20 years of hockey sticks

I wrote this post and then, after a discussion with Kevin Anchukaitis on Twitter, I took it down. I was tempted to not repost it, but thought I’d rewrite bits and have another go. I keep forgetting how controversial this topic can be.

It’s almost 20 years since the publication of the first hockey stick paper (Mann, Bradley & Hughes 1998). In case people don’t know, the hockey stick refers to millenial temperature reconstructions that look a bit like a hockey stick; a period of centuries during which temperatures appear reasonably flat, or cool slightly (the shaft), followed by a period of rapid warming starting in the mid-1800s (the blade). This rise also began at around the same time as we started using fossil fuels, providing evidence that our use of fossil fuels could be impacting our climate. The first reconstruction (MBH98) was Northern Hemisphere, relied mainly on tree-rings, and went back about 600 years. Later reconstructions are multi-proxy, global and extend back as far as 2000 years.

The hockey stick is rather iconic in the climate debate, with some going so far as to claim that it’s been debunked (it hasn’t) and others suggesting all sorts of nefarious intent. Michael Mann, one of the authors of the original hockey stick paper, has written a nice article about what’s happened since publishing the first paper, and about the need to speak out.

Of course, our understanding of millenial temperatures has improved greatly. The reconstructions extend further back than they did originally. The analysis methods have improved, so we have more confidence in the results. We can use many different proxies to reconstruct these temperatures, so have better spatial and temporal resolution. This allows for an improved understanding of variability and of the role of both internal and external perturbations. However, the big picture has changed little. A warm period about 1000 years ago, typically referred to as the Medieval Warm Period, a general cooling towards what is referred to as the Little Ice Age, and then the modern warm period, that appears unprecedented in the last 1000 years, or so.

I think it’s important to realise that all of this is part of the normal scientific process. Early work will have limited data and will often use methods that have not been tried before. With time, we collect more data, develop improved methods, and – consequently – improve our understanding. We might even conclude that some of the early work used methods that we’d no longer regard as suitable. This doesn’t suddenly invalidate the earlier work, or imply kind of some nefarious intent. It seems pretty clear that the big picture presented by the early millenial temperature reconstructions have stood the test of time. I hope I, one day, have a paper that is still relevant, and being discussed, 20 years after being published.

Link:
I’ve always quite liked this post by David Appell that points out that the broad shape of millenial temperature reconstructions (hockey stick like) isn’t surprising.

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162 Responses to 20 years of hockey sticks

  1. The hockey stick paper is also an empirical study of natural variability. Two things the American culture warriors claim climatologists do not do, often on the same blog were they attack Michael Mann.

  2. Victor,
    Indeed, there are a lot of inconsistent arguments made on “skeptic” blogs. Arguing for the existence of a Medieval Warm Period while also arguing that climate sensitivity is low, for example.

  3. Also from David Appell, also from August 2015: 36 Hockey Sticks (And Counting)

  4. Thanks for the discussion. Your readers might be interested in two reviews of large-scale temperature reconstructions:

    Reconstructing Earth’s surface temperature over the past 2000 years: the science behind the headlines (2016) by Jason Smerdon and Henry Pollack, doi: 10.1002/wcc.418

    A noodle, hockey stick, and spaghetti plate: a perspective on high‐resolution paleoclimatology (2010) by David Frank, Jan Esper, Eduardo Zorita, and Rob Wilson, doi: 10.1002/wcc.53

    To quote from Smerdon and Pollack (2016): ‘It may indeed be time to abandon the hockey metaphor altogether, in favor of one that portrays the research evolution in this field as a collection of musicians in an orchestra who are warming up and tuning their instruments prior to a performance. The cacophonous mixture of sound during such moments comprises contributions from many instruments, each with their own tonal range of frequencies and each contributing to the collective sound in the chamber. As the musicians continue to warm up, however, the sound becomes more cohesive and instead of disharmony, the ensemble of instruments begins to coalesce around common meters and melodies. The continuing attempts to reconstruct and understand the climate of the [Common Era] are not unlike this orchestral analogy’

    cheers,
    Kevin

  5. As Tyndall was perhaps better aquainted with hurling than hockey , we may all have the wrong stick on the ice .

    The Irish model may provide the better metaphor, as it curves in three dimensions.

    https://vvattsupwiththat.blogspot.com/2018/04/keep-your-stick-on-ice.html

  6. angech says:

    “the hockey stick refers to millenial temperature reconstructions that look a bit like a hockey stick; a period of centuries during which temperatures appear reasonably flat, or cool slightly (the shaft), followed by a period of rapid cooling starting in the mid-1800s (the blade).”
    Think you mean period of rapid warming?
    If so change and delete my comment please.

    [Mod: Thanks, fixed.]

  7. Greg Wellman says:

    A rather major typo there … “a period of rapid cooling starting in the mid-1800s (the blade)”.
    That should of course be rapid warming. Or maybe I’m just trying to hide the decline 🙂

    [Mod: Thanks, fixed.]

  8. angech says:

    Played Hockey for years at high school age.
    Known as hacker for my enthusiasm if not my skill.
    Long shaft, short blade.
    “how controversial this topic can be.”
    If one puts recent thermometer temperature data on older thermometer data one gets a rise in the period 1850 to 1995 as M.Mann analyzed. Not that controversial.
    If one uses non thermometer proxies back in time one gets a flattish trend, not controversial.
    Join them together, voila, a hockey stick.
    What else would one expect?

  9. angech says:

    The reasons for a flat shaft,
    “PAGES2K
    “many proxy records spanning the last 2000 years are not annually resolved, and in some regions, most of the available records of any length lack annual resolution. The mean resolution of non-tree archives is 11 years, the median 1 year. For sedimentary archives the mean and median resolutions are 25 and 18 years, respectively.”
    are easy to see.
    Going back in time smooths and flattens the trend.
    Observations ten million years ago [as an example of the overall not the immediate problem] May have a change in temperature resolution of a thousand years. Observations a thousand years ago can have a resolution of 11 years. Annual data such as tree rings in some long lived species struggles to reach 600 years but provides a crucial overlap between thermometers and more esoteric proxies. At a cost of smoothing out changes.
    Hence the ability to see warming and cooling trends of up to 2 degrees over 100 years is lost as one goes back in time.
    Here is the conundrum. One did not even need to use tree ring proxies to get a flat shaft. It is a natural occurrence of using dating temperature proxies.
    But we have another proxy method of temperature reconstruction. History via written languages and history of agricultural practices and living styles by archeology. These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.
    The two results can coexist happily along side each other.

  10. Greg said: “Or maybe I’m just trying to hide the decline”

    Many people want to hide the decline of natural resources such as crude oil. The decline is why the USA is taking costly measures to frack the last remaining reservoirs and open up national monuments and parks in the remote possibility that there might be a little bit of crude oil remaining.

