New paper confirms the climate was warmer 1000 years ago

Fig. 1. The geographical locations of all the 91 proxies in Table 1 (top) and of those that correlate significantly with their local temperatures (from HadCRUT3v) in the period beginning in 1880 and lasting to the final year of each individual proxy (bottom). The resolution (annual, annual-to-decadal, decadal) is indicated with the symbols. Proxies that reach back to at least 300AD are indicated in blue.

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.

Fig. 5. Reconstruction of the extra-tropical NH mean temperature (C) based on the gray-shaded proxies in Table 1 reaching back to at least 300 AD. Calibration period 1880–1960AD. Only proxies with positive correlations and a p-value less than 0.01 are used. The included proxies are given in the legend. Thin curves are annual values; thick curves are 50-yr smoothed. Red curves show bias and confidence intervals for the 50-yr smoothed values. From ensemble pseudo-proxy studies mimicking the reconstructions, we have calculated the distribution of 50-yr smoothed differences between reconstructions and target. The biases and the upper and lower 2.5% quantiles are calculated from these distributions. In the figure the biases (full red curves) have been added to the real-world reconstructions. Likewise, the upper and lower quantiles have been added to the real-world reconstructions (dashed red curves). The green curve shows the observed extra-tropical (>30 N) annual mean temperature. The yellow curve show the temperature average over grid-cells with accepted proxies. Both curves have been centered to zero in 1880–1960 AD.

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)

85 thoughts on “New paper confirms the climate was warmer 1000 years ago

  1. Notice that the bulk of warming occurred in the first half of 20th century and present warm peak is not different from that in 1940s. Sorry, no anthropogenic fingerprint there..

  2. When I was twelve, I knew it was warmer a thousand years ago than it is now..
    But then, I was reading the Viking sagas. Perhaps Michael Mann should do likewise.

  3. “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.”

    That one tree Mann loves so much has a great deal to answer for!

  4. Reconstruction of the extra-tropical NH mean temperature (C) based on the gray-shaded proxies in Table 1 reaching back to at least 300 AD. Calibration period 1880–1960AD. Only proxies with positive correlations and a p-value less than 0.01 are used.
    ================
    This still leaves open the question of selection bias which has been shown to create hockey sticks.

    Just because a proxy correlates during the period 1880-1960 doesn’t mean it will continue to correlate outside this period. The correlation could simply be accidental, which means that the selection process is amplifying the noise instead of reducing it.

    This was the criticism of the Mann methodology and the more recent Southern hemisphere hockey stick that was withdrawn prior to publication after the problems were identified on Climate Audit.

    It is a statistical error that is well recognized in fields outside of climate science, such as statistics. Formally it is known as “Selection on the Dependent Variable”. It is a statistical no-no. It is like division by zero, you can prove anything true. 3/0 = 2/0, therefore 3=2.

  5. correction:
    It is like multiplication by zero, you can prove anything true. 3*0 = 2*0, therefore 3=2.

  6. new? if you call 6 to 12 months new. Did Mann try to knock the previous C&L or L papers down? I can’t remember? C&L12 isn’t too different from some of the previous reconstructions. Furthermore, if you look at their Figures 2,3 and 10, you see that their results are far from claiming “universal northern hemispheric warmth”. You also see the obvious mismatch with the observations. The most important point of the paper is: It shows that we really don’t understand the origin of the century of (regionally rather extreme) warmth at the change of the millennia.

  7. it is a shame that we are only now rediscovering what we already knew decades ago. Climate is hugely variable with these apparent peaks and troughs and todays temperatures are nothing out of the ordinary.

    We must assume that the non warming of today over historic temperatures is because the concentration of co2 ceases to matter after around 280/300 ppm. In other words that apears to be the high spot of the logarithmic curve.
    tonyb.

  8. Their plot looks much like what I found in just the ice core data. See slide 49 in http://www.kidswincom.net/climate.pdf. Atributing the temperature rise since 1850 solely to anthropogenic emissions is not statistically probable because the rise in anthropogenic emissions is covarient with natural longterm cycles that the authors are attempting to identify. Quantifying the relative contributions is more difficult. http://www.retiredresearcher.wordpress.com.

  9. One thing that strikes me about this proxy is the speed of the temperature increase 1000 years ago. We have been told that it is not just the warming but the rate of increase that is alarming.
    It seems from the graph that the warming 1000 years ago, looks just like the modern warm period.

