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  1. At -80 latitude 12kybp, mean december insolation anomaly is negative, mean june insolation anomaly is neutral, but mean anual insolation anomaly is strongly positive. Something interesting must be happening in spring and/or autumn, can anyone elaborate?

    Comment by Bouke — 16 Sep 2013 @ 5:59 AM

  2. Any idea why error bars are getting substantially larger as present is approached? What’s happened to the Roman and Medieval warm periods? What’s happened to the cooling in between, when 9 m high ice ridges, coming from the Black sea, were towering over the walls of Byzantium (Istambul now)?

    Comment by Berényi Péter — 16 Sep 2013 @ 7:00 AM

  3. @ Bouke
    Fig.1 (Climate forcing reconstructions for use in PMIP simulations of the last millennium (v1.0)9(2011)
    G. A. Schmidt .) Shows the much larger insolation changes around the eqinoxes than the solstices.(since CE 850)

    Comment by gareth — 16 Sep 2013 @ 8:35 AM

  4. On figure 3.

    Why do the error bounds on the right hand side increase?

    Surely with measurement of temperatures, the error bounds must decrease?

    ie. We know current temperatures accurately, but will be unsure of temperatures 10,000 years ago?

    [Response: The error bars on the Marcott et al work are because (unusually) there are less records included as you come up to the present. This is related to the difficultly in retrieving and dating the top of ocean sediment cores, while it is relatively easy to date the the termination of the glacial period (and beginning of the Holocene). – gavin]

    Comment by Nick — 16 Sep 2013 @ 8:50 AM

  5. Berenyi, given your…track record…please show me the supporting data that shows this isn’t just something you’ve once again made up.

    “…when 9 m high ice ridges, coming from the Black sea, were towering over the walls of Byzantium (Istambul now)?”

    Comment by HarryWiggs — 16 Sep 2013 @ 8:52 AM

  6. Dr Schmidt,

    You say that the increase in uncertainty at the far end of the graph is due to few samples available. The authors have indicated that portion of their study is “not robust”. So why use it?

    When the results for the last few decades of a 2 millenial period are uncertain and not robust, including them risks the credibility of the entire study.

    [Response: Our opinions on this will obviously differ, but including the later points along with the uncertainties allows people to assess this for themselves. Plus inclusion of data that overlaps in time but does not have the same uncertainty (i.e. PAGES-2K, HadCRUT4) provides some context. Pointing out where parts of a reconstruction have more uncertainties than others adds to its credibility in my opinion. – gavin]

    Comment by timg56 — 16 Sep 2013 @ 10:13 AM

  7. Marvellous stuff.

    Berényi Péter,

    Can’t you read graphs? There’s a bump between 0 and 1000AD, and the error bounds give enough wiggle room for the MWP and Roman Warm periods.

    Or is it that the wiggle room and bump isn’t large enough for your preconceptions?

    Comment by Chris Reynolds — 16 Sep 2013 @ 10:22 AM

  8. That portion of the data is shown for comparison – of course the instrumental measurements (shown in red in the first graph) are much more reliable for the modern time, as I discuss in the article. -stefan

    Comment by stefan — 16 Sep 2013 @ 10:29 AM

  9. Mon cher M. Berenyi,

    If you read the post carefully, both the reason for increasing error bars, and “what happened” to the Medieval Warm Period and the Little Ice Age are addressed — and they are in fact present in the graph (Fig. 1) — just not perhaps as you expected to see them, but as consistent with a long term trend.

    But I am remiss if my comment is actually troll-feed.

    Comment by Grunter — 16 Sep 2013 @ 11:01 AM

  10. Interesting post. So what about the 5000 year puzzle? You seem to leave this hanging or am I missing something?


    Comment by Axel — 16 Sep 2013 @ 11:12 AM

  11. It would help to have a 10,000 year history of natural and anthropogenic albedo change as well.

    Comment by Russell — 16 Sep 2013 @ 11:17 AM

  12. I ran a Fourier filtering experiment using the Marcott et al reported frequency functions for their processing, and obtain results roughly identical to Grant Foster – any Holocene era temperature changes of a magnitude similar to current warming would indeed have shown up quite clearly in the Marcott analysis. (Not to mention that current warming simply won’t reverse/vanish on the same time-scale as it has ramped up, due to the persistence of CO2…)

    Modern warming indeed appears unique in the Holocene era.

    Comment by KR — 16 Sep 2013 @ 11:44 AM

  13. It appears from the graph (Figure 3 blue line) that the unique rapid rise started in the late 1800′s.

    1.) Does this suggest that humans were already putting out enough CO2 to cause global warming at that time?


    2.) Even though the rapid rise is unique, it may have been natural (from the late 1800′s to 1940 – end of the blue line)?


    3.) Something else… (my eyeballing of the graph was wrong, premise of my question was wrong, etc)?



    Note: this may be a duplicate. I noticed comments making it through moderation time stamped after I’d asked my question. Please delete if my original post actually made it and just hasn’t been moderated yet. Thanks.

    Comment by Tad Boyd — 16 Sep 2013 @ 11:44 AM

  14. If I recall correctly, Marcott using the high frequency noise in the shorter Mann et al 2008 reconstruction to estimate what type of shorter-term variability might be removed over the whole holocene due to coarse proxy resolution. This yields his Figure 3, where they argue that the decade from 2000–2009 has not yet exceeded the warmest temperatures of the early Holocene (5,000 to 10,000 yr B.P.) but it is warmer than 72 percent of the record.

