Mike Mann will have a twitfest on Twitter trying to knock this one down. Data from 91 Northern Hemisphere proxies was used to reconstruct temperature. See reconstruction graph (figure 5) below.
Via The GWPF:
A new paper, looking back at the climate of the past two thousand years, published in the journal “Climate of the Past,” will either cause something of a stir, or provide confirmation of what some regard as having already emerged from the peer-reviewed scientific literature. The title of the paper is, “The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability,” by B Christiansen of the Danish Meteorological Institute and F C Ljungqvist of Stockholm University.
The climate of the past few hundred years is of clear importance because it allows scientists to put today’s warm period into context, and provides some evidence of the influence of the quantity of greenhouse gasses that mankind has injected into the atmosphere. In much literature and during many debates statements to the effect that it is warmer now than it has been for thousands of years are frequently used.
As the authors point out the major problem with reconstructing the climate of the past few thousand years is that the so-called instrumental period – for which we have direct measurements – only stretches back as far as the middle of the 19th century. To overcome this researchers in this paper compile an impressive number of temperature proxies situated in the extra-tropical Northern Hemisphere. There are 91 in total, comprising ice-cores, tree-rings (density and width), lake and sea sediments, historical records, speleotherms, and pollen. All of them go back to 1500 AD and 32 go back as far as 1 AD.
The reconstruction of past climate has improved significantly in the past few years due to the availability of more proxies and better statistical analysis. The authors acknowledge this and point out the differences that are emerging from the reconstructions conducted about a decade ago. They mention two such reconstructions performed by Michael Mann that they say, perhaps typically for the period, show little variability. They add they display, “little evidence for previous temperature anomalies comparable to those of the 20th century.” The authors conclude that previous climate reconstructions “seriously underestimate” variability and trends in the climate record of the past two millennia.
This new analysis shows that the warming we have seen in the late-20th century is not unprecedented, as can be seen in figure 5 (from the paper). Seen in the reconstruction is a well-defined peak of temperature between 950–1050 AD. They also find that the first millennium is warmer than the second.
The researchers conclude:
“The level of warmth during the peak of the MWP (Medieval Warm Period) in the second half of the 10th century, equaling or slightly exceeding the mid-20th century warming, is in agreement with the results from other more recent large-scale multi-proxy temperature reconstructions.”
Ljungqvist et al. also show that, “on centennial time-scales, the MWP is no less homogeneous than the Little Ice Age if all available proxy evidence, including low-resolution records are taken into consideration in order to give a better spatial data coverage.”
In conclusion this impressive piece of research makes a significant contribution to a growing body of evidence that both the global extent of the MWP, and the temperature was similar, or even greater than the Current Warm Period, even though the atmospheric CO2 concentrations today are some 40% greater than they were during the MWP.
Some argue that without anthropogenic greenhouse gasses the world would have cooled in the past few decades. That might be the case, but the statement that it is warmer now than it has been for thousands of years is untrue. The rate of warming seen recently is also not unprecedented.
In the context of climate sensitivity – the real world climatic reaction to increasing greenhouse gasses – and climate model uncertainty, it is an interesting question to ask: if Nature alone in the past can produce temperatures like those we see today, why can’t she do so again?
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The link to the journal is here. Abstract below.
The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability
B. Christiansen1 and F. C. Ljungqvist2
1Danish Meteorological Institute, Copenhagen, Denmark
2Department of History, Stockholm University, Stockholm, Sweden
Abstract. We present two new multi-proxy reconstructions of the extra-tropical Northern Hemisphere (30–90° N) mean temperature: a two-millennia long reconstruction reaching back to 1 AD and a 500-yr long reconstruction reaching back to 1500 AD. The reconstructions are based on compilations of 32 and 91 proxies, respectively, of which only little more than half pass a screening procedure and are included in the actual reconstructions. The proxies are of different types and of different resolutions (annual, annual-to-decadal, and decadal) but all have previously been shown to relate to local or regional temperature. We use a reconstruction method, LOCal (LOC), that recently has been shown to confidently reproduce low-frequency variability. Confidence intervals are obtained by an ensemble pseudo-proxy method that both estimates the variance and the bias of the reconstructions. The two-millennia long reconstruction shows a well defined Medieval Warm Period, with a peak warming ca. 950–1050 AD reaching 0.6 °C relative to the reference period 1880–1960 AD. The 500-yr long reconstruction confirms previous results obtained with the LOC method applied to a smaller proxy compilation; in particular it shows the Little Ice Age cumulating in 1580–1720 AD with a temperature minimum of −1.0 °C below the reference period. The reconstructed local temperatures, the magnitude of which are subject to wide confidence intervals, show a rather geographically homogeneous Little Ice Age, while more geographical inhomogeneities are found for the Medieval Warm Period. Reconstructions based on different subsets of proxies show only small differences, suggesting that LOC reconstructs 50-yr smoothed extra-tropical NH mean temperatures well and that low-frequency noise in the proxies is a relatively small problem.
