demonocles||

    Yet you couldn't make that joke yesterday? Would you say you were "young and reckless"?

  • ||

    Severely-reduced pay all around!

  • Auric Demonocles||

    I'm sorry, but I have to leave. I have a regulation date.

  • DaveAnthony||

    That will end in regulation disappointment.

  • Fist of Etiquette||

    Redde Caesari quae sunt Caesaris

  • Sudden||

    De Bello Lemures

  • db||

    Just started The Last Days of Jericho the other day (not much time to read this week) and it is starting off very well.

  • robc||

    I prefer it to Lemures.

    Which surprised Fluffy.

  • Scotticus Finch||

    I really enjoyed Jericho. I thought it could have easily been 200 pages longer, which is rare these days, especially for self-publishing.

  • robc||

    It could have been much longer, but I think it was probably just about right.

  • Scotticus Finch||

    Since I wanted more when it was over, I'd say you're right.

    You hear that, Robert Jordan's corpse?

  • Jesus H. Christ||

    I was beaten to submission by the fourth volume. While browsing other fantasy fiction in a bookstore, I noticed the Jordan dreck and commented to my wife on what a tedious, repetitive, derivative and generally poorly written pile of pooh it was. The guy standing nearby was a Jordan fanbois, and took serious offense. I mean, it was as if I had insulted him personally.

  • Killazontherun||

    You did tell him he has taste for shit, but believe me, you did the right thing. Jordan fanbois, he needed to know.

  • Sudden||

    I just started Lemures last weekend, but haven't been able to get beyond the third chapter as a direct result of too much work and a MW3 diversion. But I'll be heading to Vegas this weekend and if I get cleaned out early, I'll spend the remainder of my time catching up on my reading.

  • Fatty Bolger||

    dolus malus

  • Drake||

    If only the Emperor had taxed carbon...

  • Cytotoxic||

    Did the authors discuss the geographical distribution of the Roman warm period? I believe there is at least some evidence that the warming occurred all over the world not just Europe.

  • Tulpa the White||

    Tree rings only develop in temperate regions, and many parts of the world do not have old forests to begin with (such as the oceans, obviously).

  • ||

    here is law dome ice cores

    http://climateaudit.files.word.....ompare.png

    and here is some Greenland ice cores

    http://westinstenv.org/wp-cont.....000yrs.jpg

  • Paul.||

    *squints*

    Do these graphs indicate as much global cooling as I think they do?

  • ||

    Regional cooling not global. (this is the mistake the alarmists make ever time they see warming in the US south or in Russia or Hurricane Katrina)

    Taken together with further evidence they could indicate global cooling over the long run.

    One thing is sure Greenland is not melting anytime soon.

  • ||

    Oh god, the spluttering from the cultists as they scramble to deny that this is science is going to be epically hilarious. Come on, morons!

  • Brett L||

    Of course Real Climate thinks the implications of this study are "vastly overstated". They are the very heart of the true believers. Its like proving Christ didn't exist and going to the Vatican for a quote.

  • db||

    That is a beautiful analogy.

  • JW||

    Huh. You'd think they'd welcome good news.

    "Good news everyone! We're not all going to die horrible deaths from climate change! In fact, things look like their cooling off!"

    "Yeah, right! Pull the other one now, you lying liar! (How the fuck are we going to raise more money off the corporate rubes wanting to look "green?")"

  • Paul.||

    That's not how it works. It's "Bad news, everyone! Our seat at the table where we get to dictate policy for billions of people is jeopardized! No one will listen to us!"

  • Tulpa the White||

    The finding does not change our understanding of the warming power of carbon dioxide. In fact, it shows that human CO2 emissions have interrupted a long cooling period that would ultimately have delivered the next ice age.

    Stupid humans screwing up the planet again.

    Mann argues that Esper's tree-ring measurements come from high latitudes and reflect only summer temperatures.

    I'm sure Dr. Mann has an explanation of how either of those characteristics could plausibly bias the results. We simply do not have, and cannot have, a randomly-selected temperature sample from thousands of years ago. We have to go by what's available and check for plausible sources of bias.

  • Bee Tagger||

    The finding does not change our understanding of the warming power of carbon dioxide. In fact, it shows that human CO2 emissions have interrupted a long cooling period that would ultimately have delivered the next ice age.

    They'll have their control over human behavior one way or another.

  • Auric Demonocles||

    In fact, it shows that human CO2 emissions have interrupted a long cooling period that would ultimately have delivered the next ice age.

