This is what global cooling really looks like – new tree ring study shows 2000 years of cooling – previous studies underestimated temperatures of Roman and Medieval Warm Periods

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

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. – Click to enlarge

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
Nature Climate Change (2012) doi:10.1038/nclimate1589
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.

a, The reconstruction extends back to 138 BC highlighting extreme cool and warm summers (blue curve), cool and warm periods on decadal to centennial scales (black curve, 100-year spline filter) and a long-term cooling trend (dashed red curve; linear regression fit to the reconstruction over the 138 BC–AD 1900 period). Estimation of uncertainty of the reconstruction (grey area) integrates the validation standard error (±2 × root mean square error) and bootstrap confidence estimates. b, Regression of the MXD chronology (blue curve) against JJA temperatures (red curve) over the 1876–2006 common period. Correlations between MXD and instrumental data are 0.77 (full period), 0.78 (1876–1941 period), and 0.75 (1942–2006 period).

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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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Don’t worry about the decline. Once NASA GISS changes that algorithm to its v3.1 version, cooling will become warming!

Sean Peake

How did that ever get out of peer review?

Rob

Holy Roman Empire! This is big.

How many want to bet that the Warmists will now declare tree rings unreliable?

milodonharlani

Since the Holocene Climatic Optimum was even warmer than the Roman & Medieval Periods, the cooling trend would be yet more pronounced if extended back another 3000 years or more. Modern warmth is not exceptional, having been exceeded in at least two periods during the past 2000 years.
Perhaps even more tellingly, the previous Eemian Interglacial (114 to 130 kya), was much warmer than today’s Holocene Interglacial. As most here must know, Scandinavia was then an island, hippos swam in the Thames at the site of London, & the raised beaches of Alaska & fossil reefs of the Bahamas were formed. The interglacial before the Eemian (Hoxnian in the UK, Holstein in N. Europe & Mindel-Riss in the Alps, corresponding to Marine Isotope Stage 11, from 374 to 424 kya) was also warmer than our present Holocene. All this without benefit of a Neanderthal or Homo heidelbergensis industrial age burning copious quantities of coal, or even wood, & with “pre-industrial” CO2 levels.

Regional! Regional! Regional!!! Just like the Medieval Warming Period!! (sarc.)

The authors had the decency not to note that CO2 has done nothing but increase during this 2000 years of cooling.

Billy Liar

No wonder the Team like trees; you can get them to reveal anything you want about past climate.
Why not just accept that they are unreliable indicators of past climate?

milodonharlani

Is that a broom handle or a mop, with bulges in a couple of places? Or a hockey stick with the hook broken off?

Coalsoffire

Divergence problem solved!

timg56

Just curious, but if people have doubts about the quality of tree rings as temperature gauges, is there any reason to accept this with open arms?
I’d be interested in a discussion of the quality of data, methods and processes. It is from evaluating this among various studies that we might get a decent idea of how good tree ring data is and who is coming up with the most accurate interpretation of the data.

AnonyMoose

Release the hounds scientists!

Did they forget the “hockey schtick” post processor?

Jim G

Looks like Dr. Iben Browning was right, however, possibly for the wrong reasons, and in a much more gradual manner than he was predicting. But he was predicting global cooling. Looks like it has been going on for some time. Wonder when we can expect the glaciers to return to the midwest?

BarryW

Can’t be right. It actually shows the Roman and Medieval Warm periods. 😉
Of course Mannian science says that those are only local phenomena.

jcbmack

This coincides with what Bob Carter has been saying for years.

otsar

The cynic in me says that that we will see more publications like this pass peer review as policy makers try to extricate themselves from the corner they have painted themselves into. When I read temperature reconstructions, tree rings, and precisely calculate in the same article my scepticism goes up. I hope they make all of their reasoning and work available. Having said that, I hope this is good work and that there is more forthcoming.

What a relief: Some climate scientists are returning to science. Perhaps to avoid issues later, but they are doing the right thing. I hope others will follow.
Yes, a big step, wonderful.
K.R. Frank

If I’m skeptical about tree ring data showing no trend prior to 1900, why should I accept a study that shows cooling using diffrent tree ring data?
What sort of “density” are they refering to? Acutal wood density? or Rings per cm?
How good is the correlation with density to “summer” temperatures?
Do winter temperatures matter in debate about cooling or warming trends over 2000 years?
Were the individual tree-ring source proxies equally weighted (unbiased), or weighted by training on a hypothetical target?
My gut is giveing me red flags over the concept that this paper has too much in it. It simultaneously puts forth a Lapland dendochron-thermal reconstruction with an orbital cooling configuration and solar insolation changes. Each of these would warrent its own paper.
Interesting paper, but my skepticism works both ways.

Neville

Just a few questions. Does this only apply to the NH? Are there SH studies that show a similar result? The LIA seems to be earlier or pre 1500 at coldest period. Is the MWP a bit earlier? Seems to start 700AD and finish about 1200AD. Dark age cooling seems very pronounced.

ExWarmist

“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.”
So Trees are Thermometers after all?
Whether you have a warming narrative, or a cooling narrative, it’s still only proxy data. Frankly I don’t trust any tree ring results now.