The paper is not paywalled and be read in its entirety here. (PDF)
Never fear. NOAA has just announced the dedication of a new, 268,000 square foot “Center for Weather and Climate Prediction” in Maryland. It will have a world-class workforce. With foreign scientists participating in said research. They strive to make more accurate environmental predictions.
Can’t wait.
That Vikings settled and farmed a region during the MWP, that this region was then abandoned and hidden under snow and ice for centuries, and that recently there has been enough melt to uncover the old settlements is the sort of proxy for climate that has been well known from long before the current CAGW controversy. That there must be dozens of other similar proxies at the margins of arable land and ice covered regions (eg in the Alps or Himalaya.).
The dips in temperature at 350 AD and 540 AD were enough to finish off Roman civilisation and we could be able to live to see a future dip finish off our own too. There seem to be a lot of people actively working to bring this about.
” We present two new multi-proxy reconstructions of the extra-tropical Northern Hemisphere (30–90° N) mean temperature: a two-millennia long reconstruction reaching back to 1 AD and a 500-yr long reconstruction reaching back to 1500 AD.”
Well, the temperature reconstruction shown in Fig. 5 shows a spectrum of temperature frequencies, which can be related to solar tide frequencies of the bodies in the solar system, and because of this, the temperature spectrum of the two millennia can be simulated using astronomical synodic tide functions of only six couples.
http://www.volker-doormann.org/images/comparison_ghi6_christiansen.jpg
Because of the significant correlation between the reconstructed temperatures and the solar tide functions it suggests that the main effect of terrestrial climate frequencies is of solar system nature (beside volcano effects). An offset of this discovery is the astronomical forecast of terrestrial climate for more than 1000 years in time resolution of month, as mentioned here many times.
V.
Re ; ” kwinterkorn says:
October 17, 2012 at 1:56 pm
That Vikings settled and farmed a region during the MWP, that this region was then abandoned and hidden under snow and ice for centuries, and that recently there has been enough melt to uncover the old settlements is the sort of proxy for climate that has been well known from long before the current CAGW controversy. That there must be dozens of other similar proxies at the margins of arable land and ice covered regions (eg in the Alps or Himalaya.).”
Calder, “The Chilling Stars” – he describes an Alpine pass that shows Roman and Medieval evidence of a an open route in warm times and closed route in cold times.
A little off topic but when people write something like, “Yes we know more then in the past…”, it makes us look uneducated. This statement should have been, “Yes we know more THAN in the past…”.
I know this is nit-picking but if we want to be taken seriously we can’t allow things like this to creep in to our posts. Take a little time to proof read something before you hit send and it will prevent the majority of errors.
Just an observation.
There are many reasons to heed Jeff’s advice. It always interests me how the language of this debate over MWP obscures the uncertainty and variance in the data. We risk substituting our scepticism for just another dogmatism…just look at the title of this post: this paper ‘confirms’ what? The globe was warmer? No. The Northern Hemispere was warmer. Do we already know that?
Indeed, there is the modest question as posed by H H Lamb in the 1960s: In some defined region in the Norhern hemisphere was there a time in the 2 thousands years that was warmer than the 20th century? Then we we might say ‘yes’ for middle england as Lamb did. And maybe for a whole lot of other places too. Dunno about this study, but elsewhere it has been noticed how much variation there is in proxy data for any one region — so even this call remains dubious.