    This shows two things:

    1) The global cooling craze was correct!

    2) We should be thanking the oil barons for saving us from hunting mammoths.

  • T||

    I'm totally down for smoking some mammoth ribs.

  • ||

    What kind of rub would you use on mammoth?

  • ||

    One from Elizabeth Warren's cook book that includes mayo, oats, onions, tomatoes and chicken broth.

  • mad libertarian guy||

    Sounds good, but only if you use Empire Mayo.

  • ||

    SFed the link.

  • tarran||

    I would take this paper with a huge grain of salt.

    When Dendroclimatologists claim to reconstruct temperature, it's the equivalent of a chiropractor manipulating your neck to diagnose you with cancer.

    Numerous factors affect tree growth. temperature is actually a minor one. The factors include wetness, CO2 levels, nutrients in the soil, bug infestations etc.

    Moreover, the thickness of the rings peak when an optimum is reached. So, if the ring gets thinner, is it because temperature fell? Or is it because the temp rose above the optimum? Or perhaps something ate half the leaves and the tree had stunted growth? Or maybe it was really cloudy and the tree got very little sun?

    About the only thing these studies will tell you is whether a bunch of trees had good years for growth or not.

  • Brett L||

    Thank you. Good point. I'm having fun watching Mann et al getting hoist on their own petard, but I truly believe there is no real conclusion to be drawn from tree-ring data w/r/t average global or regional temperatures.

    (Which may be important as England is having a cold wet summer while the US Midwest is hot and dry. Which tree rings should we believe?)

  • tarran||

    I'm having fun watching Mann et al getting hoist on their own petard

    I used to feel that way. The thing is Mann'sso bad at math that it's the equivalent of the hockey game between South Park pee-wee hockey team and the Detroit Red Wings. After a while you just don't want to watch anymore because it's just a merciless beat-down.

  • BarryD||

    The moment he doesn't appear in articles like this, is the moment I won't care about him being so hoisted. He deserves a metaphorical beat down, over and over, until he finally leaves the ring for good.

  • Killazontherun||

    Funniest show ever, no second funniest after the killer whale on *SPOILER ALERT* (though inevitable) the moon episode. *SPOILER ALERT* Just so brutally merciless, by the time the kindergarten kid says, 'I hate you coach' it is transformed into sublimely funny punchline due to the episode length set up.

  • Juice||

    No. The funniest SP episode is the Jennifer Lopez episode. The second funniest is when Butters is a pimp.

  • PapayaSF||

    The recent Reverse Cowgirl episode (about toilet seats and the TSA) was great.

  • Peter L||

    As one who does not watch South Park, More details please? What do they say about the TSA?

  • PapayaSF||

    You can watch it here. Description here.

  • Tulpa the White||

    The hockey stick graph is based on tree ring data too.

  • #||

    Tree ring data that is also fudged.

    But yes, tree ring data is very sketchy at best. It's not a reliable data source.

  • BarryD||

    It's a veritable tree ring circus.

  • OO=======D||

    Maybe you should leave.

  • ||

    HEY-OHHHHH!!!

  • Coeus||

    Yep, I can't wait for him to go all out and start writing about the exact same "uncertainties" his detractors do.

    Delicious.

  • Cytotoxic||

    Good points.

  • ||

    I would take this paper with a huge grain of salt.

    I know I am waiting until Steve McIntyre to weigh in....lets hope they give him the data unlike other studies tend to do.

    He has no problem tearing new assholes into papers that support skeptics if they are done badly.

  • tarran||

    The first sign to me that climatology was being dominated by pseudo-scientists was the way they treated McIntyre.

    All the guy cares about is reproducing the calculations in papers. Full Stop.

    If Mann et al had behaved with integrity, and fixed their mistakes instead of screaming "Oil Industry Shill" - they might have a case in their claim that AGW is significantly impacting the Earth's climate.

    The fallout of the bad science is that we don't know - although it's increasingly looking to me like CO2 is well back in line behind the Earth's Orbit, Solar Weather, Cosmic Ray Intensity, Volcanic activity.

  • Sam Grove||

    If Mann had behaved with integrity, it might not have improved his case, but it would have improved his credibility.

  • ||

    200 to 400 ppm. Do the math. Twice nothing is still nothing. The entire theory is horseshit without the feedback loops, which are extremely suspect.

  • Sam Grove||

    That's why you have to use lots of trees and not the relative few that were said to be evidence of impending doom.