  11. Marco says:

    “If one uses non thermometer proxies back in time”

    If one is an ignoramus, this is the type of comments you write on a blog.

    A small hint, angech: the proxies of Mann went up to 1980.

    Another small hint: many newer reconstructions have proxies going even further towards the current year. Same result.

  12. angech,

    Going back in time smooths and flattens the trend.

    No, a great deal of work in the last 20 years has gone into improving the spatial and temporal resolution. As I understand it, we now have a pretty good understanding of temperature variability in the last millenium.

    Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.
    The two results can coexist happily along side each other.

    You’re going to have to provide some evidence for this, because I do not think this is correct. Remember that regional variability can be much bigger than global variability. That some regions have shown quite large temperature changes in the past, does not mean that, globally, there have been a number of times in the last 3000 years when there have been temperatures changes equivalent to the modern warming.

  13. verytallguy says:

    Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.

    No they don’t. Please provide a citation or withdraw the claim. Note that a single location does not constitute the globe.

  14. verytallguy says:

    Just out of idle curiosity, which bits were you motivated to rewrite?

  15. vtg,
    Second-to-last paragraph, mostly.

  16. angech says:

    Marco says:
    “If one uses non thermometer proxies back in time”
    “If one is an ignoramus, this is the type of comments you write on a blog.” [these are?]
    Sorry to offend, the meaning , that one has to use proxies for temperatures as thermometers were none existent seemed clear.
    “A small hint, angech: the proxies of Mann went up to 1980.”
    Longer than that Marco.
    He did not use the data after 1980 yet the study went to 1995.

  17. angech says:

    “Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.
    You’re going to have to provide some evidence for this, because I do not think this is correct.”
    I might ask over at SOD or Lucia’s for help
    I feel confident in the statement but as others observe my confidence is not proof. I would be happy if someone like Dave or BBD were to take up the cudgel on my behalf? Though it is a thankless task.

  18. Dave_Geologist says:

    Why controversial ATTP? Surely only in the sense that evolution is controversial to creationists, and the round earth is to flat-earthers.

  19. angech,
    I may be wrong, but I don’t think the proxies go all the way to 1995.

    Dave,
    It’s just a topic that seems to invite controversy, even if that isn’t the intent.

  20. angech “I feel confident in the statement but as others observe my confidence is not proof”

    Nobody is asking for proof, just evidence. There is a technical term for confidently making assertions of fact without evidence.

  21. verytallguy says:

    I feel confident in the statement

    You can’t provide any evidence for a statement, yet you feel confident in it?

    *Why* do you feel so confident?

  22. It’s my understanding that you couldn’t even hide modern warming events in the Marcott et al. reconstructions, so I don’t see how we can be missing many of these in the higher-resolution millenial reconstructions.

  23. Only yesterday, angech wrote:

    What gets me is that nearly every one here has the brain power, education,ability and desire to discuss most issues in an agreeable way.
    Yet when we come to a true disagreement basic win at all costs thinking comes into play.

    For instance making claims without knowing whether they are supported by evidence so that your “opponent” then wastes time and energy doing your fact checking for you? Doing that sort of thing makes it pretty clear that someone does not have the desire to discuss this issue in an “agreeable way”. Personally I find that kind of approach to debate rather offensive (as it shows no respect either for the truth or your “opponent”).

  24. A most interesting set of proxies are the coral proxies of the equatorial Pacific. They have the important characteristic of an excellent correlation with modern-day temperature indices of that region — where the modern instrumental record overlaps with the proxy record the correlation coefficient is upwards of 0.7-0.8, so the calibration back in time to hundreds of years before the modern era is assumed to be valid.

    https://www.clim-past.net/6/1/2010/cp-6-1-2010.pdf

    But since the temperature indices that correlate the best are Nino34, not much of a hockey stick is observed. This is not surprising because most of the variation in Nino34 is just ENSO variations, and ENSO variations are understood to be largely immune from the global warming trend, likely having more to do with the stationary cyclic tidal mixing forces that Munk and Wunsch pointed out years ago.

  25. MarkB says:

    [i]angech: Here is the conundrum. One did not even need to use tree ring proxies to get a flat shaft. It is a natural occurrence of using dating temperature proxies.[/i]
    Tree rings are an annual proxy which is precisely why they are important in this sort of thing. Your statement seems to be “If you don’t those proxies with annual resolution, you don’t get annual resolution”. Which isn’t a very productive statement if one’s objective is clarity on the matter.

  26. Dave_Geologist says:

    angech

    Going back in time smooths and flattens the trend.

    Not inherently so. Depends on the proxy. Tree-rings, for example, can be annual as the analysis cost per year is not huge. Speleothems from places with seasonal rainfall generally have annual growth rings like trees. They could in principle be measured annually, and sometimes are, but more often less frequently. Presumably cost is a factor as each sample needs a mass spectrometer run. Perhaps someone with lots of money and an interest in the subject could sponsor a study with annual resolution for thousands of years. The Koch Foundation, for example. Wonder why they haven’t? A 1°C rise over 30-50 years during the MWP, missed by mainstream science, would be a real feather in their cap.

    The speleothem data can be downloaded here. The dataset contains a link to an explanatory paper. Other datasets are on the same site. The median age spacing for that speleothem data is 8 years (you’d have to read the source papers to confirm whether they sampled not-every-year from an annually resolved series, or interpolated data from a series without annual rings). There are more than 27,000 data points from 60 series, so I’d be surprised if there’s a 30-50 year period in the last few thousand years that’s been left fortuitously unsampled. In fact, bearing in mind that is just one proxy out of many, the operative word would be astonished, not surprised. Yes you could probably lose 5 years of warming, but 5 years of warming doesn’t cut it as a past analogue to today’s 50 years. And yes they’re annual measures of some sort, but that’s why they’re compared with or tied onto annual-average surface temperatures. And of course you can filter the modern thermometer data to have the same bandwidth as the proxies. Know what, I’ll bet someone’s done that already!

    Remember to avoid the common blog pitfalls if you do your own plotting.
    1) Don’t assume present in B.P. means today or the date of the paper or the age of the last sample. It’s generally radiocarbon B.P., where 1950 is year zero.
    2) Many of the proxies end in the late 20th century. So don’t forget to add on the thermometer record. The point of the proxies is to extend the thermometer record back in time, not to validate the thermometer record. If the MWP was 0.2°C warmer than 1980 or whatever, that doesn’t prove the MWP was warmer than today, because today is a lot warmer than 1980.

  27. Dave_Geologist says:

    Paul

    But since the temperature indices that correlate the best are Nino34, not much of a hockey stick is observed.

    Well, yes. That’s why the title of the paper is “A unified proxy for ENSO and PDO variability since 1650”. The original proxies had been analysed in a way that aimed to exclude “local climatic and other large scale variability uncorrelated to ENSO”. IOW to remove, among other things, the hockey stick. So no-hockey-stick in the reanalysis is not exactly uprising.