    I wonder if you could do a similar analysis, but look at a frequency density function of 100-year (or 50-year) trends instead of looking at a frequency density function of anomalies. Its not perfect, of course, as there is no reason to think that the Mann et al 2008 reconstruction is really characteristic of shorter term (< 400 year) variability throughout the holocene, but the results might be interesting. I strongly suspect they would show the recent period as somewhat unique.

    Comment by Zeke Hausfather — 16 Sep 2013 @ 12:12 PM

  15. > the top of ocean sedimentary cores

    The top is almost always inhabited — the result is “bioturbation … rapid removal of sediments from the sediment surface (ingestion) followed by injection of this material (defecation) a few centimeters below the sediment surface. This process has significant implications for the age of surficial sediment and for discerning change in sediment contaminant concentrations following change in contaminant inputs.

    In an undisturbed site where nothing lives in the mud, you could get annual or even seasonal layers (varves“).

    It’s not a big problem. It’s one consideration when getting information out of core samples.

    Comment by Hank Roberts — 16 Sep 2013 @ 1:26 PM

  16. I am a 64 year old man in fair health, with chronic progressive aches and pains. But if I take the average readings of my health from the recent thirty years of my life, one has to say that I am vital and strong. (cough, cough)

    And just this morning, I was thrilled to notice the water in my ice cube trays had frozen solid. After I add a little ethanol, I expect to greatly enjoy myself later on. But I dare not use either piece of evidence to prop up a deluded notion that I remain a young man on a cooling planet.

    Cheers !

    Comment by richard pauli — 16 Sep 2013 @ 2:08 PM

  17. And so, unless we are able to do something about climate change, we shall be entering the obcene era.

    Comment by Lawrence Dawson — 16 Sep 2013 @ 5:05 PM

  18. Tad Boyd #13,

    “It appears from the graph (Figure 3 blue line) that the unique rapid rise started in the late 1800′s.
    1.) Does this suggest that humans were already putting out enough CO2 to cause global warming at that time?”

    Yes, but not enough for the resulting global warming to obviously jump out of the random variations.
    For context, here are a couple of graphs featuring relevant estimates:
    You should generally not trust random graphs. Even if there’s a .gov in the URL suggesting they’re not simply made up, you shoudn’t trust the impression you get for eyeballing graphs that may have been chosen to produce a particular impression. However, this being realclimate, you may hopefully trust that misleading or badly outdated data will be shot down.

    Note that the more CO2 there is in the atmosphere, the less impact every additional mole has.
    Also note that deforestation had a large impact on atmospheric CO2 concentrations relative to the burning of fossil fuels before the end of the 19th century.

    “2.) Even though the rapid rise is unique, it may have been natural (from the late 1800′s to 1940 – end of the blue line)?”

    I’m not crazy about the word “natural” in this context because of the large impact of pre-industrical human activity.

    Obviously temperatures were already affected by elevated levels of CO2.
    But because there have been a lot of random variations, I’m not sure the circa 1875-1940 global warming was all that rapid or unique unless you consider it as part of the longer industrial-age warming trend which is of course remarkable indeed.
    But no doubt other commenters would have something more cogent to say on the matter.

    Comment by Anonymous Coward — 16 Sep 2013 @ 5:42 PM

  19. Tad Boyd @13 — Anthropogenic changes to so-called natural climate trends began to be quite sizable with the clearing of forests in Europe and North America for ever increased agricultural fields. Coal, Satan’s cobbles, started being burned in appreciate quantities by 1750 CE and there was already appreciable heavy industry by about 1850 CE.

    That the trend in global temperature only becomes positive around 1880 CE is an indication of what is called climate inertia combined with the declining orbital forcing which had to be overcome.

    Comment by David B. Benson — 16 Sep 2013 @ 8:56 PM

  20. “What’s happened to the Roman and Medieval warm periods? What’s happened to the cooling in between, when 9 m high ice ridges, coming from the Black sea, were towering over the walls of Byzantium (Istambul now)?”
    There were no ice ridges. And since the walls of Constantinople were 12 meters in height, a 9-meter ‘ice ridge’ wouldn’t ‘tower over them’. There were recorded episodes of the Marmara Sea icing over in the 1st century CE, the 4th century CE, and a succession of frozen sea winters from 800-1300 – but no 9meter ice ridges. Yavuz et. al. “The Frozen Bosphorus”, 2007.

    Comment by owl905 — 17 Sep 2013 @ 2:21 AM

  21. #9

    If you read the post carefully, both the reason for increasing error bars, and “what happened” to the Medieval Warm Period and the Little Ice Age are addressed — and they are in fact present in the graph (Fig. 1) — just not perhaps as you expected to see them, but as consistent with a long term trend.

    Yes, it occurred to me before that the Marcott reconstruction kind of puts the MWP into perspective. Prior to the last century it looks like we had a cooling trend of about 5k years, so it would be expected that temperatures in Medieval times would be warmer than in most of the last 700-800 years and, in the absence of modern anthropogenic warming, warmer than today.

    So if there was a temporary but slight deviation from the long term trend, and throw in a bit of regional variation, then it could well be the case that NH temps in medieval times were particularly warm, even approaching today’s levels (or exceeding them in some locations). But this would not be evidence that warming to the extent we have seen over the last century occurred naturally at that time without any human influence. I guess to be fair that it also counters the argument that the MWP is evidence for high climate sensitivity.