  • Sudden||

    I would take this paper with a huge grain of salt.

    Don't tell Bloomberg or Michelle O. They will make you pay a stiff tax for that grain of salt.

  • Paul.||

    Grains of salt are bad for you.

  • db||

    This is my thinking as well. If Dendrowhosiwhatsis is shaky ground on which to found one hypothesis, it is for all hypotheses.

  • ||

    "About the only thing these studies will tell you is whether a bunch of trees had good years for growth or not."

    Thank you tarran, you are exactly right. I am also tired of watching the climate scammers 'beat down' in debates. Now I just want to see them beat down in earnest.

  • Johnimo||

    I believe the authors were meticulous in controlling for other variables by studying a control group of trees from an alternate location. While short term cooler temperatures in a locale do not indicate worldwide trends, over long periods of time such decreases are indeed indicative of wide trending.

  • SKR||

    Right, which is why this paper with 560ish series of data produces a more complete picture than the previous paper with 56 series of data.

  • Not an Economist||

    Supposedly they correct for all the other factors. Whether they are accurate or not I have no idea.

  • Cytotoxic||

    OT: what does Reason think of this study stating that longer prison sentences reduces crime? http://www.guardian.co.uk/law/.....sfeed=true

  • Bardas Phocas||

    The Romans preferred to curcify their criminals. They still got overrun by a bunch dirty germans.

  • Sudden||

    In all fairness, the Germans have historically managed to crush everyone outside of these United States.

  • ||

    The British and the Swiss disagree.

  • robc||

    Most of the swiss are germans.

    And for that matter, find a Briton. Most are Angles or Saxons or Jutes or Normans. In other words, a bunch of germans.

  • ||

    Pointing out that 'white' people are the most efficient killers in history make you a racist. Shame shame.

  • Coeus||

    Gotta have something. Dancing, basketball and high SAT scores are already taken.

  • ||

    The Romans repeatedly crushed the Germans for hundreds of years before that. Things change. Ocelot's ears and peacock's tongues go out of fashion as dinner delicacies. You know what I mean.

  • T||

    Ocelot's ears and peacock's tongues go out of fashion as dinner delicacies.

    Really? Shit, now I have to go call the caterer about Saturday night.

  • Virginian||

    Look at his little spots! Look at his tufted ears!

  • ||

    In all fairness, the Germans have historically managed to crush everyone outside of these United States.

    Mexico hasn't been crushed by Hansel....same with China.

  • Paul.||

    Mexico hasn't been crushed by Hansel....same with China.

    You know who was crushed by Gretel?

  • Drake||

    Mexico managed to become a French puppet state. The Germans couldn't be bothered.

  • Sam Grove||

    It seems obvious that if criminals are kept locked up longer, they would not be able to commit as many crimes outside of prison.

  • Zeb||

    I'm all for long prison sentences for crimes that actually should be crimes.

  • ant1sthenes||

    Common sense? If you put everyone in prison forever, there would be no more crime (outside of prison, that is, but who cares what happens to a bunch of filthy criminals in gaol?).

  • Romulus Augustus||

    Damn Romans releasing CO2. All that bread they baked and don't get me started on circuses as emitters.

  • ||

    But hey, their execution methods were green at least! No burning at the stake for them, just carbon-neutral crucifixion!

  • ||

    Oh, bullshit. Crucifixion allows the victims to continue exhaling CO2 for days. A truly enlightened civilization would stick to the truly green Blood Eagle.

  • ||

    Are you saying decimation wasn't green?

  • ||

    Killing a mere 10% of humans isn't going to save the world from climate change, you corporate stooge.

  • Pro Libertate||

    That's actually not true. The cedar planks used for crucifixion absorbed any CO2 exhaled by victims of righteous justice.

  • fish||

    The cedar planks used for crucifixion absorbed any CO2 exhaled by victims of righteous justice.

    Tell that to the poor cedar plank cooked Copper River salmon that I enjoy so much.

  • ||

    This study only looks at a small area.

    It is not the end all and be all.

    University of Pennsylvania climatologist Michael Mann (the creator of the "hockey-stick" which did not find evidence for a significant Medieval Waming period) tells The New Scientist: "The implications of this study are vastly overstated by the authors."

    What is amusing is that real climate says this study solves the "divergence problem".

    It does not have a divergence which is true but it does not solve Mann's problem with his hockeysticks.

    This study may not have a divergence but the decline that he hid using a trick is still in his 1998 study.