Perhaps it is interesting to look for evidence of a more general, perhaps hemispheric trend. But I am not at all convinced that we are close to finding such a pattern even if we accept the highly dubious regional evidence. The IPCC First Assessment erronously generalised Lambs results — and this has been repeated dogmatically by many sceptics.
One reason for concern is that in both regional and hemispheric results we notice that the period of warming varies across 4 or 5 centuries — from the dark ages almost to the Renaissance. Sometimes it is found before the Millennium. Lamb found it peaking in the high Middle Ages. In this paper the peak is bang on the millennium. Where the peak is in one of these medieval century, the trough is in another. I remain as sceptical of any counter claim as I do to Hockey Stick
More here:
http://enthusiasmscepticismscience.wordpress.com/global-temperature-graphs/
Just how many confirmation studies does it take?
http://www.co2science.org/subject/m/subject_m.php
Lars P.
Note that all of the factors you mention affect the T of Earth via either the albedo or GH effects. Along with solar intensity there is nothing else that is affecting the Earth’s energy ballance.
Also, you should know that RichardsCourtney is a pseudo scientist – very officious but knows very little about the basics of climate change.
Your welcome.. See ericgrimsrud.com
ericgrimsrud says:
“…you should know that RichardsCourtney is a pseudo scientist – very officious but knows very little about the basics of climate change.”
The despicable ericgrimsrud was recently forced to climb down from that canard. Richard Courtney is a peer reviewed, published author in the climate science field. Grimsrud was forced to issue an apology for exactly this kind of lying character assassination.
In reality, it is grimsrud who needs schooling in climate basics, and more importantly, in ethics.
Concering the following post:
‘richardscourtney says onOctober 17, 2012 at 10:25 am
ericgrimsrud: Your post at October 17, 2012 at 8:50 am repeats a falsehood that you know is a falsehood because I have explained the matter to you on two other WUWT threads. I won’t bother to refute it again. STOP SNOWING THREADS WITH FALSEHOODS THAT YOU KNOW ARE FALSEHOODS. Richard’
For the record, Richardscourtney has explained essentially nothing to me that is scientifically correct. While he pontificates on everything and drops reference and quotes calore, I do not believe he has even a basic education in any field of science. I have repeatedly asked him to prove me wrong on that one by providing a resume as all real scientist routinely do. He is “too shy” however, to provide such evidence. While I don’t normally ask others to produce a resume, I have made that request of him simply because he “holds forth” so frequently at WUWT and after finding that most of it is horse pucky, I asked him where he came from.
(REPLY: Mr. Courtney is under no obligation to produce anything. This discussion concerns a warmer climate 1000 years ago. Stop making it personal. ~mod)
[snip – you were warned about making it personal – 48 hour timeout- mod]
To the mods. I know none of us are required to produce evidence of experience. I have just asked some who come on very strongly and frequently to provide it – as I have frequently done. While I don’t agree with you that asking such folks to explain their professional background is “too personal”, WUWT is not my website. It belongs to Watt and you guys call all of the shorts. My motto is the Boss is not always right, but he is always the boss. I participate here only at your pleasure.
ericgrimsrud says:
“…I suppose you are the real thing – with a resume and everything!”
I have been so hoping you would bring this up. Yes, I have a CV, which I have posted on WUWT several times over the years. It is still available in past WUWT threads.
But of course with your constant insults regarding me, I invite you to begin combing through past threads to find it. You may have to go back a year or two. But rest assured that my CV is there and available to you. However, if you think I am going to make it easy on you, then you don’t get my sense of humor: I am amused thinking about you being the busy little beaver, searching through hundreds of threads — only to find what will shut you up.
Start your search, chump.☺
ericgrimsrud says:
October 17, 2012 at 8:50 am
There are three factors that affect the temperature of the Earth: the intensity of solar radiation, the albedo and the greenhouse effect.
This is a step backwards from when people said that there were three elements, ether, water and fire. That is a more scientific statement than the pitiful nonsense you are reciting.
Another thread on this site is about the dim sun “paradox”. 3-4 billion years ago temperature was in a similar range to today – water was in liquid form – despite 25% less sunlight energy. If anything it was warmer back then, not colder.