RE: otsar 3:41 pm:The cynic in me says that that we will see more publications like this pass peer review ….
The cynic in me agrees we’ll see more cooling papers pass peer review now that the door for AR5 has closed.

AndyG55

Doesn’t ice core data show a gradual cooling over the whole Holocene? like this.
How well doe sthis match up against other reconstructions of the same period?

This looks uncannily like real Scientific Work for a change. Some climate scientists seem to have recalled that they are supposed to be doing rigorous science. Perhaps others will have the courage to follow them now.

Joachim Seifert

Anthony, give credit to whom it belongs: The number of – 0.3 C
downslope cooling per each millenium was already provided some
months ago by DONALD ARCHIBALD, in Figure 5,
Due 3 Temp Record 22 years smoothed, in your WUWT post “Ap
Index, Neutrons and Climate”…..
These above Mainz guys just repeat Donald and conclude their study with “this all
SUGGESTS that the IPCC MAY UNDERESTIMATE…..” ??
…..If someone cheats on my return change, should I day the next time:
Excuse cashier, I suggest that you may underestimate my due change??
JS
[REPLY: Uhh, did you mean David Archibald? -REP]

Green Sand

Stephen Rasey says:
July 9, 2012 at 3:53 pm
…….now that the door for AR5 has closed.

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Not quite there yet:-
“Cut-Off Dates for literature to be considered for AR5”
http://www.ipcc.ch/pdf/ar5/ar5-cut-off-dates.pdf
There will be lots going on that are not yet in the public domain.

Rob L

Too bad that it is treemometers, they will always have questionable validity.
That said as with ice-cores we see the 1000 year warming-cooling cycle that produced the Minoan, Roman, Medieval and now Modern warming, on this graph it appears to have an amplitude of about 0.5-0.7 deg (1-1.5 deg C peak to trough from linear trend). That this cycle coincides with modern warming (which started before significant CO2 rise) is very powerful evidence against “strong” CAGW. Gisp2 cores have similar amplitude, though the long term cooling trend is steeper at about 0.7deg/millenium.
Would be nice to see an expanded vertical axis and a few grid lines to get a better view of the temperature variation, that graph they produced is near useless without a vertical reference.

“This is what global cooling really looks like”?
No wonder I haven’t had to turn on the A/C–or a fan, for that matter–so far this summer.

Ally E.

Excellent! I bet they used more than one tree. 🙂

Apart from the fact that trees rings don’t, for the most part, reflect temperature, this study is even more problematic because it only looks at summer temperatures. All the actual records show that it is winter temperatures that change the most.
For example, summer temperatures were about the same at the nadir of the Little Ice Age around 1680, but winters were much colder, Since then summer temperatures have remained about the same and winter temperatures have increased creating an increase in annual average.
Summary; Trees don’t represent temperature and half a year doesn’t represent an annual record.
There have been similar studies of petrified trees from millions of years ago. As I recall all they showed was a distinct solar cycle. But that is not surprising because that was the original reasonable application of tree ring studies by Douglass.
A. E. Douglass was an astronomer whose main interest was dendroclimatology, particularly the relationship between midlatitude precipitation patterns, especially drought cycles.
http://ltrr.arizona.edu/sites/ltrr.arizona.edu/files/bibliodocs/Douglass, AE_Evidence of Climatic Effects in the Annual Rings of Trees_1920.pdf
I used his work because I found a similar 22 year drought cycle in a spectral analysis of approximately 200 years of precipitation data for York Factory on Hudson Bay that appeared correlated with sunspot activity. It was an alien idea even then (1982) as my doctoral committee initially rejected that portion of the work. I risked failure but insisted on its inclusion, which, to their credit, they approved.
Theodor Landscheidt later developed the relationship between solar activity and midlatitude droughts.
http://www.john-daly.com/solar/US-drought.htm

Richard M

This could be used to explain why the temperatures have not been rising. They just need a slight addition to the models to handle this new information. Of course, continued CO2 emissions will swamp this forcing and we will still all burn to death. It will just a couple of years later.

Neville

Is there any graph that shows the holocene temp both from Antarctica and Greenland ice cores?( together)
If so is the graph reliable and drawn in both cases from the data? I’ve never seen a reliable comparison on the same page that covers the last 11,000+ years.

I believe there have been other subfossil trees and stumps located in the Dead Sea region that show cooling started about 4000 to 5000 years ago. There was a great reduction in the level of the Dead Sea and a significant climate regime change when the Levant region assumed its current dry regime. Prior to that it was much wetter and the Dead Sea surface level was much higher than it is now. I believe it was this paper that I am thinking about from A. Frumkin (Quaternary Research, 2009)
http://geography.huji.ac.il/personal/Frumkin/pdf/QR%20Sedom%20wood%202009%5B1%5D.pdf

Esper the Non-Archiver… Timonen… Zorita… Luterbacher… all well-known names from Climate Audit and elsewhere. But this time the Medieval Warm Period is returned where it belongs, and the Roman Warm Period is there too. And overall there is temperature loss. What amazing news.