  10. Anybody who read history either professionally, or as an ameteur, or was taught it in schools, who is 40+ years of age, knows it was warmer a thousand years ago than it is today! People have short memories indeed! It is really something when in a 16 year old’s science GCSE paper they get a multiple choice question about what burning fossil fuel causes, of course the box against “Global Warming” is the required answer. Frankly, the question is generally irrelevent as the question is one of many in the examination, & is indeed only there to promote the propaganda of AGW into vulnerable & easily shaped young minds! In this country brainwashing with political propaganda is illegal, just don’t tell the Guvment that & never mention it to the 13 year long Imperiously Socialist New Labour from 97-2010!

  11. ****
    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….
    ****

    I don’t think that’s going far enough. Greenland & other N Atlantic regions (at least) were much warmer during the MWP than now.

  12. If you look at it like a stock chart, there is a range-bound downward trend line. Around 1950 the curve breaks the trend and escapes the range. If I were a momentum investor, I’d buy that stock.

  13. There is so much anecdotal evidence of both the Medieval Warm Period and the Little Ice Age, both in contemporaneous accounts and literature, that Mann’s work should have been called into question just based on that evidence. The fact that it wasn’t, the fact that it was embraced whole heartedly by the majority of climate scientists and the greenie leftists, shows just how unscientific climate science is.

  14. But they didn’t use the sacred bristlecones, and nor did they process the data with the holy algorithm of Mann.

  15. As others have mentioned above, it is too bad that what we used to know is now a revelation in the context of the false Mannian climate perspective that is the alleged current consensus..

  16. Ooooops. Yamal is there and prominent. Fortunately, the methodology apparently doesn’t mine for hockey sticks does’it? I’m wondering what weights is assigned to Yamal?

  17. Juice says:
    October 17, 2012 at 8:05 am
    So…proxies are ok now.

    Proxies and anecdotal evidence are all that we have and both have their limitations. Yet, using a wide variety of proxies over a wide area with good statistical analysis makes proxies more valuable and scientifically meaningful. When they match with the anecdotal evidence, proxies become even more reliable.

    The problem with Mann and the Team is not that they used proxies, but that they primarily relied on tree rings and very bad statistical analysis. Plus they simply dismissed the anecdotal (historical accounts) evidence that indicated they were wrong. Oh…and Mann was extremely arrogant and obnoxious in defending his horrible science work!

  18. I recall a divergence controversy on the location of Viking North America settlement during the MWP based on narratives. Their estimate of latitude, they sailed by latitude, put the settlement in Massachusetts or maybe a little north. The description of the flora and fauna put it in New Jersey or a little south. This difference has never been reconciled which made the search for physical evidence of the settlement even more difficult.

  19. There are three factors that affect the temperature of the Earth: the intensity of solar radiation, the albedo and the greenhouse effect. Various events that have occurred on Earth (such as volcanoes or the lack of volcanoes just to mention possibility) can affect at least two of these variable. We do not know as well as we do today what was happening over the entire planet say 1,000 or so years ago. So it is therefore quite possible that temperatures were either higher or lower than today and it is also very possibly that we cannot know why because of a lack in relevant information concerning the past. From the Ice Core Record, however, we do know that CO2 levels did not differ then from their preindustrial levels – so just perhaps a warming was caused by lower particulate matter in that atmosphere, a possibility that we cannot assess because of a lack of information concerning that period.

    My points is: today we know many times more about existing conditions and events around our planet. We do not have comparable knowledge concerning the past – only bits and pieces in comparison. Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.

  20. This study is excellent confirmation of what geologists have been saying for years based on the oxygen istotope measurements made by Stuiver and Grootes (1997) on the Greenland GISP ice cores. The past really is the key to the future! In order to understand where climate is heading, we need to know where it’s been. This study should put to rest any doubts about the natural variability of climate, independent of CO2. Most of the warm and cool periods show up well in the ice core record and have been confirmed by historic records, both human and glacial.

  21. if AGW is true, should we not see a drop in warming in Europe following the Black Plague in the 1st half of the 14th Century? Just askin

  22. Don E says……”I recall a divergence controversy on the location of Viking North America settlement during the MWP based on narratives”
    Actually, a Viking settlement was found and has been reconstructed as a historic site on the coast of Newfoundland, Canada.