    Is this a fair interpretation?

    Comment by andrew adams — 17 Sep 2013 @ 5:35 AM

  22. Tad Boyd @13.

    Surely the one thing this post is at pains to point out is that it does not accurately propose the level at which temperatures began to turn and thus when “the unique rapid rise started” is also not on offer.
    However I think your point is that the driver of such a rise would have to be strong enough by 1940 to be responsible for the loin’s share of the 0.35C rise that we know from thermometers had occurred by 1940. (Note that HadCRUT4 shows (as graphed here) declining temperatures 1850-1908 and then a 0.47C rise to 1940.) Perhaps you are also wondering how far back such a driver would have a significant impact on temperature so as to start that “unique rapid rise.”

    If C02 is considered as that driver (not a ridiculous idea in principle, although it is more complicated than that as intimated @19) how much forcing and thus how much temperature rise could we expect from our CO2 emissions by, say, 1900 or 1940?
    On the back of a fag packet. From the graph presented by Scripps Institute CO2 measured from ice cores had risen 20ppm by 1900 or 16% of the CO2 rise to date. By 1940 35ppm = 30%. The forcing per ppm is greater at lower CO2 levels and the slower rate of CO2 rise would mean more of the forcing was potentially balanced by temperature rise. But, ignoring that, a simple pro rata rise per ppm yields +0.13C (1900) +0.24C (1940).
    Again very simplistically, if the wobbles from the Marcott et al reconstruction are seen as a possible size of natural low frequency wobbles of the order of 0.1C peak to peak, the idea that “the unique rapid rise” should have started before 1900 would fit with CO2 as the dominant driver. The size of natural high frequency wobbles may or may not be why HadCRUT4 shows a minimum in 1908. Certainly by 1940 a CO2 forcing would be dwarfing those natural low frequency wobbles and this appearing as a significant feature on a graph of millennial temperatures.

    Comment by MARodger — 17 Sep 2013 @ 6:33 AM

  23. This lengthened reconstruction of global temperatures is no longer forming the shape of a hockey stick. Given hockey sticks are traditionally made from Mulberry and that Mulberry has a characteristic of growing slowly when mature (at least under natural circumstances), would it be fitting to christen the lengthened reconstruction developed here by Marcott et al as the “Mulberry Bough”.
    Although myself I would end the trace at 2012 with just a marker to show the 2100 projection, it surely would remain plain to any observer with half a brain that the spurt of growth we see on the end of that Mulberry Bough is not natural.

    Comment by MARodger — 17 Sep 2013 @ 6:41 AM

  24. Are there any Geologists claiming that the planet has been warming for the last 11000 years? Were there ever any Geologists making that Claim? And have they revised their position recently similar to the way the Geological Society revised their position statement on recent warming ?

    Comment by FP — 17 Sep 2013 @ 8:37 AM

  25. Here, is the AAPG claiming the earth to be warmer in the last 10,000 years…

    ” In recent decades global temperatures have risen. However, our planet has been far warmer and cooler today than many times in the geologic past, even within the past 10,000 years.”

    ~ What is their evidence of that? Or is their only argument: “Well, it could have happened, it is possible, and it could be hidden because the data is not granular… ” Or do they have real evidence?

    Comment by FP — 17 Sep 2013 @ 9:09 AM

  26. Tad Boyd @13

    Found that Gavin had replied to my question but it was sent to the borehole [#1300].

    [Response: Other people can chime in – but I think it’s more useful to think of the early 1800’s as being a time when shorter term natural forcings (particularly volcanoes and solar) were pushing climate cooler than the long term trend would imply. Without anthropogenic influences there would have been a recovery of sorts but only to the long term trend – what has actually happened is vastly different. – gavin]

    Thanks all for your responses.
    I’d had the idea that more recent (than pre-1900) very high human emissions of CO2 drove global warming (the SUV/Commercial air flight era). I was aware of the idea that human activity much earlier than that had started to bring about global warming but did not know if this was generally the view of actual climate scientists. I don’t usually comment because I’m not qualified to make a point, but occasionally do post a question to try to get clarification on what actual climate scientists believe vs. all the other ideas out there and have gotten good direction here at RealClimate (especially from Gavin).

    From other commenters that were kind enough to respond to my question I’ve gotten – we (humans) were warming the planet (offsetting cooling) early on (1700’s and 1800’s). Gavin indicates we would have seen a recovery of sorts without human influences but not what has actually happened.

    MARodger – You laid out the influences of 20ppm CO2 and 35ppm CO2 increases. (Note – in my reading when Stephan was talking about the unique rapid rise under Figure 3, I was focused on the Marcott et al. blue line and thought that was the context for his description but using HadCRU as the context for the unique rapid rise Stephan is talking about works too as the rapid rise pre 1940 in red, is even more dramatic). Your response helps a great deal to sharpen my clumsy question.

    Stefan and/or Gavin – I was assuming that the 1940 and before portion of the rise (Marcot et al. blue line, but HadCRU red line works too) was at least part of what Stefan was referring to as the unique rapid rise but MARodger has indicated my assumption is off in some manner so any instruction regarding that is appreciated. If my assumption is valid in some sense, is the uniqueness of the pre 1940 rapid rise the result of the human activity part of the 20ppm and 35ppm CO2 increases MARodger discusses?

