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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To be fair, we are only talking about Finland here. We need more evidence in other areas before we can draw too many conclusions.
The hockey schtick seems explainable by simply screwing up basic statistics by cherry picking, perhaps intentionally. Take the batch of data sequences and select those that meet a criteria of following the temperature record (rising – or worse – just changing) over the most recent times. Even worse, make that criteria the anticipated global average rise rather than the actual temperature records at the locations of the various tree sites. Doing this makes sure that unless the actual site temperatures followed this anticipated gobal average rise, the selected data sequences would not be following a real temperature that they had been subject to. This becomes a recipe for selecting series that randomizes the collection of data sets and strips out any real signal that might actually exist in te overall collection. When averaged together, one gets the hockey stick because only those data series that meet the criteria of changing in modern times (and we already know that a decline automatically gets the data set inverted) so it’s a done deal that there is a hockey stick blade. If one actually selects and filters out all of the data sets according to this criteria and destroys the temperature signal that might have existed in the whole collection, one is left with random noise – which averages out to zero – giving us the beautifully straight handle – simply providing us with no information that might have been present in the original data.
Also, by picking subsets of the collection, one then is violating the assumptions of statistics about the nature of the collection and the statistical processing and information is no longer valid. For instance, trying to evaluate a manufactured device by dividing the sample products used in a preliminary test into three groupings according to results and running different sets of tests on each and then trying to get statistical information about the overall manufacturing process based upon the original sample.
Just because mickie mann succeeded in eliminating the presence of a temperature signal doesn’t mean that there wasn’t one present in the original collection. The fact that these other researchers found something other than a flat line suggests they are actually looking at something in the data other than pure random noise. Just what they found might or might not be the signal of temperature or anything else related to climate, regional or global.
AndyG55 says:
July 10, 2012 at 4:18 pm
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. ;-))
Ah – linearity breeds contempt!
How far have we come in 90 years of paleo-climatology? This graph has some striking similarities to Huntington’s chart of Californian climate back 2000 years:
http://enthusiasmscepticismscience.wordpress.com/global-temperature-graphs/1924_huntington_civilizationandclimate_p321/
Tree – ring reconstructions may be flawed because trees respond positively to both temperature and moisture, but often if not most of the time these two are inversely correlated, at least as the CET’s record shows:
http://www.vukcevic.talktalk.net/CET-R.htm
Antbones says:
Wow… And just last year you were posting stories about how bad tree ring proxies were… I guess if it fits your agenda it’s ok?
Anthony doesn’t always agree with or support what he posts – he’s making it available for his readers, who then discuss it. And you appear to have missed the numerous posts pointing out that they still don’t accept the tree ring proxies.
Face it, Mann had an agenda to support, whereas a less ideologically-bent view has shown an opposite trend.
One person made tons of money and fame; the others, not so much.
Who do you think is lying?
Look, if a warmist cites tree ring evidence as proof of CAGW, I see nothing wrong with nullifying it with better tree ring evidence. Skeptics are skeptical of tree ring methodology, due to the difficulty of extracting a pure temperature signal. Each extracted signal must be rigorously scrutinized and evaluated on integral and demonstrated merit. No one doubts the signal is there… somewhere… in the noise.
Sorry, Mann made temperature reconstructions, do not pass GO and he does NOT get to collect $200. GK
Have a look at RealClimate – as expected, they love this: the recent tree rings fit the instrumental record, and will handily supercede the Briffa declining sequence.
This proves nothing! Of course the climate change cabal will argue:
1. The data is misleading…
2. The data only relates to N Europe & thus a cooling climate in europe does not mean that [ man made] warming that wasn’t/isn’t happening elsewhere
Yeah right!
“This is what global cooling really looks like…”
Let me fix that headline for you:
“This is what northern Scandinavian cooling really looks like…”
Much better.
But it is not half of the story, because its only JJA, in the plant
growths phase……. in the LIA there were good high summer
temps, due to European dry high pressure weather conditions….
The LIA can really be judged based on the autumn/winter/spring
temps….. taking only JJA, this is talking the LIA down and producing
another hockey stick….JS
Anthony… what can I say? You know what I’m talking about. Five years from now…..
pinetree3 says:
July 10, 2012 at 6:27 pm
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.
