Since Princeton’s Dr. Michael Oppenheimer conflated weather with climate last week, proclaiming a short lived heat wave as “This is what global warming really looks like” in a media interview, it seems only fair to show what real science rather than what he and Dr. Trenberth’s government funded advocacy looks like. I can’t wait to see how Dr. Michael Mann tries to poo-poo this one. – Anthony
From Johannes Gutenberg-Universität Mainz: Climate in northern Europe reconstructed for the past 2,000 years: Cooling trend calculated precisely for the first time
Calculations prepared by Mainz scientists will also influence the way current climate change is perceived / Publication of results in Nature Climate Change
An international team including scientists from Johannes Gutenberg University Mainz (JGU) has published a reconstruction of the climate in northern Europe over the last 2,000 years based on the information provided by tree-rings. Professor Dr. Jan Esper’s group at the Institute of Geography at JGU used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC. In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
“We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low,” says Esper. “Such findings are also significant with regard to climate policy, as they will influence the way today’s climate changes are seen in context of historical warm periods.”
The new study has been published in the journal Nature Climate Change.Was the climate during Roman and Medieval times warmer than today? And why are these earlier warm periods important when assessing the global climate changes we are experiencing today? The discipline of paleoclimatology attempts to answer such questions. Scientists analyze indirect evidence of climate variability, such as ice cores and ocean sediments, and so reconstruct the climate of the past. The annual growth rings in trees are the most important witnesses over the past 1,000 to 2,000 years as they indicate how warm and cool past climate conditions were.
Researchers from Germany, Finland, Scotland, and Switzerland examined tree-ring density profiles in trees from Finnish Lapland. In this cold environment, trees often collapse into one of the numerous lakes, where they remain well preserved for thousands of years.The international research team used these density measurements from sub-fossil pine trees in northern Scandinavia to create a sequence reaching back to 138 BC. The density measurements correlate closely with the summer temperatures in this area on the edge of the Nordic taiga.
The researchers were thus able to create a temperature reconstruction of unprecedented quality. The reconstruction provides a high-resolution representation of temperature patterns in the Roman and Medieval Warm periods, but also shows the cold phases that occurred during the Migration Period and the later Little Ice Age.In addition to the cold and warm phases, the new climate curve also exhibits a phenomenon that was not expected in this form.
For the first time, researchers have now been able to use the data derived from tree-rings to precisely calculate a much longer-term cooling trend that has been playing out over the past 2,000 years.
Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium due to gradual changes to the position of the sun and an increase in the distance between the Earth and the sun.”This figure we calculated may not seem particularly significant,” says Esper. “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.”
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Orbital forcing of tree-ring data
Jan Esper, David C. Frank, Mauri Timonen, Eduardo Zorita, Rob J. S. Wilson, Jürg Luterbacher, Steffen Holzkämper, Nils Fischer, Sebastian Wagner, Daniel Nievergelt, Anne Verstege & Ulf Büntgen
- Received 27 March 2012 Accepted 15 May 2012 Published online 08 July 2012
Solar insolation changes, resulting from long-term oscillations of orbital configurations1, are an important driver of Holocene climate2, 3. 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 (ref. 4), but the trend varies considerably over time, space and with season5. Using numerous high-latitude proxy records, slow orbital changes have recently been shown6 to 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 models7, 8 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 reconstructions9, 10, 11, 12, 13 relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.
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I’m sure Steve McIntyre will give this paper a thorough examination for the same sorts of issues we’ve seen before in MBH98. Hopefully he won’t have to beg for years to get the data for replication like he did with Mann.
h/t to WUWT readers “Typhoon” and Dr. Leif Svalgaard
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Either we believe in treemometers or we don’t. It seems to me a bit hypocritical to rage against them when they support the warmist hypothesis and for them when they don’t!
Surely history has relevance and why it tends to be pushed aside by the “consensus” speaks volumes about academic historians today who seem to sit idly by while their climate academic colleagues run amok over the same period that is rightfully theirs. How can climate alarm believers toss the following aside:
1) Knowing that Medieval Scotland’s wines were much enjoyed in Europe at the time.