    Sorry if MARodger’s response should have sufficed. It is possible I am in the <50% brain category. I do appreciate that actual climate scientists are willing to interact at this level helping separate what the scientists believe vs. the rest.



    Comment by Tad Boyd — 17 Sep 2013 @ 10:39 AM

  27. > our planet has been far warmer and cooler today …

    The AAPG authors:

    Their approach starts and ends with politics and money, not climatology:

    Introduction to Geological Perspectives of Global Climate Change
    Power Point Presentation

    Lee C. Gerhard

    History has seen many memorable public confrontations between belief systems and science data. Despite the scientific merit of the data, belief systems are powerful endemic and forces against which science must struggle. Some modern examples are evolution and global climate change..


    Two versions of the presentation are included, one for scientists, without on-slide comment, and one for the lay public with some additional notation.

    These presentations will be updated as new information becomes available.

    The notes for the scientist version contain many of the base references; a reading list, partly annotated, is appended to this introduction.

    So — “evolution and climate change” — I wonder what he means by that?

    Comment by Hank Roberts — 17 Sep 2013 @ 11:02 AM

  28. In Fig 2 I am having a hard time reconciling Mean Dec and Mean Annual. The Mean June makes perfect sense – high insolation in N. Hemisphere extending to Arctic. The Mean Dec does not show high insolation in S. Hemisphere or Antarctic yet the Annual Mean then shows high insolation in Antarctic.

    Also, with the large solar forcing 8-10K ago “more than 30 watts per square meter” (in summer I assume) I would have expected even higher temperatures than modern 20th century. Why is that expectation wrong?

    Comment by James Cross — 17 Sep 2013 @ 12:40 PM

  29. @26
    Quote from that .doc by Lee C. Gerhard:

    The mission of the Intergovernmental Panel on Climate Change (IPCC), a United Nations organization, is not to study causes of climate change, but to document only one cause, human impacts on climate.

    Quote from the resolution that started the IPCC:

    [the UN] Endorses the action of the World Meteorological Organization and the United Nations Environment Programme in jointly establishing an Intergovernmental Panel on Climate Change to provide internationally co-ordinated scientific assessments of the magnitude, timing and potential environmental and socio-economic impact of climate change and realistic response strategies

    When I read these two things, I get the urge to add Lee C. Gerhard to my list of intellectually bankrupt people.

    Comment by Bouke — 18 Sep 2013 @ 4:45 AM

  30. Bouke,
    Care to explain this extract from the “history” page of the site.
    Nothing about NOT human-induced climate change…

    “Today the IPCC’s role is as defined in Principles Governing IPCC Work, “…to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. IPCC reports should be neutral with respect to policy, although they may need to deal objectively with scientific, technical and socio-economic factors relevant to the application of particular policies.”

    [Response: Understanding “the scientific basis of the risk of human-induced climate change” obviously requires knowing the context of natural climate change and variability – explaining the amount of space in the IPCC reports given to issues associated with paleo-climate, ENSO, the AMO, signal-to-noise calculations, detection and attribution etc. This idea that IPCC doesn’t look at internal variability or natural forcings is just bogus. – gavin]

    Comment by Romain — 18 Sep 2013 @ 6:31 AM

  31. Why is the right hand side figure not in the center of the error bounds?

    Comment by Nick — 18 Sep 2013 @ 9:10 AM

  32. Further to comment @25-27.
    The actual slides are in this pdf. There is another version of notes & slides here. It dates back to 2007 and is very silly stuff.

    Comment by MARodger — 18 Sep 2013 @ 10:56 AM

  33. AAPG:
    collection of papers and graphics.

    There may be some interesting material, e.g.

    Modeling Holocene Primary Productivity Changes in the Barents Sea

    we investigate organic carbon sedimentation patterns and surface water productivity changes in response to Holocene Previous HitclimateTop variability in northern high latitudes. We studied 197 surface sediment samples, 10 short (ca. 10-30 cm long) and 2 long (3-4 m) cores representing the last 10000 years in the western sector of the Barents Sea between Spitsbergen and the Norwegian mainland.

    The Barents Sea is a shallow (mean depth ca. 200 m) Arctic Ocean shelf sea which is partially covered by sea ice in the northeast in the winter. Warm, saline Atlantic water (AW) enters the Barents Sea in the southwest and flows east- and northward until it is subducted under cold, fresh Arctic water (ArW) which enters the Barents Sea from the northeast and flows southwestward. The region where the AW is subducted under the ArW is called the Polar Front (PF). Its position is mainly topographically controlled but also depends on the relative strengths of the two water masses. This is also the region of the winter ice margin. Previous research has shown that the Barents Sea is one of the most productive shelf seas in the world.

    We use OF-Mod 3D, an organic facies modeling software developed by SINTEF Petroleum Research, to reconstruct PP changes and organic carbon accumulation across the western Barents Sea throughout the past 10000 years. OF-Mod 3D is a predictive, process-based, forward-modeling tool used to calculate organic matter preservation in a 3D grid throughout the modeled domain. The surface sample data set is used to calibrate the model to the present-day situation and we will show the spatial distribution of modeled PP throughout the Barents Sea region. We include the position of the PF in the model as a northern boundary for PP during the winter and compare organic matter accumulation in the presence and absence of sea ice.