  28. Willard says:

    > I might ask over at SOD or Lucia’s for help[.] I feel confident in the statement

    Another data point for the need to distinguish confidence and self-efficacy.

  29. Dave, PDO is in fact a large scale variability and that is in the title of the paper.

    My point is I don’t understand why the calibration between coral proxy and instrument isn’t paraded around more often as it is very impressive.

    I think that one way the coral proxy variation is manifested is by changes in the sea-level, so if the sea-level goes down temporarily as per an El Nino (or La Nina) episode, the coral gets exposed to air and does not grow as fast as it would be if completely underwater. I don’t recall seeing this anywhere as an explanation.

  30. BBD says:

    Perhaps someone with lots of money and an interest in the subject could sponsor a study with annual resolution for thousands of years. The Koch Foundation, for example. Wonder why they haven’t? A 1°C rise over 30-50 years during the MWP, missed by mainstream science, would be a real feather in their cap.

    Quite. But perhaps the Brothers Koch lost their enthusiasm for funding science after the BEST debacle.

    @angech

    As usual, others have already explained how and why your unsubstantiated claims are (as usual) incorrect. So do us all a favour and don’t double-down on them.

  31. Since the re-written post here no longer contains my tweet or the plot of temperature reconstructions, you can find it here: https://twitter.com/thirstygecko/status/987337384839675905

    My point in posting the plot was that we’ve actually learned quite a bit over the intervening 20 years about our proxies, their strengths and weaknesses, the importance or impact of methodological choices, and about the nature and magnitude of forced and internal climate system variability.

    If you care about Common Era temperature reconstructions only in the context of the Hockey Stick as icon, maybe you don’t care about any of this. If one actually cares about what these reconstructions tell us about how the climate system works and what that implies for the future, the progress in this field matters quite a bit.

    cheers,
    Kevin

  32. verytallguy says:

    …what these reconstructions tell us about how the climate system works and what that implies for the future…

    Would you care to summarise your views on these topics (or provide a link)?

    thank you

  33. Kevin,
    Thanks.

    If one actually cares about what these reconstructions tell us about how the climate system works and what that implies for the future, the progress in this field matters quite a bit.

    Of course, this is important and matters a lot (I certainly was never intending to imply otherwise). I’ve had a look through some of the papers you suggested. Admittedly, I haven’t read them in extensive detail (trying to prepare a talk I’m giving this week, and write a paper, so slightly snowed under). My impression was that they were mostly discussing how to improve proxy reconstructions and why these are important. Is there some basic highlight about the nature and magnitude of the forced response and internal variability that has been obtained from these reconstructions? Is there something that would be useful to know when thinking about what these reconstructions tell us about how the climate system works?

  34. To quote Smerdon and Pollack 2016, again: ‘These differences [between Common Era temperature reconstruction] have driven an evolving understanding about the importance of developing proxies in under-sampled regions, the spectral fidelity of proxy records, the statistical methods and uncertainties of climate reconstruction techniques, the similarities and differences between reconstructed and modeled estimates of CE climate, and the dynamics of forced and internal climate variability.’

    Just 2 examples:

    1. The response of the climate system to volcanic eruptions. A considerably body of literature now suggests that climate model simulations of the Northern Hemisphere summer temperature response to these events are too cold compared to proxies. This model-proxy difference persists even in the latest reconstructions which use mostly tree-ring latewood density data. This finding has motivated useful collaborations (http://pastglobalchanges.org/ini/wg/vics/intro) to understand the origin of the differences from both the proxy and model side of the field (my own work suggests this is linked to how volcanic eruptions are represented in the models, as opposed to – for instance – anything having to do with model climate sensitivity).

    2. Centennial-scale variability. As the field of large-scale temperature reconstructions have progressed, we’ve become aware of the methodological and data challenges in full characterizing low frequency variability (centennial to millennial time scales) and taken steps to retain and recover more of the low frequency signal. Indeed, this was first broadly recognized as early as the Esper, Cook, Schweingruber paper in 2002 (http://science.sciencemag.org/content/295/5563/2250.full). What forcings are linked to this low frequency variability and what does it reveal about the climate system sensitivity to these forcings? How large were these forcings? And do we capture these in climate model simulations?

    In both these cases, understanding how changes in forcing translate into changes in temperature (large-scale or regional) requires reconstructions which capture the full spectrum of the response of the system to that forcing. Improved reconstructions also allow us to characterize the range of natural variability and how it changes in response to changes in the mean state.

  35. And, if I may quote myself here (https://www.sciencedirect.com/science/article/pii/S0277379117301592):

    ‘Paleoclimate reconstructions of past temperature extend knowledge of climate system variability beyond that available from the limited instrumental observational record. They offer longer timescales over which to observe a more complete range of variability in solar and volcanic forcing, extended opportunities to characterize internal climate system fluctuations at decadal and longer timescales, and the potential to separate forced and un-forced responses to better understand their magnitude and spatiotemporal patterns’

  36. Kevin,
    Thanks, I had seen that bit about volcanoes. Am I right in thinking that we still don’t really understand if the centennial-scale variability is externally, or internally, forced?

  37. Regarding the centennial-scale forcing: The PAGES2k-PMIP group has a paper in Climate of the Past comparing last millennium models and the continental-scale reconstructions:

    https://www.clim-past.net/11/1673/2015/

    A few points:
    1. Models and reconstructions match at high northern and midlatitudes, probably because of the strongly forced signal.
    2. ‘Simulations are more regionally coherent than the reconstructions, perhaps due to an underestimation of the magnitude of internal variability in models or to an overestimation of the response to the external forcing in the Southern Hemisphere’

    In another PAGES2k paper, Helen McGregor et al. showed that the long-term cooling over the Common Era (until the modern warming) could be driven by volcanic cooling (particularly during the Little Ice Age) as opposed to orbital forcing: https://www.nature.com/articles/ngeo2510

    So, I think this is actually a fast-moving front – the existence of Last Millennium single-forced ensembles is opening up new avenues of analysis for understanding these low frequency patterns, as are newer proxy reconstructions. I think one really large question mark is still the Southern Hemisphere, which from the more limited proxy data and reconstructions look different than the modeled forced response.

    cheers,
    Kevin

  38. Are the two McGregor’s working on ocean proxies related?
    S.McGregor lead author for the UEP proxy and Helen McGregor lead author for the PAGES2K

    I think it’s worthwhile to discuss exactly how UEP type coral proxy analysis can discriminate the natural variability from the long-term trends. I had a long discussion with a presenter at last December’s AGU on this topic. He claimed lots of the long-term variation seen in coral proxies over the last 1000 years disappears when composed properly. In other words, it’s very flat.

