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
Posted on 07/10/2012 12:53:24 PM PDT by Ernest_at_the_Beach
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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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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
But I have a question. Is that wood a tone wood?
fyi
Consider becoming a monthly donor.
It's easy, and with enough participants
we could eliminate FReepathons.
It has a shivering tone to it!
Ah, an overall cooling trend.
The cricket chirping from the MSM science illiterates is commencing.....
Welcome to Earth.
The only place in the Universe where the inhabitants complain if the temperature changes more than 1 or 2 degrees Celsius.
And we wonder why the aliens won’t talk to us when they visit.
So there HAS been climate change.......[/sarc]
LOL!
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tornadomark says:
How many want to bet that the Warmists will now declare tree rings unreliable?
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milodonharlani says:
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.
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R Taylor says:
The authors had the decency not to note that CO2 has done nothing but increase during this 2000 years of cooling.
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otsar says:
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.
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AndyG55 says:
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?
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ntesdorf says:
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.
It is so easy for the Lie-berals to lie to their moronic followers to simply pick any negative excursion on that graph and compare it to today and shazzzzam the temperature is rising.
To lie with statistics only requires the appropriate beginning and end point. Using SEGMENTS of that graph I can make a case for warming or cooling. Only when viewed over a long period of time (as was the goal of the original post) can a truthful picture of climate change be shown albeit no reason for the change can be extracted.
Unfortunately outside of FOX which the mouth breathers do not watch, the alphabet networks continue to push the glo-bull warming hoax.
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Rob L says:
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.
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Tim Ball says:
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
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ALERT
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Marks says:
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
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George says:
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.
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