    AAPG Search and Discovery Article #120098©2013 AAPG Hedberg Conference Petroleum Systems: Modeling the Past, Planning the Future, Nice, France, October 1-5, 2012

    Comment by Hank Roberts — 18 Sep 2013 @ 3:19 PM

  34. #27–“I get the urge to add Lee C. Gerhard to my list of intellectually bankrupt people.”

    No obvious reason to resist the urge.

    Comment by Kevin McKinney — 18 Sep 2013 @ 3:33 PM

  35. Well, look around there first, don’t take the worst you can find and write off the rest unseen. That one’s a dinosaur, you expect those. They’re holdovers from the Antideluvian Age, er something.

    Petroleum geologists have to understand modeling and climate.

    Comment by Hank Roberts — 18 Sep 2013 @ 6:07 PM

  36. Keying off 26 and 27:
    Gerhard’s attempts a smear with “The mission of the Intergovernmental Panel on Climate Change (IPCC), a United Nations organization, is not to study causes of climate change, but to document only one cause, human impacts on climate.”
    In a lay-down, he’s right. Our climate would not have nearly the focus, the research, the reviews, and the controversy, if it was just ‘understanding it all’. But while Gerhard thinks he’s exposing a secret agenda scam, he’s actually admitting that he can’t join the dots. He doesn’t understand that rising GHG pollution is contributing to a disruption of the climate so geologically sudden and ubiquitous in extent, that the parallels best matching it are extinction events. That’s exactly why the IPCC synthesizes a global state of the change every X years. Gerhard displays a kind of Victorian attitude that somehow if the IPCC just stopped talking about, it would be less of a problem.

    Comment by owl905 — 18 Sep 2013 @ 11:54 PM

  37. MARodger @ 23: I was thinking the same thing, but what I see is more like a kind of ergonomically made scythe with a curved handle. (links to images seem to be too long for the filter)

    Meanwhile, on the topic of paleo-climate, Hansen has a new piece out in Philosophical Transactions of the Royal Society A:

    “Climate sensitivity, sea level and atmospheric carbon dioxide”

    Pretty sobering stuff. Here’s the discussion at CP:

    Comment by wili — 19 Sep 2013 @ 2:59 AM

  38. #23 >Given hockey sticks are traditionally made from Mulberry…

    Hockey sticks were never made from mulberry…originally made from hop hornbeam (Ostrya virginiana), then later ash, birch, poplar, and willow. Mulberry is not a commercially viable wood.

    Comment by kainin — 19 Sep 2013 @ 7:22 AM

  39. #38–My initial reaction, too, but you’re not thinking of the correct type of hockey for this context:

    “1860s Hockey taken to India. Stickhead made shorter; move from Ash to Mulberry timber for the stick head.”

    Comment by Kevin McKinney — 19 Sep 2013 @ 7:41 AM

  40. Gavin,
    “This idea that IPCC doesn’t look at internal variability or natural forcings is just bogus.”
    Yes it’s bogus. Of course they look at it. Whether or not they FOCUS on it is the question.
    What is behind the quoted paragraph when you read it at face value is that this internal variability is just background (proof is, it’s not even mentioned). They say they assess impacts, mitigation and adaptation of HUMAN-induced climate change. Implying that the IPCC is here to confirm a preconceived theory/idea: HUMAN-induced climate change is the most important to care about. IPCC is not here to care about the impacts of natural variability. The scope of work is clear.
    I guess it is because internal variability had already been found to have negligible impact compared to human-induced at the time IPCC was created. But then I hear people saying: it’s hard for IPCC people to question the premises on which it has been created.

    [Response: This is just very strange. The IPCC is indeed designed to focus on the potential for anthropogenic impacts on climate and I don’t see what is so bad about that. The answer might well have been that there weren’t any important ones. Other review panels (on the Supersonic Stratospheric Transports etc.) come up with not much and are generally set aside – this happens all the time. The IPCC premise is that there is a potential issue worth investigating (a true statement), not that climate sensitivity is some fixed number or that natural variability is negligible. The idea that scientists would work on an assessment that they knew to be pointless is nuts. It’s not like these things are fun. – gavin]

    Comment by Romain — 19 Sep 2013 @ 11:25 AM

  41. Can anyone point me to articles discussing the accuracy of the various proxies themselves? I apologize for my ignorance on this, but to me it seems our understanding of the relationship between the proxy data and temperature should be calibrated and tested against the observed temperature record. The error bars seem to indicate that we know the exact global temperature within 0.2 degrees C 1000 years ago, but where we have actual temperature data, the error margin is more than a degree (which more than covers the observed warming).

    In short, do the error bars indicate that science is 95% confident in the real global temperature to within less than 1 degree C for the last few thousand years, or that it is 95% confident that the proxies, using the best available techniques to calibrate calibrate with global temperature, is accurate to within 1 degree C?

    Comment by David C. — 19 Sep 2013 @ 3:45 PM

  42. @41 – Climate proxies

    Comment by owl905 — 20 Sep 2013 @ 1:04 AM

  43. > David C.
    An explanation of that will either assume you did pass Statistics 101, or that you did not. Have you that background in statistics already? If not, some background is needed.

    You’ve run into a problem that confuses a lot of people.

    in 2005, a team led by Sarah Belia conducted a study of hundreds of researchers who had published articles in top psychology, neuroscience, and medical journals. Only a small portion of them could demonstrate accurate knowledge of how error bars relate to significance. If published researchers can’t do it, should we expect casual blog readers to?