  39. Dave_Geologist says:

    Paul
    “local climatic and other large scale variability uncorrelated to ENSO” is a quote from the paper. Since “the UEP (Unified ENSO Proxy) displays multi-decadal variability that is consistent with the 20th century variability of the PDO and IPO” (see Fig. 10), it would seem that whatever large scale variabilities the original proxies were aiming to filter out, the PDO wasn’t one of them. Or that they failed. On first reading I took it as large timescale, but it could be large geographical scale.

    I would have thought they’d avoid taking samples shallow enough to have been sub-aerially exposed, at least during growth. You don’t want rainwater influence as it has a different isotope ratio to seawater. Why trumpet corals? The scientists know that the proxies are models, all wrong but some useful, and how to recognise the useful ones and to know when and where they’re useful. If it’s to swing doubters into line, I doubt very much if it will work. Anyone who denies the existing mountain of evidence isn’t going to be persuaded by a graph with a high correlation coefficient. And corals are restricted to tropical oceans for this purpose. There are deep-water, extratropical corals, and some have been used as proxies for deep-water current changes, but they’re no good for estimating SSTs.

  40. Dave,
    This is what they say:
    “Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary”

    ENSO is a significant factor in global temperature variations, and if the coral proxies reflect ENSO, there is nothing wrong with that.

    This is the research that says that the amount of low-frequency variation (multidecadal and above) in the coral proxy data is minimal:
    http://adsabs.harvard.edu/abs/2017AGUFMPP31A1245L

    “Reconstructing the spectrum of Pacific SST variability has proven to be difficult both because of complications with proxy systems such as tree rings and the relatively small number of records from the tropical Pacific. Wae show that the small number of long coral δ18O and Sr/Ca records has caused a bias towards having too much low-frequency variability in PCR, CPS, and RegEM reconstructions of Pacific variability. “

  41. Kevin,
    Thanks, that’s interesting.

  42. Paul,

    In case you’re interested, we (Tierney et al. 2015) identified low frequency spectral mismatches between observations and reconstructions of eastern tropical Pacific sea surface temperatures in this paper a few years ago: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014PA002717

    As we wrote then: ‘Comparison in the frequency domain between our reconstructions and observational SSTs over the time span of the observational period (1870 to present) demonstrates that our reconstructions capture the spectral characteristics of modern tropical ocean SST variability in our Indian, western Pacific, and Atlantic regions, including interannual spectral peaks associated with ENSO and multidecadal power associated with the AMO (Figure 6). The exception is the presence of low-frequency power in our eastern Pacific reconstruction, which we believe is a reflection of a spurious reconstructed warming trend …’

    The spurious low frequency component of the eastern tropical Pacific reconstruction we refer to is likely linked to the influence of the ocean water oxygen isotope composition itself, probably reflecting salinity, that at least for a time in the late 20th century doesn’t covary with temperature trends in the eastern tropical Pacific.

    cheers,
    Kevin

  43. Michael Hauber says:

    To me the hockey stick seems a great territory for deniers to debate in. At my level of exerptise, and with my level of motivation, I was never able to truly get to the bottom of Mann vs Mcyntire, although I trust Mann much more and consider he is likely to be correct. But when I go into the argument, counter, counter the counter etc cycle I end up getting lost and confused.

    In comparison on a topic like modern temps, some of the detailed arguments about UHI, and specific adjustment policiues in GIS can get confusing. But it is easy to take a step back from these confusing arguments, look at temp calculations that ignore all adjustments and show much the same thing, or look at the multiple lines of evidence from nature such as cryosphere, and changed flowering/migration times and be very confident that the world has warmed up in the last century.

    The fact is that the hockey stick is not particularly important for the scientific case for climate change case. It does make good propoganda, but in reality the world was warmer than it is now and how much does it really matter whether that was 500 years ago or 10 million? But if deniers throw up arguments that paleo experts consider nonsense they will of course be obliged to defend their work and reputation and so a difficult for non experts to follow argument results, and the appearance of controversy and not certainty is created..

  44. angech says:

    Climate field reconstruction (CFR) methods; MBH 1998 and 1999
    “The NRC committee stated that “The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that
    includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators”. It said “Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium”, though there were substantial uncertainties before about 1600″”.

    “It added that “Even less confidence can be placed in the original conclusions by Mann et al. (1999) that ‘the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium’ because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods and because not all of the available proxies record temperature information on such short timescales.”

    It noted that “Surface temperature reconstructions for periods prior to the industrial era are only one of multiple lines of evidence supporting the conclusion that climatic warming is occurring in response to human activities, and they are not the primary evidence.”

    “At the press conference, North said of the MBH papers that “we do roughly agree with the substance of their findings. There is a small disagreement over exactly how sure we are.”[9] All three from the NRC committee panel said it was probable, though not certain, that current warming exceeded any previous peak in the last thousand years.[3] When asked if they could quantify “less confidence” and “plausible”, Bloomfield explained that their wording reflected the panel’s scientific judgements rather than well defined statistical procedures, and “When we speak of ‘less confidence’ we’re more into a level of sort of 2 to 1 odds, which IPCC, they interpreted ‘likely’ as that level, roughly 2 to 1 odds or better.The IPCC 2001 report had been careful to give the two-year-old paper’s conclusion fairly low confidence as “likely” at 2 to 1 odds, ”

    MBH99 and controversy
    The NRC Chapter 11 of the report described MBH98 as the “first systematic, statistically based synthesis of multiple climate proxies”, and noted that the MBH reconstructions “were the first to include explicit statistical error bars”.[14] The report’s overview section said that, despite the wide error bars, the hockey stick graph “was misinterpreted by some as indicating the existence of one ‘definitive’ reconstruction with small century-to-century variability prior to the mid-19th century”.

    When questioned about who had said MBH99 was definitive when the paper itself emphasised the uncertainties, North said his opinion was that, “The community probably took the results to be more definitive than Mann and colleagues originally intended.”

    This basically agrees and supports what I have said. There are possible higher and lower spikes in the temperatures in the past that do not show because of “the wide error bars” as one goes backwards and the “uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods’.

  45. Harry Twinotter says:

    Michael Hauber.

    “but in reality the world was warmer than it is now and how much does it really matter whether that was 500 years ago or 10 million?”

    It matters a great deal. The global mean temperature for the last several thousand years sets the climate sensitivity baseline for the concentration of CO2 at the time. Also it serves as a means of falsifying the CO2 global warming hypothesis; if global warming occurred during this time while CO2 remained steady, then you would have to conclude factors other than CO2 could be responsible.

  46. angech,

    This basically agrees and supports what I have said. There are possible higher and lower spikes in the temperatures in the past that do not show because of “the wide error bars” as one goes backwards and the “uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods’.

    That the uncertainties in the early reconstructions are large does not imply that there were periods comparable to our modern warming that we just can’t see. Not only have the reconstructions improved, but if there were large perturbations that lasted ~200 years, then I think some evidence of these would be seen even in the early reconstructions.

  47. Kevin, Yes, Loope said these low-frequency variations were spurious too, mainly from stitching together separate intervals. Didn’t realize the previous work that was done.