2) Knowing that the present warm period has only begun to uncover Viking farmsteads in Greenland – we need maybe another degree or so over the next 50 to 100yrs to permit archeologists to properly examine the settlements.
3) Knowing that New York Harbor, the Thames and the Bosphorus froze over during the LIA and Swiss villages of hundreds of years old in the valleys were crushed under advancing glaciers.
4) Rome’s most feared enemy, Hannibal Barca of Carthage in about 200BC, circled around through Spain, over the Pyrennes, up the Rhone River in Switzerland and over the alps with his elephants to surprise the Romans. I skiied in the Canton Vaud overlooking the Rhone in the early 1960s – no elephant could have negotiated the crossing under present conditions.
5) Oezti, the neolithic European, mummified under mountain ice in the Alps, finally thawed out in 1991 on a mountain pass where he died of wounds, with his weapons and belongings neatly laid beside a rock, after being ice bound for over 5000 years. This isn’t a bad proxy for a warm period approximately like now over 5000 years ago.
Can we inveigle a timorous historian to come forth and write a historical-based chronicle of the earth’s climate over the past 10,000 years or so. It would be understandable to the layman and would be entertaining to see how the hottest-period- of-the-last-millennium cheering section would handle it. It would have enhanced the current U of Mainz paper had it included such.
Gail Combs: “If you bothered to read all the comments you will see most of us are STILL saying tree rings are bad proxies.”
This isn’t pointed at you, but there’s a depressing lack of awareness about what ‘evidence’ is, what it signifies, and its use in discussion and thought. Especially as to the general idea of displaying or highlighting incoherence and inconsistency. It’s about impossible for me to produce evidence of why your position is incoherent. But if you produce evidence that your position is incoherent then the best thing I can do is put that up in marquee lights until awareness of your own position is hammered into your own skull.
*If* you accept that Global Warming is occurring and/or unprecedented. *And* you accept that treemometers are good proxies. *And* you accept that peer review prevents errors then:
The science shows that we will burst into flames at the same time that we are buried under glaciers.
Give up whichever position you prefer, but you cannot hold all of them. Tim Ball modified hangout of seasonally selective global warming is an interesting notion. But then if we accept that summers are getting colder and that winters are getting warmer it is not Global Warming, but advancing toward a Climatic Equilibrium. But if that’s the case then we cannot claim that CO2 is the responsible party unless we claim that CO2 does not play catch and release with photons. But that it saves summer photons as currency to pay for lift passes when the powder is fresh on the ski slopes.
Dan Marsh says:
July 10, 2012 at 10:44 am
“The Earth is cooling 0.3 degrees C per millennium, because … increases in the distance between the Earth and the sun. WAIT, WHAT?!!!
Since when is the earth rapidly flying away from the Sun? I mean if distance to the sun is even a 1% factor in that, within a few million years, life on Earth would be doomed!”
Orbits vary due to interaction with other planets’ orbits in the solar system. Earth Sun distances vary but do not simply increase or decrease in a linear fashion. The Earth’s orbital shape vassilates over time causing the Earth Sun distance to change to closer at times and farther at other times. See the Milankovich cylcles for more on this.
My layman’s take away on this is that tree are still a poor proxy for past temperature but these guys were more thorough and honest with their work and research than Mann “et al” have been. It contradicts what the tree-ring channeler concluded. So now what is he going to say?
(PS I didn’t have time to read all the comments so I may be repeating what someone else has already said.)
Gail
Very interesting. One of the ways that farmers survived during the lia is that they had mixed farms so if one crop failed another grew. The trouble today is that modern farming and economics are based around single crops. Hence the need for a plan b
Tonyb
This paper is big because not only does it confirm skeptic arguments about the MWP/RWP, but it also confirms low climate sensitivity.
In the paper, they state that the orbital forcing over the last 2000 years was 6 w/m^2, which gave a temperature response of around -0.6 Degrees C.
This would give you a sensitivity of around 10 w/m^2/K which would represent very low climate sensitivity.
This would mean that the total net anthropogenic contribution to the warming observed of 0.8 Kelvin would be only 0.15 K, which would be around 18-19% for the contribution of the anthropogenic forcing to Global Warming.