So a 25% change in solar energy failed to force the climate. So what can force it? 0.039% CO2 in the atmosphere? I dont think so.
ericgrimsrud says:
October 17, 2012 at 7:44 pm
To the mods. I know none of us are required to produce evidence of experience. I have just asked some who come on very strongly and frequently to provide it – as I have frequently done.
>>>>>>>>>>
Yes, yes, we know Eric. You have a Phd in chemistry. You are also a self proclaimed sock puppet for the Union of Concerned Scientists. We know too that you are capable of repeating the party line, but when drawn into a conversation about the actual science of climate, you are quickly over your head. That’s when you start demanding credentials, which is nothing but a blatant attempt to argue from authority. When confronted with facts and logic that you are incapable of refuting, you resort to insults or issue that most devastating of all put downs… and claim that the other person’s argument sounds “fishy”.
You are a tremendous example of the alarmist community. Congratulations.
I wonder if this is the graph that the alarmist Australian govt will put into its climate reports, rather than Mann et al 1998, which it is STILL doing. Or is this a just a vain hope.
Jeff’s warning is indeed very important.
Also berniel’s link is quite entertaining, I’ll repeat it
http://enthusiasmscepticismscience.wordpress.com/global-temperature-graphs/
and add a second one
http://itsnotnova.wordpress.com/2012/09/03/novas-warm-period/ .
Disclaimer: I do not endorse the content behind these two links. But, I think both are relevant within the context of Anthony’s article.
The advantage of being right: in the long run, evidence is MUCH easier to acquire and assemble coherently.
Anthony:
In this thread the odious Eric Grimsrud has demanded my CV. I will not post it here although it is at the end of several papers and articles by me that are posted on the web and so if Grimsrud really wanted it he could find it.
My CV is of no relevance to this thread or to the validity of anything I post on WUWT. The good people here point out the flaw when I say something less than worthy . Similarly for everybody else who posts here.
The posting of CVs would encourage distortion of debate by introduction of the ‘Argument From Ignorance’ fallacy. For example, Tim Ball is more qualified at climatology than me and I am more qualified than Grimsrud. But that does not mean Tim is always more ‘right’ than me (although he usually is) nor that I am always more ‘right’ than Grimsrud (although I have yet to observe Grimsrud being right about anything).
CVs are not relevant to consideration of information and logical argument and they provide bias to such consideration. I will NOT provide mine here.
Richard
Swedish archaeologist Mats G Larsson, who might well represent historians’ current standing, concludes the most likely location (of a likely brief norse settlement south of Newfoundland) is the south coast of Nova Scotia, north of Yarmouth I believe. Keep searching for archeological evidence there locals 🙂
YOU CAN ONLY BELIEVE 50% OF WHAT YOU READ BECAUSE ALL INFORMATION IS BIASED YOU MORONS! CHEERS=M=
Philip Finck says:
October 17, 2012 at 9:24 am
Actually, a Viking settlement was found and has been reconstructed as a historic site on the coast of Newfoundland, Canada.
The Newfoundland site appears to be a base camp set up for commercial purposes not a farmstead. It is not the settlement described in the sagas. Also the route to an from Newfoundland was north the coast along the crossing over where the distance was shorter and the waters calmer. Taking cargo ships via the direct route was too dangerous. That longer safer route would not be possible today because of the ice.
ericgrimsrud says:
October 17, 2012 at 7:10 pm
Lars P.
Note that all of the factors you mention affect the T of Earth via either the albedo or GH effects. Along with solar intensity there is nothing else that is affecting the Earth’s energy ballance.
No & you have brought no argument but used ad-hom, therefore I wll ignore your further posts without valid arguments.
It is logical that the climate was before warmer, not without reason did the vikings farm where now is still frozen. And this is very relevant to the present warming, not without reason try the CAGW-zelots to either change the history or avoid the discussion.
“We live in the coldest period of the last 10.000 years” , says glaciologist, Jørgen Peder Steffensen:
There exist these Canadian conference (Viking Millennium International Symposium 2000) proceedings, including a contribution from Larsson: The Vinland sagas and the actual characteristics of Eastern Canada – some comparisons with special attention to the accounts of later explorers. http://libris.kb.se/bib/9446199