  48. Dave_Geologist says:

    angech
    I can’t prove the non-existence of unicorns. And neither can Mann or NRC prove that there wasn’t a warmer year than 1998 in the past. All they can do is quote various levels of confidence, with uncertainty bounds (which as you quote were present in MBH99). Hence “There is a small disagreement over exactly how sure we are.” It will always be possible we missed something, although remember, we’re currently experiencing not just local high temperatures but a global average temperature rise. Finding one or two or six spikes at one or two or six different times in the last two thousand years does not past global warming make. They have to be widely distributed and synchronous, at least within 30-50 years. Otherwise no cigar.

    And while some of the proxies are inherently smeared over multiple years, others are single-year samples but not every year. Yes, some are more strongly influenced by summer or winter than annual average. But because summer, winter and annual average temperatures are all going up today, if you’re looking for a natural analogue in the past that shouldn’t matter within each time series. I see it as like a medical meta-analysis where the more trials you add and/or the bigger the trials, the more a real effect rises out of the noise and a spurious effect sinks back into the noise. What are the chances that not only MBH99 missed that past glorious spike, but all the others too? Ultimately you reach a point where credulity is strained. And of course if you say “but the 5% upper bound” you’re rejecting 100% evidence today on the basis that there’s a 5% chance something in the past might challenge it.

    And even if you find a suitable series, if you searched through a hundred others to find one which does get its median above 1998, you need to do a Bonferroni correction for the multiple-testing problem. So you should be requiring 99.95% confidence from that series, not 95%.

    And finally, it’s not 1998 any more. 1998 just scrapes into the top ten hottest years, and is sure to fall out with the next El Nino if not before. If the NRC was reporting today, I’ll bet they’d have had much higher confidence.

  49. BBD says:

    Ultimately you reach a point where credulity is strained.

    Not to mention patience.

  50. Chubbs says:

    “Some mosses in the eastern Canadian Arctic, long entombed in ice, are now emerging into the sunlight. And the radiocarbon ages of those plants suggest that summertime temperatures in the region are the warmest they’ve been in tens of thousands of years. ”

    https://www.sciencenews.org/article/ice-retreats-frozen-mosses-emerge-tell-climate-change-tale?tgt=nr&utm_content=62269357&utm_medium=social&utm_source=twitter

  51. metzomagic says:

    I see angech has picked up on Steve McIntyre’s old saw from the time Marcott et. al. 2013 was published. It basically goes like this: if the temporal resolution of the proxies going far back in time was only x years (say x = 200), then what’s to say there couldn’t have been a 1 deg C spike in temperatures like we have today, but it arose and dissipated so quickly that all the proxies missed it?

    As with all things regarding McIntyre, the statistics may be valid but he never seems to be able to provide a physical basis to back up the statistics. What physical process could possibly produce a 1 deg C spike in temperatures that disappeared without a trace within a 200 year time span? *crickets*

  52. zebra says:

    Michael Hauber and metzomagic make very good points.

    MH:

    But if deniers throw up arguments that paleo experts consider nonsense they will of course be obliged to defend their work and reputation and so a difficult for non experts to follow argument results, and the appearance of controversy and not certainty is created..

    Yes, that’s the idea– when Dave responds to angech with fancy statistical stuff, I say: “Whoa, Dave is way better at that than I am”. But, 99% of the population says: “Whoa, angech is just as good at that as Dave.”

    And of course, it reinforces the idea that the statistics precede the physics, when, as metzo implies, it should be the other way around.

    Related @Harry Twinotter

    Also it serves as a means of falsifying the CO2 global warming hypothesis; if global warming occurred during this time while CO2 remained steady, then you would have to conclude factors other than CO2 could be responsible.

    Responsible for the current warming? No, not at all.

  53. angech says:

    Thanks Metzomagic, as a relative newcomer to these issues, maybe 6 years if lucky, I missed the MM controversy and came in just after the fuss with Macintyre. Whereas a lot of commentators here are probably 10 years plus into the issues.
    Most people seem to miss that I agreed that a hockey stick is seen. The controversy is not that one would get a hockey stick with whatever method one uses but what it all means.
    Pointing out that it would occur with or without CO2 is the issue.
    If CO2 induced one would expected a continued rise and a steeper rise than what has occurred. Time will tell.
    As for 200 people on a blog trying to change the world, who knows,but both sides are definitely to be congratulated for trying.

  54. “Yes, that’s the idea– when Dave responds to angech with fancy statistical stuff, I say: “Whoa, Dave is way better at that than I am”. But, 99% of the population says: “Whoa, angech is just as good at that as Dave.”

    And of course, it reinforces the idea that the statistics precede the physics, when, as metzo implies, it should be the other way around. ”

    angech wasn’t mentioning physics any more than Dave did, so I don’t see how that conclusion can be drawn.

    Even angech’s own sources refute him. His original claim was:

    These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.

    [emphasis mine]

    and he supports that with:

    “The NRC committee stated that “The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that
    includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators”

    and says:

    This basically agrees and supports what I have said. There are possible higher and lower spikes in the temperatures in the past that do not show because of “the wide error bars” as one goes backwards and the “uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods’.

    Err, no it doesn’t, it says that the recent warming is unprecedented. Note also the goal-post shift from “have happened” to such spikes being “possible”, without acknowledging the weakening of his position. Rather shabby.

  55. Willard says:

    > 99% of the population says: […]

    Citation needed.

  56. angech,

    The controversy is not that one would get a hockey stick with whatever method one uses but what it all means.
    Pointing out that it would occur with or without CO2 is the issue.

    A hockey-stick like shape is roughly what we would broadly expect if we have had a period with relative small changes in external forcing, followed by a recent period during which it has increased quite a lot (through our emission of CO2 into the atmosphere). If you could show that we could get a hockey stick like shape without something like this, that would be quite impressive. I don’t really think that you can.

  57. Paul,

    Not sure I follow your (or Loope and Overpeck’s) argument here. We know where the 20th century spectral differences come from and it isn’t from ‘stitching together’ records. Guess we’ll have to see when and if they publish their results.

    cheers,
    Kevin

  58. angech writes

    “If CO2 induced one would expected a continued rise and a steeper rise than what has occurred.”

    yet again angech makes an assertion with no evidence. Please explain exactly how steep the rise should be, provide supporting references.

  59. Kevin,
    Just so you know, Paul has a tendency to promote things that may support his theory (that he promotes regularly on blogs) about ENSO events. I don’t really follow it myself.

  60. Kevin said:

    “Not sure I follow your (or Loope and Overpeck’s) argument here. We know where the 20th century spectral differences come from and it isn’t from ‘stitching together’ records. Guess we’ll have to see when and if they publish their results.”