“Medieval Scotland’s wines were much enjoyed in Europe” – who says? Let’s not over-egg the cake.
Now you know why Mann chose to go back only 1000 years. If he went back any further. his scam would be exposed.
This is why Gore only goes back to 1958 to see CO2 rising. If he went back 6E8 years like Berner, you would see CO2 18 times higher than today.
If you look at Scotese’s Paleotemp you would see today’s temperature is only 25% off the bottom of a normal range for the last 5E8 years.
@Gail.
gees Gail, I live in a city, ain’t no horses here..
Just saying that in medieval and roman times.. there were lots of horses, knights in armour, roman legions with chariots etc and there seems to be a definite correlation.. dark ages was cold, and all the horse got et…. and now you tell me that there are STILL lots of horses.. and we are in another warm period.. so there …. further proof of my hypothesis. :-))
at least as solid as the CO2 hypothesis, anyway.
Dan Marsh says:
July 10, 2012 at 10:44 am
The Earth is cooling 0.3 degrees C per millennium, because … increases in the distance between the Earth and the sun. WAIT, WHAT?!!!
Since when is the earth rapidly flying away from the Sun? I mean if distance to the sun is even a 1% factor in that, within a few million years, life on Earth would be doomed!
_______________________________
This tutorial on the Milancovitch cycles gives an excellent visual of what is meant in that comment. He is talking about Eccentricity.
From Lubos Motl excellent site, an article by Gerald RoeIn Defense of Milankovitch
http://www.gov/projects/ A quick background to the last ice age
Another graphic explanation
http://deschutes.gso.uri.edu/~rutherfo/milankovitch.html
And just for the added info.
Ice ages Confirmed
Sun’s movement around galaxy
Galaxy’s Spiral Arms, Ice-Age Epochs and the Cosmic Ray Connection By Nir J. Shaviv
Lesson from the past: Present Insolation Minimum Holds Potential for Glacial Inception 31 July 2006
Temperature and precipitation history of the Arctic:… Solar energy reached a summer maximum (9% higher than at present) w11 ka ago…
http://wattsupwiththat.com/2010/10/30/new-peer-reviewed-paper-says-there-appear-to-have-been-periods-of-ice-free-summers-in-the-central-arctic-ocean/
Hey, I’ve realised that Mike Mann must have used cherry trees for his proxies. What do all of you think?
“but these guys were more thorough and honest with their work and research than Mann “et al” have been”
No, not possible
Mann is the epitomy of honesty and transparency, and highly knowedgable on stats / biology etc etc ..
/sarc !!!
Yah know Gail ….
Fer a dumb hick farmer from them there upstate Piedmont hills ‘n hollars of rural Podunk Appalachia, you shore do have good research abilities …. 8<)
Kelvin Vaughan says:
I was just watching an old 1990 episode of Agatha Christie’s Poirot the detective and he said to his sidekick Hastings, “Did you know the world is cooling 3 degres every 12,000 years.
Again, this perposterous implication of linearity. ;-))
Will says:
July 10, 2012 at 11:40 am
……. The issue is does adding CO2 above and beyond naturual causes increase the rate of warming beyond what we can safely adopt to.
________________________________
No Will, you are missing the really big picture and therefore the actual issues.
#1. CO2 levels were actually getting dangerously low for continued plant life. So low plants had evolved the C$ and CAM mechanisms to cope with the starvation level CO2 during periods of glaciation when CO2 is absorbed by the colder water and the level falls dramatically.
Here is a peer reviewed paper on the subject:
Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California
#2. If CO2 causes some warming, ~ a climate sensitity to CO2 (doubling) of 0.3C is one calculation without adding in the amplification that is not a proven fact – then given we are at the END of this interglacial and the temperature is headed DOWN due to the increase in the distance of the earth from the sun, the more CO2 the better!
GRAPH: five interglacials and CO2 Present is on the right and the CO2 although higher is NOT causing a major increase in the temperature. As shown on this graph the temperature is gradually falling throughout the Holocene interglacial and we are at the bitter end.