  • Juice||

    This study only looks at a small area.

    So did the all the hockey stick studies. They only looked at trees in a few places in Scandinavia and Russia.

  • ||

    So did the all the hockey stick studies.

    You will get no argument out of me. Those hockey stick studies are piles of crap. The fact that many of them rely one tree in Yamal to hold their thesis together is just one of many mistakes that can be found in them.

    We may have a good study here. Time will tell. Lets not make one of the many mistakes alarmists have made and claim one study is the holy grail.

  • Sam Grove||

    I'm wondering about the implications for Mann's reputation.

  • ||

    Leaving out the true believers, it really has nowhere to go but up.

  • fish||

    ...it really has nowhere to go but up.

    I'm an optimist! I think it can go lower still!

  • The Hammer||

    If he doesn't get punched in the face every time he goes out in public, it can still go lower.

  • Ken Shultz||

    Time will tell if that is so.

    I haven't even read any of the comments in this thread yet, but I'd bet dollars to tree rings that there are people in this thread who were ready to tell us the true implications of this study from the get go.

  • ||

    And you would win. tarran did it beautifully.

    "About the only thing these studies will tell you is whether a bunch of trees had good years for growth or not."

  • ||

    Solar insolation changes, resulting from long-term oscillations of orbital configurations, are an important driver of Holocene climate. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750

    I think them finding a signal of solar insoluation cycle may be complete bullshit.

    Without that straight line drawn on the graph you have long periods of warming and cooling. Without that last bit of cooling from say 700 to 1700 would there be a solar signal? Is the signal just an accident of timing? Certainly of you only looked at the first 700 years you would not see it...or if you only looked from 1000 to 2000 you would not see it. How is this any different then a bound random walk that happened to randomly walk downward near the end?

  • ||

    How is this any different then a bound random walk that happened to randomly walk downward near the end?

    Or high 2000 years ago. Unless they can explain the times when it cooled faster then the trend and when it warmed faster then the trend and isolate them from the signal I really do not see how they can make the claim that it is caused by the orbit....the fact that it is a .03 degree per 1000 years signal also seems hysterically impossible.

    What the fuck is the error bar? plus or minus 0.003?

    Give me a fucking break.

  • ant1sthenes||

    Part of me wonders whether this paper isn't just a ploy to get climate alarmists to start pointing out all the problems with tree ring data, so that they can have written confirmation from respected climate scientists that the tree data used in numerous alarmist papers is unreliable BS.

  • Russell Seitz ||

    After 2 hours and 12 minutes Mike Mann is still right, and likely to remain so because the paper in question has almost no bearing on radiative forcing.

    All that is at issue is the difference between the author's still small estimate - 0.3 degrees _per millennium_ of orbital climate forcing , and the slightly lower numbers in the 2007 IPCC report.

    What sort of Viking turns tail if the air turns 300 millidegrees colder?

  • Tulpa the White||

    What sort of Viking turns tail if the air turns 300 millidegrees colder?

    Climate isn't weather.

    We're supposed to be giving up fossil fuels over one degree in a century, remember?

  • Russell Seitz ||

    "Climate isn't weather"

    You've misread the paper in question if you've read it at all : The orbital forcing can only have changed the climate of Viking Greenland by 30 millidegrees per century

  • CPBrown||

    It was just the heat from Rome burning while Nero fiddled.

  • ||

    Hey Ron

    Mann is at Penn State, not Penn.

  • Epicdelusion||

    not find evidence for a significant Medieval Waming period)

    Warming*

  • TomB||

    Tarran is pretty much right. My master's thesis is on dendroclimatology, and you can get the chronologies to tell you whatever you want them to tell you.

    You can try it out yourself; dendro and meteorological data are available online. Calibrate a tree-ring chronology with the past 50 years of meteorological record, then reconstruct the previous 50 years, and compare the reconstruction to the actual meteorological records. You'll see how disturbingly unreliable this "science" is. Now extrapolate that out 1,000 or 2,000 years...or more. The reconstructions are as reliable as my uncle Phil.

    And don't get me started on the "divergence". That's just code for "We realize that dendroclimatology is bogus, but we'll try to distract everyone else from that fact with the most transparent and hypocritical excuse ever concocted."

    By the way, of the dendro folks I know, about 80% of them acknowledge everything I just said (at least behind closed doors...they of course sell the shit for research grants...which is the counterpart of "big oil" only with less accountability).

  • PapayaSF||

    Are they in the pay of Big Tree?

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