    I spent a half-hour talking to Loope at the AGU at his poster session. From what I understand he was piecing together for example 20-100-year records from different corals to create a several hundred year record. He claimed that there were many spectral boundary effects from the short-term records that disappeared when the records were pulled together. Calling it “stitching” may not be the correct term but that’s the way that I interpreted it.

  61. Dave_Geologist says:

    angech

    If CO2 induced one would expected a continued rise and a steeper rise than what has occurred.

    You mean like the current continued rise? The one that’s relegated the record El Noni of 1998 to the ninth hottest year. That rise? And nope, you’re so 2008. The current trend is slap-bang in the middle of the IPCC range for the emissions path closest to historical reality.

    Time will tell

    Already has. It’s real, it’s CO2 and it’s ours.

  62. BBD says:

    If CO2 induced one would expected a continued rise and a steeper rise than what has occurred.

    Why?

  63. The Very Reverend Jebediah Hypotenuse says:


    It’s real, it’s CO2 and it’s ours.

    Indeed.
    And anyone who was paying sufficient attention knew that in the 1980s.
    Before there were any blogs.

  64. Dave_Geologist says:

    Paul,

    Yes, Loope said these low-frequency variations were spurious too, mainly from stitching together separate intervals.

    and

    He claimed that there were many spectral boundary effects from the short-term records that disappeared when the records were pulled together

    contradict each other. The second one makes more sense. Individual short records will suffer from edge effects, particularly at low frequencies/long periods. By stitching them together, presumably with some sort of shift-and-scale so there’s not a step at the join, you can eliminate those effects and reliably extract longer periods.

    It’s a common problem, also impacting curvature analysis in structural geology (although workarounds have been proposed such as repeating or mirroring the input data), and, bizarrely, periods (the other kind). McLintock’s study on female dorm occupants unconsciously synchronising their periods has, sadly for the world of internet memes, been re-analysed and shown not to be statistically significant. She was aware of the edge effect problem, as presumably were her supervisor and the peer reviewers, but the difference looked big enough that they thought it was probably still significant. Their problem was that for the particular dataset she had there is no analytical significance test available. There is for two subjects or for an infinite number of subjects, but not for numbers in between. IIRC she tested the two end-members but there was a factor of two between their test criteria and her result fell about half-way between. So perhaps it would have been better to say “maybe significant”, but we don’t have the tools to tell for sure. Decades later we do have the tools (Monte Carlo Simulation) and someone reconstructed the dataset and ran a bunch of trials with random input data and the right number of subjects in order to determine the correct test statistic for her study*. Sadly for the internet meme, it failed the test.

    *Women Do Not Synchronize Their Menstrual Cycles, Yan & Schank 2006..

  65. Dave said:

    “contradict each other”

    Loope said others in the past were improperly “stitching” them together and he was doing it correctly. Sorry for the confusion on this. He had several examples in his poster where you could see spectral peaks from the piece-wise collection of the samples. And then he showed a flat spectrum when his team “stitched” them together properly.

    Maybe it’s a moot point anyways because Kevin said he did this work earlier
    https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014PA002717

    And I will have to wait for Loope’s pape to study the details.

    The work in general suggests that the variation is less than previously thought.

  66. Dave_Geologist says:

    Paul, got it now.
    As per my “shift-and-scale” comment. Merging with edge effects left in will increase the power of the analysis at short periods, but retain artifacts at long periods.
    Not necessarily moot. One of the beauties of natural observational data, vs. controlled experiments, is that you can repeat the same analysis with different datasets, and potentially learn something new each time 😉 .

  67. Mal Adapted says:

    angech:

    What gets me is that nearly every one here has the brain power, education,ability and desire to discuss most issues in an agreeable way.

    You rebunk a lot of repeatedly-debunked AGW-denier nonsense here, usually with an agreeable tone. Yet your data are frequently false, and your logic, fallacious. Do you consider that an appropriate use of your brain power, education and ability? It may not be ‘disagreeable’, but it’s not respectable either. Whence comes your desire to keep doing it?

    Furthermore: regardless of the truth or falsehood of your factual claims, do you truly not recognize the requirement to document any that aren’t ‘settled science’? The title of the OP should make it clear that hockey-stick paleoclimatological profiles are settled science. Remember that extraordinary claims, like you’re making here about them, require extraordinary evidence.

    If you’re not sure what evidence to trust, you’re referred again to John Nielsen-Gammon’s call at the 2012 AGU meeting for more emphasis on scientific meta-literacy in the public schools:

    [“Storms like Sandy will become more frequent because of climate change.”]

    There are, perhaps, less than a thousand people worldwide who know enough about climate change’s impacts on tropical cyclones, extratropical transitions, wind speeds, rainfall rates, and sea level rise to qualify them to evaluate that statement. It’s not even clear that I’m [JNG] one of them! The requisite level of climate literacy is enormous.

    But there’s an important lesson here about how we decide which scientific statements to believe and which ones not to believe. Those of us who are trained scientists but who do not have enough personal literacy to independently evaluate a particular statement do not throw up our hands in despair. Instead, we evaluate the source and the context.

    We scientists rely upon a hierarchy of reliability. We know that a talking head is less reliable than a press release. We know that a press release is less reliable than a paper. We know that an ordinary peer-reviewed paper is less reliable than a review article. And so on, all the way up to a National Academy report. If we’re equipped with knowledge of this hierarchy of reliability, we can generally do a good job navigating through an unfamiliar field, even if we have very little prior technical knowledge in that field.

    One more time IMIMO: if you’re a genuine skeptic and aren’t expert on a topic, you’ll acknowledge there may nonetheless be genuine experts who, collectively at least, know more than you do about it. Your challenge is to distinguish genuine from fake experts. If they’re authors of a National Academy report, they’re genuine experts. If all you know is that their name is on a peer-reviewed paper published in some ostensibly scientific venue, then they may or may not be experts. If they’ve got strong credentials but make claims that contradict the lopsided consensus of their peers, they’re probably not as expert as they think they are. If they’re just random guys with blogs, or commenters on those blogs, they’re no more expert than you or me!

  68. izen says:

    @-metzomagic
    “What physical process could possibly produce a 1 deg C spike in temperatures that disappeared without a trace within a 200 year time span?”

    It is a good question.
    A short global warming of similar magnitude to the present would need a large-scale cause.
    Solar variation is excluded because it would alter Carbon and Beryllium isotope ratios and be obvious in the radiocarbon dating curve. I suspect a large methane ‘burp’ would also shift the carbon ratios sufficiently to be detectable.
    Albedo changes sufficient to cause that much warming are only possible from massive global ice cover loss, that would show up in global glacier and ice-cap cores.
    I am unable to think of any other causes of aquiring the extra energy in less than a century that would not show up as a macroscopic effect.

    But apart from the abscence of a possible cause, there is also a lack of inevitable effects.
    We know what effects the current rapid warming has had. It is inevitable that any similar energy gain in the past would have the same effect. AFAIK there is no evidence that there was a similar sea level rise in the Holocene since the end of the de-glaciation. I suspect if there was it would show up in the timing and observable locations of solar and lunar eclipses.