    Confidence Intervals
    First off, we need to know the correct answer to the problem, which requires a bit of explanation….

    No, I’m not going to try to explain it, I’m a student here myself. Just sayin’, this is an area that takes serious effort to get even a fair idea of what they’re really saying.

    None of your paraphrases above seems, to me, close to the mark.

    Comment by Hank Roberts — 20 Sep 2013 @ 8:40 AM

  44. Tad Boyd @26.

    You do present your enquiries in an interesting way, so I don’t know but perhaps this might help. (Note that I am by no means a “climate scientist,” actual or otherwise.)

    Because Marcott et al only shows long-term fluctuations, a robust comparison between the blue shoot at the end of the Fig 3 trace and HadCRUT4 is always going to be difficult, especially with the Marcott et al error bars flying off so rapidly. And also note the comment in the post about the “flexibility” of such a “join” although this does not affect the size of the Marcott & the HadCRU rises.
    Perhaps to compare apples & apples, HadCRUT4 should be represented far less precisely, say by just 3 x 55-year averages. 1877 -0.32C, 1932 -0.19C, 1987 +0.16C. The BEST land temperature record suggests that HadCRUT4 is not showing all of this “strong rising trend” because it appeared to start earlier than 1850 in the BEST data. So, like the 5 final green dots from PAGE2K, the 1800-1940 0.25C rise in the Marcott et al blue trace is not far from what we see in the thermometer records.

    Thus far this analysis is fuzzing out the short term wobbles. But you perhaps allude to wondering how much of the pre-1940 temperature rise (presumably the 1910-40 period) is wobble and how much is “strong rising trend.”

    The climate forcings that lie behind the recent wobbles and the “strong rising trend” of HadCRUT4 can be calculated with varying accuracy. The graphs here by Sato et al presents forcings 1880 to date. Note the green plot – this is mostly but by no means all CO2 and that it is not flat back in 1880 (my point @26 with the +20ppm & +35ppm). This green plot is the big positive driver behind the “strong rising trend” but there are also very significant negative drivers.
    It is a major task of climatology to establish these forcings with more accuracy and to marry the forcings with the temperature record. While this work remains incomplete, there exists room for speculation about natural oscillations, speculation that deniers love to over-amplify into reasons for ignoring that green plot in the Sato et al graph. But my take-away from the Sato et al graph is that the green plot is a little too scary to be ignored.

    Comment by MARodger — 20 Sep 2013 @ 11:29 AM

  45. For most of the time covered by these graphs, the thermal mechanism would appear to be more-or-less in a steady state, just quietly following various changes in the forcings. We do not appear to be in a steady state at the moment.
    If we assume the CO2 concentrations stay at the current levels, and if we ignore any positive feedback from methane and so on, is it possible to calculate what temperature we might get to, given enough time?

    Comment by Peter Smith — 20 Sep 2013 @ 8:04 PM

  46. Peter Smith #45,
    That’s the big question; what the sensitivity metric was created for.
    Assuming all forcings (methane, smog and stuff) except CO2 at pre-industrial levels and atomspheric CO2 at the current level, “fast” feedbacks (such as snow cover but excluding the very slow melting of the large ice masses) should get the average global temperature to around 0.52 * sensitivity above the pre-industrial average (if I recall correctly).
    Now sensitivity is likely to turn out to be around 2 to 4 centigrades so (ignoring the many caveats) the answer you’re looking for would be between +.7 to +1.8 on the graph at the top of the page.

    Comment by Anonymous Coward — 21 Sep 2013 @ 3:49 AM

  47. Re Peter Smith @ #45, it is instructive to look at what earth’s climate was like the last time its atmosphere contained 400 ppm CO2, which would be around 3 million years ago during the mid-Pliocene. Global mean temperature then was 2-3C higher than today (and much higher towards the poles), it’s thought there was a near constant El Nino state, and the West Antarctic ice sheet had collapsed, raising sea level by as much as 25 meters. That said, at about this time the Panama seaway closed, which dramatically changed ocean circulation patterns, and uplift of the Rocky Mountains was also taking place, so the mid-Pliocene is far from a perfect analogy.

    Comment by Jim Eager — 21 Sep 2013 @ 1:22 PM

  48. I saw this headline in Science:

    Researchers Wary as DOE Bids to Build Sixth U.S. Climate Model
    “Many researchers are excited about the nascent project, but others worry it could divert resources from existing collaborations.”

    Comment by John L — 21 Sep 2013 @ 8:39 PM

  49. Stefan: nice post, thanks.

    @29 Bouke, see DeSmogBlog entry for Lee C. Gerhard.

    All: keep an eye out for Bill Ruddiman’s Earth Transformed, which is supposed to be out in October (after some confusion about dates.) I think this sheds more light on the last ~8,000 years, relevant both to Marcott, et all and PAGES2K. Compared to past interglacials (when well-aligned, which took a lot of work), the usual slow CH4/CO2 downtrends had been slowed well before the Industrial Revolution started.

    The cover illustrates the part of the story that comes from Chinese rice paddy archaeology and methane curves compared to other interglacials.

    For anyone attending AGU in December, Bill will be giving the Tyndall Lecture.

    Comment by John Mashey — 21 Sep 2013 @ 9:18 PM

  50. considering that humans have now emitted 550 billion tonnes of co2 to date and 1 trillion tonnes emitted brings about the 2C danger threshold (often spoken about by those concerned about such things)and we emit now around 33 billion tonnes rising at 2-3% per annum means that in just a few decades from now the trillion tonnes would have been passed.