Again a couple of peer reviewed papers:
There is a bunch more discussion on the subject here: The End Holocene, or How to Make Out Like a ‘Madoff’ Climate Change Insurer
At this point I much rather chance higher temperatures than a return to Little Ice Age conditions or worse.
Comparing contemporary temperature records with tree ring proxy data is mixing apples and oranges. They are measuring two different things. Thermometer temp records are year round, where as tree ring data omits winter because the trees are dormant. Thus, as noted in the abstract, this is changes only of summer growing conditions (including a rainfall component) and fundementally cannot be knitted with thermometer data averaged for the year. This was a major mistake of The Team as well.
Will says:
July 10, 2012 at 11:40 am
……. The issue is does adding CO2 above and beyond naturual causes increase the rate of warming beyond what we can safely adopt to.
If you consider where the CO2 is most likely coming from, its from coal that WAS ONCE TREES.
It got buried, lots of it, which greatly depleted the NATURAL level of CO2 in the atmosphere.
If you know anything about predetor/prey or food scarity algorithms, then it is pretty obvious that for many thousands of years the level of CO2 has been BARELY AT PLANT SUSTAINABLITY levels. (this is further confirmed when you consider that plants, and animals can survive, and indeed flourish, in CO2 levels many multiples of what we currently have.)
Finally, we are releasing some of this long lost carbon, and restoring the proper balance !!!
Well, as to be expected, over at Realclimate they are already ridiculing the “denier” response to this study and saying we are ignoring the rise in temps. since 1900.
This is an impressive study and it corroborates previous observations of a slow cooling Arctic. Thus Kaufman et al. (Science, 4 September 2009) published an Arctic temperature curve based on lake sediments that showed a two thousand year, linear, slow cooling that was followed by sudden warming at the start of the twentieth century. They attributed the cooling to a steady, orbitally-driven reduction in summer insolation. Spielhagen et al. (Science, 28 January 2011) likewise observed a similar slow cooling followed by sudden warming at the beginning of the twentieth century. Their data were obtained from a foraminiferal core taken from the Arctic Ocean near Svalbard. Combine this with the current study from the Johannes Gutenberg Universität and we have multiple independent confirmations of a two thousand year cooling trend. As to the warming that began in the Arctic with the twentieth century, I have determined that its cause was warm water carried north by by Atlantic Ocean currents and not any greenhouse effect. For the full story of Arctic warming, download this article:
http://curryja.files.wordpress.com/2011/12/arno-arrak.pdf
I suspect this is a far more rigorous methodology than the half baked Michael Mann approach with data he either did not know how to work with or data he manipulated and then hid the methodology bias. I’ll withhold final judgement though for the real experts to be validated and cross corroboration to shine through. That process will further isolate the hiders and weak model methods even if the concealment continues.
In order to really understand the meaningfulness and validity of this study you have to understand the very specific arctic conditions of the Finnish Lapland. Temprature is and has always been the limiting growth factor for this location. This fact vastly increases the scientific credibility of the results.
A Finn who knows Lapland
“Or a hockey stick with the hook broken off?”
Well, to be fair, it’s actually a blade, which has mathematically less severe consequences (thinking hyperbola vs. parabola). An extrapolated hook could have us all dead generations ago.
In all seriousness, I don’t hold much stock in tree rings (also not my field), but touché.
Erkki Saarikoski says:
July 10, 2012 at 8:17 pm
In order to really understand the meaningfulness and validity of this study you have to understand the very specific arctic conditions of the Finnish Lapland. Temprature is and has always been the limiting growth factor for this location. This fact vastly increases the scientific credibility of the results.
A Finn who knows Lapland
_______________________________________
Thank you,
The nice thing about WUWT is the number of experts who can increase your knowledge if you have an open mind.
I still want to see a critical analysis by some one like Steve M. and others. The amount of game playing with tree rings has left a nasty taste in the mouth of most of us.
So if the Romans declined in power because of change in temperature why didn’t the rest of the population of the world, i.e., outside of Rome, decline with the temperature in the same proportion—-meaning the Romans would have held the same level of power anyway?
Maybe it was something else?