  23. Paper also raises the question, Is it acurate to state that the last decade is the warmest decade in the last 1000 or 2000 years? Given the resolution in the proxies vs the electronic measurements of the last couple decades, probably not.

  24. Juice says:
    October 17, 2012 at 8:05 am

    So…proxies are ok now.

    A tad disingenuous, don’t you think? The original hockey stick proxies were twelve trees from one site in Siberia, and the addition of one particular tree created the blade. This paper uses “91 in total, comprising ice-cores, tree-rings (density and width), lake and sea sediments, historical records, speleotherms, and pollen.” The samples were also taken from all over the extra-tropical Northern Hemisphere. Apparently they also did not tack on the observed temperature record when the proxies diverged from what they wanted to see.

    I have my doubts about proxies as well; however, when you use so many different kinds from around the globe, I’d hope that you’d get something other than red noise.

  25. “The reconstruction of past climate has improved significantly in the past few years due to the availability of more proxies and better statistical analysis.”

    Isn’t this pretty much what you get with Mann’s data when short-centered principal component analysis is not used?

  26. Don J. Easterbrook says:
    October 17, 2012 at 8:59 am

    This study is excellent confirmation of what geologists have been saying for years based on the oxygen istotope measurements made by Stuiver and Grootes (1997) on the Greenland GISP ice cores. The past really is the key to the future! In order to understand where climate is heading, we need to know where it’s been. This study should put to rest any doubts about the natural variability of climate, independent of CO2. Most of the warm and cool periods show up well in the ice core record and have been confirmed by historic records, both human and glacial.

    Former geology student here…. Yep!. It always annoyed me that the climate gurus were so insistent to swipe away all evidence of the past based on sound geologic methodologies, and substitute that with their own brand of short-term /short sighted science. Note that I’m not referring to all of climate science and scientist, but the ones who came to dominate the political landscape… You know the names.

    PS. Just wanted to throw this out, that I agree with this post by Gavin. We can only be effective if we make sure we also are skeptical of claims that might favor our skeptic bent.

  27. Fred, your equation’s proof says that 0 = 0, not 3 = 2. Regardless if you divide or multiply by 0. The integer 3 or 2 can be replaced with x = any value, because the value of that integer doesn’t matter. They could even be the same value. Therefore, when your calculation is simplified, it will be 0 = 0. The “logic” your statement tried to use is not logic but is an emotional trick that can be played on simpler minds.

  28. ob says:
    October 17, 2012 at 7:31 am
    The most important point of the paper is: It shows that we really don’t understand the origin of the century of (regionally rather extreme) warmth at the change of the millennia.

    We can be pretty sure that it wasn’t SUVs or power stations ;) Apart from that, how dare you suggest that something affecting climate might be “not understood”? Remember, the whole of current climate science is built on “it must be … because we don’t know what else it might be”.

  29. In standard published research, inclusion criteria are set to determine which studies merit meta-analysis. That Mann’s study was not is an idictment against it. Burn!

  30. Most people think a Warm Globe is a better globe, and they are right. The warming of the globe ended years ago.

  31. Alan the Brit, I fit that demograph, I was lucky enough to attend a grammar school before the left killed them, we were taught, from print (that is why the lefts big heroes burned all the old thought books) about the Romans growing grapes over all of England and the Vikings naming Greenland, and not because they were colourblind ! Then we had lithographs of the thames ice fairs climate changes without our help! I have noticed the lack of common sense in most things green (not the least when I lived in Cornwall and we had one of our usual gales the only thing stationary in the whole county was the wind turbines !)

  32. I think that was kind of his point Pamela. The analogy was that you can prove anything true if you use faulty logic. If I choose to only analyze data with a strong statistical correlation to x, should I be surprised that the logical conclusion is analyzing the data shows it has a strong statistical correlation with x. If I use the 3*0 = 2*0 example to prove 3=2, it is faulty logic. It may be different faulty logic than confirmation bias, but both are still logical fallacies in the end.

  33. 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

  34. Mann doesn’t need to have a twitfest. He can claim

    1. New data, new view. Mine was valid with the data I had.
    2. If not for my prodding, this new work would not have been done. I initiated Good Things.
    3. Yesterday doesn’t matter. Today the situation is different. Yesterday the sun did what human beings are doing today.
    4. I have research grants pending to expand on my previous work. Talk to you later when I have gone beyond what doofus has done. I expect validation of what I did.
    5. It’s all in my book. Buy another today.