    Otzi the ice man would have defrosted in any previous rapid warming as glacier mass balance shrinks. There is a lot of other evidence that glaciers have not been this small for ~10,000 years. Most glaciers, especialy the S American glaciers that have recently melted out would have done so previously and would start from that event, or have a massive gap in the holocene cores.
    A past spike would also have effects on plant and animal distribution as it is now. Tree lines on moutains and the position of the circumpolar forest should have shifted as they are doing now.evidence for that is absent. As is any change in plant and animal home ranges.

    While the proxies may theoretically be able to miss a short spike in the Holocene, there are other reasons to doubt it could happen and not be evident.
    Perhaps this quote expresses the problem best.
    Gregory (Scotland Yard detective): “Is there any other point to which you would wish to draw my attention?”
    Holmes: “To the curious incident of the dog in the night-time.”
    Gregory: “The dog did nothing in the night-time.”
    Holmes: “That was the curious incident.

  69. angech says:

    dikranmarsupial says: April 24, 2018
    “Even angech’s own sources refute him. His original claim was:
    These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years. [emphasis mine]
    and he supports that with:
    “The NRC committee stated that “The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that
    includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators”
    and says: This basically agrees and supports what I have said. There are possible higher and lower spikes in the temperatures in the past that do not show because of “the wide error bars” as one goes backwards and the “uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods’.

    DM “Err, no it doesn’t, it says that the recent warming is unprecedented.”

    Having been called out in the past for not fully quoting comments I guess I can do a tu quoque?
    The NRC did not say “the recent warming is unprecedented.” Mann et al said that.
    The part that DM leaves out says clearly, plausible only, with substantial uncertainties before 1600. I will append the bit he missed by accident.

    “Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium”, though there were substantial uncertainties before about 1600″”.

    “Note also the goal-post shift from “have happened” to such spikes being “possible”, without acknowledging the weakening of his position. Rather shabby.”

    Sorry DM I have not changed my position. No goal post shift. Read my comment again noting “have happened” refers to events ” past temperatures, but only locally” which are well known and real.
    The ”spikes” being possible refers to the separate concept that such temperature spikes may have been general rather than local and would not be visible due to the large error range in time and temperature.
    Good try.

  70. angech says:

    Mal Adapted
    “You rebunk a lot of repeatedly-debunked AGW-denier nonsense here, usually with an agreeable tone. Yet your data are frequently false, and your logic, fallacious”
    “The title of the OP should make it clear that hockey-stick paleoclimatological profiles are settled science”
    I agree the profiles are settled. I point out that the ways we have of measuring lead to a flat stem.
    I point out, as MM et al did, that there are uncertainties that worsen as we go back in time.I make the observation that a rise [or fall] in temperature over 150 years of the same magnitude is possible in the past 1000-3000 years within the error bars and without being able to be shown up due to the statistical nature of the proxies as we go further back in time beyond the scope of most tree ring studies.
    That is all. Use it as you will.

  71. Here is paper discussing a recent long 500-year proxy record
    “Autumn–winter minimum temperature changes in the southern Sikhote-Alin mountain range of northeastern Asia since 1529 AD” https://www.clim-past.net/14/57/2018/

    What I find odd about the discussion in the paper is that not once is the strong biennial oscillation noted in the power spectrum. This is right on the Nyquist sampling limit for annual sampling, but that should not be an issue. Yet, many other weaker signals are identified.

  72. angech,
    You keep claiming this, but I don’t think it is correct. I think the proxies have a good enough resolution for us to see if there previous periods with warming comparable to the modern warming. There is little evidence to suggest that there has been.

  73. Marco says:

    “Possible” is not necessarily the same as “plausible”. It should in principle be possible *and* plausible to create a completely artificial simulation of past climate that includes some kind of ‘spike’ in temperature of a certain duration and height, and then apply a random sampling with gaps of a certain length, add some realistic noise on the measurement, and then determine how likely it is that we’d miss that spike. I don’t have the expertise to do such a simulation, but an interested person is free to take my idea and try it out. It is certainly plausible that there is a journal interested in such a simulation, and it is plausible that a similar simulation has been done before in a different field – I can at least imagine that there are times people would ask themselves the question what their sampling frequency would have to be to determine an increase or decrease in signal of x duration and y height (and the relationship between the two).

    On a side-note regarding possibility and plausibility, I remember the paper by Ernst-Georg Beck on CO2 concentration variability in modern times (last 180 years, see http://journals.sagepub.com/doi/abs/10.1260/095830507780682147), where a comment (by Ralph Keeling, I think) pointed out that assuming this CO2 variability over the last 180 years as representative of atmospheric levels of CO2 lacks a credible mechanism, as it would involve enormous carbon fluxes within a few years to achieve the 120 ppm increase in the five years up to WW2, and the same level of decrease just after WW2. And, of course, it would require an explanation as to why this enormous variability suddenly magically stopped when IR measurements were introduced in places without significant impact of photosynthesis and human activity.

  74. BBD says:

    I point out, as MM et al did, that there are uncertainties that worsen as we go back in time.I make the observation that a rise [or fall] in temperature over 150 years of the same magnitude is possible in the past 1000-3000 years

    I dispute this. Please describe a plausible physical mechanism capable of producing a ~1C spike in GAT lasting ~150 years.

    Also, why no analog of modern SLR from thermal expansion?

    After Kopp et al. (2016) <a href="http://www.climatecentral.org/news/study-reveals-acceleration-of-sea-level-rise-20055&quot;Source: Climatecentral.

  75. Mal, wrote ” It may not be ‘disagreeable’, but it’s not respectable either. Whence comes your desire to keep doing it?”

    having seen plenty of angech’s posts on climate skeptic blogs, it seems pretty clear to me that he is not engaging in good-faith discussion here, just jötunn-ry.

  76. angech wrote “Having been called out in the past for not fully quoting comments I guess I can do a tu quoque?”

    LOL, it turns out that angech’s “tu quoque” is (a) incorrect as my point does not depend on the parts I didn’t quote and (b) relies on selective quoting of what I wrote, oh the irony! ;o)

    O.K,. the full paragraph is:

    Climate field reconstruction (CFR) methods; MBH 1998 and 1999
    “The NRC committee stated that “The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that
    includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators”. It said “Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium”, though there were substantial uncertainties before about 1600″”.

    angech claims: The NRC did not say “the recent warming is unprecedented.” Mann et al said that.

    I didn’t say that the NRC said it, the bit I quoted was:

    “The NRC committee stated that “The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators”

    [emphasis mine]

    Which makes it clear that it was Mann that said it, so angech begins his tu-quoque by misrepresenting what I wrote. Angech, you owe me an apology.

    angech goes on to say

    The part that DM leaves out says clearly, plausible only, with substantial uncertainties before 1600. I will append the bit he missed by accident.