    Is it all bad – probably not – but its not all good either and some will definitely suffer from increased flooding and droughts, food shortages and more than likely war as a consequence of such things occurring. It might already be occurring in Syria and Egypt due to food pressures caused by ACC.

    the higher the temperature gets the worse it will probably be although I am sure that places such as southern England can continue to reap the rewards of growing pinot noir and chardonnay grapes for sparking fizz.

    Comment by pete best — 22 Sep 2013 @ 4:36 AM

  51. This is going to be quite upsetting to the MWP climate skeptics that think the MWP was the warmest period ever, warmer than the mid-Eocene high point, than the PETM, than the end-Permian.

    And what do I find in that 1st graph — it was warmer 7,000 years ago (at the -5,000 point) than during the MWP.

    They’re going to get really mad, then work like devils on finding some way to deny it and resurrect their MWP as the warmest of all. :)

    Comment by Lynn Vincentnathan — 22 Sep 2013 @ 11:04 AM

  52. 48 John L quotes Science, “Many researchers are excited about the nascent project, but others worry it could divert resources from existing collaborations.”

    I would think that we could build a new model that would make other models a lot less useful. The higher resolution alone would put it in a whole new league. Even if we had to de-fund an effort or two, at first glance it seems worth it to me.

    Comment by Jim Larsen — 22 Sep 2013 @ 12:34 PM

  53. pete best @50.
    The 550 billion tons is tons carbon (GtC) and includes land use emissions. Without land use it is 365 GtC 1750-2010, according to this CDIAC data with the 2010 emissions figure of 9.167 GtC (excluding land use) = 33.6 GtCO2.

    Comment by MARodger — 22 Sep 2013 @ 1:32 PM

  54. Modeling anything over the century is bound to be uncertain. See this recent NY Times article on population trend.

    The greatest uncertainity is Africa, where population growth is perhaps the greatest welfare issue.

    Like global warming, not much is being done about population growth (China is the exception). That is also true of other major problems looming on the horizon, like drug-resistant microbes and government debt.

    The policy problem is to persuade countries not to downplay such trends because of the uncertainties, and to focus on likely “bad case” scenarios. But such policy making is seldom done, so it should be no surprise that few governments have been persuaded to deal with global warming.

    It is instructive to look at cases where long-term planning to prevent disasters has worked, at least so far – such a restraining the use of nuclear weapons and international economic systems. Both are based on concrete horrible events. The use of atom bonds in Japan, of course. The failure to establish a workable economic/political system after WWI led to WWII, and forced governments to accede to international regulations, such as the Bretton Woods agrements.

    So it’s unrealistic to think that governments will address global warning without definite, clear-cut and specific predictions of disaster. That is not in the cards. It will probably take the actual occurance of horrible events that can be tied to global warming, such as flooding of coastal cities.

    Comment by T Marvell — 22 Sep 2013 @ 2:35 PM

  55. Most people do not understand that humans are part of Nature. Human activity figures directly into all natural processes. We are part of the Biosphere. The equation has to balance. You change one factor by adding or subtracting it to our environment. Be it the Biosphere, Atmosphere, lithosphere or outer space. it will change the existing state of our planet. I do believe that at the current rate that we humans are disrupting natural processes that Nature will take over and put things back into its owen order. The Earth does not need we Humans to survive as planet Earth. I wonder if we have enough smarts to save ourselves as a species.

    Comment by Randy Gertz — 22 Sep 2013 @ 9:28 PM

  56. T Marvell.

    Like global warming, not much is being done about population growth (China is the exception).

    That’s not so. As Hans Rosling points out in this talk, “We have reached peak child”.

    The population increase now is more to do with the number of generations alive at one time rather than the numbers of children being born.

    The biggest thing we can do to control population is to make it easier or more desirable for women to delay marriage/ the birth of their first child. When the average age of first birth increases by 8 or 10 years, from below 20 in far too many countries to well over 25 for example, the multiplier effect through grandmothers and great-grandmothers means that societies finish up with far fewer 4 and 5 generation families. When women need to be 16 or 20, 24 or 30 and 32 or 40 years older than currently to become grandmothers, great-grandmothers, great-great-grandmothers, obviously far fewer families will have a large number of generations as part of their contribution to total population as well as a much shorter overlap time for those that manage very long lives. That’s a far more achievable target.

    (The side benefit being that the option of never having children at all becomes more available or attractive when mature women are not being pressured into presenting their families with grandchildren the moment they got married. One of the great failures of the Chinese program was that they only restricted child numbers and age of marriage. They didn’t do anything about the social and family demands that grandchildren were obligatory and be produced as soon as possible.)

    Comment by adelady — 22 Sep 2013 @ 9:31 PM

  57. adelady, thanks for pointing out the importance of the element of mother’s age at time of first child in discussing population issues. If successfully implemented by whatever means, a global policy that successfully got women to postpone their first pregnancy till after fifty would be the only way to immediately start reducing population without either directly denying any woman the right to have at least one child, or going the route of some form of euthanasia (or even less pleasant methods).

    IIRC, this was one of the strategies used in Bangladesh to get average birth rates down from about 8 kids per mother to 3 or so.