  35. This work is not a problem for Mann, there is always the fall-back of claiming that becasue the data does not cover ever square inch of the planet it means nothing , of course proof of ‘the cause ‘ only requires one magic tree but that is the way climate ‘science ‘ works .

  36. Juraj V. says:
    October 17, 2012 at 7:06 am
    “Notice that the bulk of warming occurred in the first half of 20th century and present warm peak is not different from that in 1940s. Sorry, no anthropogenic fingerprint there.

    Yes… and no need to invoke the special ‘Nature Trick’ as perfected by the IPCC CAGW consensus cabal of climatologists.

    It is also becoming obvious that without some serious ‘bending’ of the modern instrument global temperature data-sets that real temperature is much cooler than indicated. We are already over the global peak and on the toboggan ride of the decline. All the extra CO2 seems to have had little or no impact.

  37. The Earth and the sun do it together.
    From the paleomagnetic data (far more accurate then tree rings) it is possible to go back 2 millennia with an error of plus/minus 25 years around 0 BC. We don’t exactly know intensity of the solar activity (10Be and C14 are both affected by precipitation – climate factor, with a danger of circular reasoning).
    Thus to take an even solar output (Dr. S would approve) than we are left with the paleomagnetics as a single factor giving reasonable correlation

    http://www.vukcevic.talktalk.net/LL1.htm

    In the more recent times we have good sunspot count and the accurate geomagnetic records (actual measurements initiated by Gauss) from which a more accurate reconstruction is possible:

    http://www.vukcevic.talktalk.net/GSC1.htm

  38. ericgrimsrud says:
    October 17, 2012 at 8:50 am
    […] My points is: today we know many times more about existing conditions and events around our planet. We do not have comparable knowledge concerning the past – only bits and pieces in comparison. Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.

    Eric, there’s a huge logical disconnect in your statement.

    While we may well “know many times more” about current conditions, the conditions that (by your own admission) we DON’T know about from the past are still able to influence climate by as much, if not more, than the recent warming. Since that demonstrate clearly that we DON’T know about all the natural factors capable of producing such warming, the logical conclusion is that information like this seriously damages any confidence we can have about what’s happened recently.

    Remember, the only reason the science places such high confidence on the effect of CO2 is because there’s “no natural explanation” for warming of this speed or magnitude. Clearly, if this work withstands scrutiny, there ARE natural explanations. The fact we don’t know what they are, or how they work, doesn’t mean they don’t exist!

  39. I want to caution everyone about these results. Besides the fact that there is no such thing as a reasonable temperature proxy that I am aware of, there is a clear pattern of regressomatic sorting in this curve.

    The curve is nonsense.

  40. 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… Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.

    Pretty simplistic way at looking at the climate. You ignore for instance ozone variability. Ozone is warming from direct solar radiation influencing the energy budget of the atmosphere. Ozone can be influenced by natural variation or by solar UV – which can have huge variations even with stable solar radiation intensity.
    You ignore the multidecadal natural oscilations like AMO

    http://upload.wikimedia.org/wikipedia/commons/b/b4/Atlantic_Multidecadal_Oscillation.svg

    or Arctic Oscilation or ENSO.
    What do you mean with albedo? Hopefully not an “albedo constant” – see also Earthshine project:

    http://www.bbso.njit.edu/Research/EarthShine/

    The albedo is variable and we do not know many factors that are influencing it, let alone measure it properly.
    Yes we know more then in the past, but our knowledge is far from being complete, as Richard explained you before, repeating again something that has been shown to you to be wrong does not make it right. So trying to understand what caused the climate variability in the past does have a lot of importance for our understanding of what can cause the climate variability today.

  41. ericgrimsrud says:
    October 17, 2012 at 8:50 am

    My points is: today we know many times more about existing conditions and events around our planet. We do not have comparable knowledge concerning the past – only bits and pieces in comparison. Thus we should not let our lack of understanding of past climates diminish our confidence in what we do know about our present climate and that of the last 100 years during which modern science bloomed and has provided an unprecedented abundance of information pertaining to climate.

    That is not a well-taken point. The idea that we “know” more about the present is mistaken. We have more contemporary measurement. The principle of uniformitarianism has not been suspended, so while Lyell argued that we could, based upon observations of present geological processes, understand much about the past, the converse must be true as well. Any processes operating in the past must also be operating now. No physics or chemical laws have been recently suspended in nature.