It is of course the RealClimate crowd who are the true deniers (of climate history before 1850) and cherry-pickers. They focus myopically on the 20th century temperature rise and ignore similar or larger rises taking place in the palaeo proxy record in this paper at:
100 BC
350 AD
500 AD
740 AD
1200 AD
1480 AD
The point has been made in previous posts here that over the Holocene there have been at least 20 temperature rises comparable to or greater than that of the 20th century.
Congratulations! You managed to get this study misrepresented on FOX News!
I would seem that the Pillars of support for the religion of Mann-made global warming are resting on the soft sand of bad data.
Anthony Watts misleads the audience already in the title of his article:
“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”
However, the temperature reconstruction and the trend of -0.31 K/millennium is for Northern Scandinavia and the Arctic zone, but not for the global temperature anomaly. And conclusions about how the temperatures in Roman or Medieval times compare to present day temperatures can only be drawn for this region from this study, but not for the global temperature anomaly.
And most of the devote followers here don’t notice or don’t care about being misled. They just want to get confirmed their preconceived views.
Although I don’t really understand why the fake skeptics crowd, except the ones who dismiss tree ring proxies altogether, is so excited about this study.
How do the results of the study contradict man-made global warming, as some seem to believe here? If the natural trend due to orbital forcing is cooling, then it rather supports the view that the warming trend in the 20th century, particularly the one since the mid 70ies is largely man-made.
Notable: One of the conclusions of the study is the better agreement (oh, oh!) of the new proxy reconstructions with the results from simulations using state-of-the-art coupled climate models, which take the variation of the orbital parameters into account.
Watts also writes:
“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. ”
These are the kind of personal, inciting statements, which don’t belong in a scientific argument. But this here is just an opinion blog. Anthony Watts doesn’t do any science. Thus, personal attacks against scientists are allowed.
REPLY: Even though this is an insulting and spiteful comment, I’m going to allow it as Dr. Perlwitz is entitled to his opinion. It should be noted that Dr. Perlwitz is on the government advocacy payroll at NASA GISS. His page is here: http://www.giss.nasa.gov/staff/jperlwitz.html
My issue, and the issue with many here, has been Mann’s insistence that the MWP was a small event confined to sections of the NH, rather than broader, perhaps global. Dr. Mann (an the GISS team) has gone to great lengths to obscure and erase the MWP (as was done in the shoddy MBH98 paper), and that’s the issue I’m addressing.
I’m not interested in a discussion, since there is no basis of trust between Dr. Perlwitz and myself, we aren’t going to change each other’s viewpoints. Ever since I found out your boss, Dr. James Hansen, resorted to stage theatrics in June 1988 with Tim Wirth, I have no trust whatsoever in GISS. At one time Dr. Hansen’s work motivated me to do a nationwide project with the National Arbor Day Foundation in 1990 and 1991 to offset CO2 by planting trees with the help of weathercasters nationwide. Now, having seen what he is, I see him and GISS in general as nothing more than funding survivalists willing to distort science as needed to preserve the organization. Following your lead on wordplay, he’s a “fake scientist”, demonstrated by deeds to be mostly an activist now.
As for the “Anthony Watts doesn’t do any science.” comment, I’ll see you in 2013.
Be as upset as you wish. But I’m entitled to my opinion too.
– Anthony
Anthony Watts has done more for honest science than Jan Perlwts and James Hansen put together. Doubled and squared.
Perlwitz says:
“…the temperature reconstruction and the trend of -0.31 K/millennium is for Northern Scandinavia and the Arctic zone, but not for the global temperature anomaly. And conclusions about how the temperatures in Roman or Medieval times compare to present day temperatures can only be drawn for this region from this study, but not for the global temperature anomaly.”
Anomalies are simply deviations from the trend, or from a baseline, or average. Therefore, the only honest comparison is made by looking at the long term trend within its long term parameters. Since temperatures have not broken out above their long term parameters, the only logical conclusion is that the effect of CO2 on temperature is too small to measure.
That trend line shows that temperatures are not accelerating. The gradual rise in global temperatures has not deviated from the long term trend line since the end of the LIA, when CO2 was at ≈280 ppmv. CO2 is now at ≈392 ppmv. But that ≈40% rise in CO2 has not caused an accelerating warming trend.
Thus:
CO2 has no measurable effect on global temperatures. QED, Mr Perlwitz. QED.
[SNIP – like I said, not interested in a discussion right now. Have a nice weekend Dr. Perlwitz, and you too Smokey. I have better things to do than moderate this fight. – Anthony]