    The US recently spent trillions of dollars bailing out criminals responsible for nearly bringing down the entire global banking system. What if we spent that money offering women around the world a thousand dollars for every year they delay the birth of their first (or next) child? My bet is that for a fraction of the total bailout money you could immediately reverse population rise and send the world fairly rapidly toward a much smaller global population without having to ‘cull’ anyone or ask anyone to take on too burdensome a responsibility.

    Of course, then you would still be left with the other part of the equation–consumption.

    (reCaptcha seems to be getting into the discussion by reminding the guys to keep it “inpants…” ‘-)

    Comment by wili — 23 Sep 2013 @ 2:59 PM

  58. 57 Wili said, ” a global policy that successfully got women to postpone their first pregnancy till after fifty would”

    leave ever so many couples childless, and would dramatically increase ailments in both child and mother.

    30 is a reasonable target, methinks.

    Comment by Jim Larsen — 23 Sep 2013 @ 4:51 PM

  59. Look:
    They have got the fameous bump in the curve starting 12900 years ago and lasting 7-900 years onward, the big freeze, younger Dryas. Discowered in twoo small lakes in Jylland. Denmark.

    This phaenomena has been shown to corelate in time with the lake Agazzis cathastrophy of North America, and even asteroides have been discussed for the cause of it.

    However, as far as I could see, the very fameous Eiffel vulcanism has been totally ignored as an explaination.

    Which was dramatic.

    It did explode quite exactly 12900 years ago and kept on for the same 7-900 years, giving up to 15 meter thick layers of tuffstone near to the Eiffel area, and ash layers are found north to Skåne in Sweden.

    Mankind had to evacuate to Northern Irland, Finnmark, Aserbadschan, Malta, and Portugal.

    But after it had settled, the central EU became very much greener than before, with exellent wines and fruit gardens.

    The tuffstone is interesting. It is more resistant to acid rain than limestone and sandstone. It is light and it can be sawed.

    “VulkanEiffel” and Maria Lach is worthy of a visit. My brother lived at Bonn bad Godesberg and there were very fertile fruit gardens around in the hills, and looking like burnt ashes and glass smellig of sulphur in the quite obviously vulcanic bedrock.

    Thus, think of Eiffel vulcanism next time you write about younger Dryas and the big freeze and check it up. And you may score a peer rewiewed article about it in Nature.

    “Younger Dryas” is named after Dryas octopetala L., which is a very fine flower on the Tundra and in the high mountain plains even today. Rosaceae. And the conscept of “dryas” & the big freeze of younger Dryas discovered in 2 small lakes of Jylland, Denmark.

    OK folks, if this is true, you can keep that Eiffel vulcanism and youger dryas with big freeze as a mark of dramatic events that have not happened since then.

    Comment by Carbomontanus — 24 Sep 2013 @ 10:31 AM

  60. wili wrote: “What if we spent that money offering women around the world a thousand dollars for every year they delay the birth of their first (or next) child?”

    What if we simply spent that money to meet the already existing, huge, world-wide unmet demand for access to contraceptives and family planning services?

    There are tens of millions of women all over the world who already want to reduce the number or frequency of births, but are unable to do so because they lack access to the necessary tools and information.

    Comment by SecularAnimist — 24 Sep 2013 @ 10:41 AM

  61. Carbomontanus, when it comes to volcanic cooling on a *global* scale think latitude: the volcano must be in the tropics for its aerosols to cool both the northern and southern hemispheres. The Eiffel is pretty far north to do so.

    Comment by Jim Eager — 24 Sep 2013 @ 11:04 AM

  62. Jim Larsen: good catch: and obvious typo for ‘thirty’

    SA, I agree.

    Comment by wili — 24 Sep 2013 @ 9:36 PM

  63. 1. Has any correlation been made between space weather, volcanic eruptions, earthquakes and the relatively recent rise in C02/temperature?

    2. Have any of the studies of moon or mars soil shown evidence of recent climate change?

    3. Why does the most recent summer show feel as if we are cooling if we are in global warming?

    Thank You

    Comment by Jim — 27 Sep 2013 @ 7:21 AM

  64. Jim,
    1)No strong correlation exists between warming and space weather. Volcanic eruptions can cool the planet. They don’t explain 40 years of warming.
    2)The Moon has no atmoshpere, so it’s energy balance is purely radiative. Mars’ climate is dominated by dust storms–it cools when there are lots of dust storms, warms when they decrease. The only commonality between Earth and other celestial bodies would be the Sun. Solar irradiance has not changed sufficiently to account for observed warming
    3)Climate change does not imply an end to weather.

    You’re welcome.

    Comment by Ray Ladbury — 27 Sep 2013 @ 10:15 AM

  65. i want each and everyone of you to do this simple experiment.
    just write down when you last saw a frost this year.
    Now cast your mind back to when you can remember when you were a kid
    When did you first see a frost?
    It is pretty simple.
    Yes location will help.

    Comment by jb — 5 Oct 2013 @ 4:01 AM

  66. jb @65 You need to clarify your request a bit, looking for anecdotal evidence of [something?]. When I last saw a frost this year would have been sometime in the spring, I didn’t make a note of the date – when I first saw a frost as a kid would have likely been the first time I was taken outside in the fall, maybe about 1 year old. The former would have been in far western Canada, the latter would have been in Detroit. What does this tell us about . . . anything?

    Comment by flxible — 5 Oct 2013 @ 8:47 AM

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