Luther Wu

Yeah, but what about the really top notch researchers at really top notch universities like Penn State and UVa and East Anglia and…
What? Coverups? Their reputations are tarnished? Oh, well… never mind.

Greg House

Abstract:
…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 …high-latitude proxy records…data from northern Scandinavia…cooling trend…signature… tree-ring proxy records… in line with coupled general circulation models…substantial summer cooling over the past two millennia…missing orbital signature…near-surface air-temperature reconstructions… relying on tree-ring data…
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I don’t know… proxies-schmucksies again.. and of course anthropogenic “forcing” is not absent… That’s the climate science “methods” as we know it… shouldn’t we be over it by now?

Occasionally you’ll see Warmistas talk about how they wish they could be found wrong so they can breathe a sigh of relief about humankind’s dire prospects. Well, this would be a good time for them to celebrate, in my humble opinion.

Tree rings do not, for the most part, represent temperature. Worse, this study only looks at summer temperatures when all the records show changes are almost always in winter temperatures.
For example, summer temperatures are essentially the same as they were at the nadir of the Little Ice Age in 1680 AD. SInce then the warming has been mostly in winter temperatures.
Summary; Tree rings don’t represent temperature and summer doesn’t represent an annual average.
A few years ago studies of petrified forest wood millions of years old showed a solar cycle. This is not surprising since that was the main objective of dendroclimate studies in the first place – the relationship between sun, precipitation and tree growth.
A. E. Douglass was an astronomer whose main interest was dendroclimatology, particularly the relationship between midlatitude precipitation patterns, especially drought cycles.
http://ltrr.arizona.edu/sites/ltrr.arizona.edu/files/bibliodocs/Douglass, AE_Evidence of Climatic Effects in the Annual Rings of Trees_1920.pdf
I used his work because I found a similar 22 year drought cycle in a spectral analysis of approximately 200 years of precipitation data for York Factory on Hudson Bay that appeared correlated with sunspot activity. It was an alien idea even then (1982) as my doctoral committee initially rejected that portion of the work. I risked failure but insisted on its inclusion, which, to their credit, they approved.
Theodor Landscheidt later also developed the relationship between solar activity and midlatitude droughts.
http://www.john-daly.com/solar/US-drought.htm

Robert of Ottawa

Fun to see the tables turned on Mann & Co, but I don’t by the tree-ring thing.

Marks

Appears Real Climate and Michael Mann began their spin a day ago on this story:
http://www.realclimate.org/index.php/archives/2012/07/tree-rings-and-climate-some-recent-developments/#more-12427

KnR

To be consistent if we claim trees are rubbish at recording temperature we have to accept that is the case when the results don’t support ‘the cause ‘ leave the picking of cherries to those who regard ‘useful data’ to be worth more than ‘valid data ‘.

I am curious why they felt obliged to add the “instrumental” data. Which “instrumental” data? Global? NH? Finnish Lapland?
It just seems an odd thing to add a set of thermometers to a set of treerings.

Does anyone know the background of these researchers — what they’ve previously published? Will CAGW proponents be able to dismiss this as more ravings of known skeptics?

I’ve no more confidence in these tree rings than I have in any other tree rings.
Remember, the problem with the hockey stick, is not the up-swing at the end. That is an inevitable consequence of picking tree-rings which match the apparent 20th century rise. The problem, is the lack of variation in the handle. Likewise, this series “smells” like noise.
I’ve got to the stage where I think all tree-rings tell us is how much people want to believe in climate proxies.

Babsy

Bob Tisdale says:
July 9, 2012 at 4:14 pm
Hey, Bob! I thrilled beyond description it hasn’t been 120 so far this summer in North Texas. It’s raining today and *COOL* LOL!!

While tree rings by themselves may not represent temperature, the combination of tree rings and the isotopes contained in the wood together can be a pretty good indication.

kim

We are cooling, folks; for how long even kim doesn’t know.
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kim

Go, Baby Warming, Go.
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leftinbrooklyn

Whether this data is accurate or not, or whether the warmist’s data is accurate or not, doesn’t even seem to matter anymore at this point, IMO. With so much ‘evidence’ pro & con, I think the only obvious answer can be: there is no change, man-made or otherwise, in the degree, in variations in speed, or in ways that the climate’s been changing since there’s been a climate.
We’ve just developed some really nifty technology to measure all these ‘changes’, which aren’t really ‘changes’ at all…

George E. Smith;

Dang ! I’ll have to check my 45,000 year old Kauri picture frame, and see what Temperature it was growing at.
Speaking of Temperature proxies; anyone know what is the Temperature at which asphalt melts so that aeroplanes can get stuck to the tarmac. Why the hell, didn’t somebody measure the runway Temperature, when that plane got stuck to the ground, in molten asphalt. I used to figure my upper air Temperature of +60 deg C went along with maybe as much as +90 deg C ground, but now I may have to revise my ground Temperature extreme to a higher value. That has all kinds of connotations re the cooling benefits of UHIs, with a bigger Wien shift, and higher surface gray body Temperature, radiating faster.