    In order to sort out natural effects from anthropogenic effects, we need to understand HOW those natural effects operate. Any evidence of a recent anthropic effect must be superimposed upon the standing natural signal. The sole justification that Mann and the team had for stating that recent warming was “unprecedented” was founded on the assumption that they had actually discovered the signal of anthropic influence and had a valid physical theory to explain it. This is why in the Climategate emails there is concern that the MWP is not disappearing neatly in new data. If it doesn’t vanish with “better” data, then the argument that current warming is unprecedented is unsupported under the uniformitarian principle. If the rates of change are not importantly different between past and present episodes of warming, then rate changes or speeds are not “unprecedented” either. In short, there is then no demonstrable evidence of an anthropic signal in the climate and climate proxy data.

    The fact is that over any geological span of time there is no indication of a strong correlation between CO2 and temperature that indicates a causal linkage, other than evidence that warming oceans discharge CO2 and cooling oceans absorb it, which is what ice core data appears to show during the Pleistocene. At significantly longer or shorter time frames even that mostly vanishes into the effects of other, not so well identified processes at other scales.

  42. 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.

  43. 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.).

  44. 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.

  45. ” 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.

    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.

  46. 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.

  47. 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.

  48. Jeff Condon says: I want to caution everyone about these results.

    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/

  49. 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

  50. 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.

  51. 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)

  52. 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.

  53. 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.☺

  54. 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.

  55. 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.

  56. 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.

  57. The advantage of being right: in the long run, evidence is MUCH easier to acquire and assemble coherently.

  58. 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

  59. 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 :-)

  60. 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.

  61. 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:

  62. 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

  63. One century before and after the maximum of the MWP it was much colder, showing how relatively quick these natural oscillations may happen.

  64. The amazing thing about this paper is that it includes a lot of flawed proxies familiar to Climate Audit readers. There is Yamal, Avam-Taimyr and Tornetrask. Yet despite this the global warming period re-emerges. How much more significant will natural fluctuations in climate appear if the biases in the individual proxy studies could be eliminated?

  65. After more consideration, I think this paper is even more significant that I first realized. A tenet in the scientific method is to reject the null hypothesis. In other words, for a new theory such as AGW to be accepted one must eliminate all natural causes as an explanation for the observations.

    This new paper shows our current temperatures are within naturally occurring phenomena. Even if we can’t explain the cause, we can still say it’s not unusual. Therefore the AGW theory cannot be accepted, purely based on the scientific method.

    http://en.wikipedia.org/wiki/Null-hypothesis

    Unless someone can find a problem with this new paper, the real deniers seem to be those that refused to accept the scientific method. Maybe CO2 can warm the planet, but this new paper undermines their theory. They need something more than the correlations and something causal that cannot be refuted.

  66. Jim;

    This new paper shows our current temperatures are within naturally occurring phenomena. Even if we can’t explain the cause, we can still say it’s not unusual. Therefore the AGW theory cannot be accepted, purely based on the scientific method.

    Not to be too snarky, Jim, but was this really your first clue? It has been clear from early days that the off-handed dismissal of natural variation, while simultaneously acknowledging little or no understanding of its major components, was outrageously wrong. Then Kevin Trenberth tried to assert that the AGW speculation should be taken as the Null Hypothesis unless some other idea were first proven.

    Various ploys, like trying to make the late 20th C warming look steeper than earlier ones were attempted, but really just depended on post-facto selective comparisons. This paper is no surprise.

    • Brian, *I* didn’t need a clue. I’ve been a “denier” for more than ten year. I’m aware of Trenberth’s claims. I’m equally aware of the “ploys” to make the current temperature records biased to support the AGW theory. My question is directed to those consenting scientists. This “paper is no surprise” but this is also the first solid 2000 year reconstruction of temperatures, is it not? This paper, more than any other data I’m aware of, contradicts the claim the current warming is unpredicted or even unusual. If you have other such data, please mention it. You don’t have to convince me. I’m saying we have the best evidence yet to convince them!

  67. Jim;
    To convince them? Not possible. After investing so much in their scientific-politico scam, and receiving such munificent rewards from their efforts, they are quite impervious to arguments. They will have to be crushed, not convinced.

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