    Now that is just downright dishonest. This is what I wrote:

    Even angech’s own sources refute him. His original claim was:

    These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.

    [emphasis mine]

    and he supports that with:

    “The NRC committee stated that “The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that
    includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators”

    So it is clear that I am saying that your evidence contradicts your original claim, not the weaker claim after your goal-post shift. You claimed “Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.”. You claimed with certainty that these warming events happened a number of times, so if it is plausible that it is warmer now, that contradicts your certain claim. Also our records don’t stop at the end of the 20th century (this is 2018) and it has warmed since then, so the plausibility has increased. Secondly, the previous warm conditions were during the medieval warm period but that warming too place over a much longer timescale, so it isn’t equivalent to the modern 150 year warming.

    Thus the bit you say I left out is irrelevant to the point I made, but angech’s trolling has wasted more of my time.

  77. Dave_Geologist says:

    angech
    As ice retreats, frozen mosses emerge to tell climate change tale. Dating of plants suggests summer’s hotter now than it’s been in at least 45,000 years, if not longer

    Thirteen samples collected between 1200 and 1400 m asl returned plant ages between 9.0 and 9.8 ka, supporting peak warmth in the earliest Holocene, which has now been surpassed. And most interesting 33 dates from 27 unique ice caps revealed rooted plants with 14C ages >40 ka … Collectively, these data indicate that many landscapes exposed during recent summer warming were continuously ice-covered since the LIG. Contemporary warming is now causing some ice caps on Baffin Island to shrink to dimensions smaller than at any time in the past ~115 ka, including the HTM, when summer insolation was 9% higher than at present.

    So, a warming spike that not only failed to be picked up in hundreds of proxy records, but also very kindly spared Baffin Island? I think not.

  78. angech wrote

    “Sorry DM I have not changed my position. No goal post shift. Read my comment again noting “have happened” refers to events ” past temperatures, but only locally” which are well known and real.”

    This distinction makes angech’s argument mere sophistry. Depending on what you take to mean “local” (variability increases as the size of the region decreases) then there may be instances of temperatures rising a degree over the course of 150 years, if you pick a region small enough. But what does that tell us about the “Hockey Stick”? Precisely nothing.

    Even then, angech still has provided no evidence whatsoever that this “has happened”, just a claim that they are “well known and real”. Well, give us a specific example then!

  79. angech says:

    BBD “I dispute this. Please describe a plausible physical mechanism capable of producing a ~1C spike in GAT lasting ~150 years.”
    I would like your opinions on the statistical probability of such events existing [my statement] rather than sidetrack to the question of how as you have an excellent understanding of the statistics involved.
    I note the question of attribution and detection of such physical mechanisms has been raised by several other people above. Plausible is a good standard.

  80. angech says:

    dikranmarsupial says:
    “This distinction makes angech’s argument mere sophistry.”
    No, I did not conflate the two arguments.I did not goal shift. Saying I did is not correct.

    “Depending on what you take to mean “local” (variability increases as the size of the region decreases) then there may be instances of temperatures rising a degree over the course of 150 years, if you pick a region small enough. But what does that tell us about the “Hockey Stick”? Precisely nothing”.
    I actually agree and agreed with this point of yours multiple times above.

    Even then, angech still has provided no evidence whatsoever that this “has happened”, just a claim that they are “well known and real”. Well, give us a specific example then!.

    Support? “well known and real” local.
    “.Pages-2k consortium suggests the warming was not globally synchronous: “Our regional temperature reconstructions also show little evidence for globally synchronized multi-decadal shifts that would mark well-defined worldwide MWP and LIA intervals. Instead, the specific timing of peak warm and cold intervals varies regionally, with multi-decadal variability resulting in regionally specific temperature departures from an underlying global cooling trend.”
    1..The Medieval Warm Period (MWP) also known as the Medieval Climate Optimum, or Medieval Climatic Anomaly. It is thought that between c. 950 and c. 1100 was the Northern Hemisphere’s warmest period since the Roman Warm Period.
    2. The Roman Warm Period, or Roman Climatic Optimum, has been proposed as a period of unusually warm weather in Europe and the North Atlantic that ran from approximately 250 BC to AD 400.[1]
    3 Vikings in Greenland. 4 Coming out of the LIA etc.

  81. “I would like your opinions on the statistical probability of such events existing [my statement] rather than sidetrack to the question of how as you have an excellent understanding of the statistics involved.”

    You have so far provided no evidence that such events existed, if you can’t suggest a plausible physical mechanism, why should we accept your assertion when you have not given a single verifiable example.

  82. Dave_Geologist says:

    Dear oh dear angech, you do realise that battle was fought and lost a decade or more ago?

    And that ATTP’s post refers to the plethora of subsequent hockey sticks? So even if “your side” had won (it didn’t, at least outside of fora where dishonesty is the order of the day), that would be irrelevant today? About on a par with “Al Gore is fat”.

  83. angech says:

    dikranmarsupial
    I have no wish to attack you personally.
    I realise that your belief and commitment is very strong and unwavering and that my intransigence in the past has caused you to be quite upset with me.

    My statement however stands.

    “These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.”
    Could I emphasis the word locally.
    It makes a big difference to me, my arguments and your view of them.
    ATTP said “I think the proxies have a good enough resolution for us to see if there previous periods with warming comparable to the modern warming”
    All the best.
    Thank you.

  84. BBD says:

    I would like your opinions on the statistical probability of such events existing [my statement] rather than sidetrack to the question of how as you have an excellent understanding of the statistics involved.

    If no plausible physical mechanism exists that could produce a global warming of ~1C and ~150y in duration, there is nothing further to discuss.

    Since you cannot (will not) answer this question, I’d say we are done here.

  85. Marco says:

    Well, there *is* a plausible mechanism, but then we’re missing the evidence for *that* also in the data. Think of a major (but short duration) outgassing event of greenhouse gases, or some sudden significant increase in solar output for a short period of time.

  86. BBD says:

    @Marco

    But as izen says, a significant GHG outgassing would show up as a negative carbon isotope excursion and a significant increase in solar output would also leave a trace in the isotopic archives.

    So when I used the term ‘plausible’ I fully intended it to mean ‘plausible in the light of the proxy evidence currently available’. Which of course pretty much discounts GHG outgassings or spikes in solar output. Also, what about the long term residence of carbon cycling around for millennia?

    And where’s my sea level rise????

    🙂

  87. zebra says:

    Marco,

    Let’s say you established that some such event could occur, and that all the proxies would miss the consequences, and so on.

    What would change? It would still be the case that physics predicts that an increase in CO2 should cause an increase in energy in the system, manifested by GMST increase among other things.

    -We know that humans are increasing the CO2.
    -We observe the temperature increase, as well as the other predicted phenomena.

    Why would our conclusion change– that the prediction from physics is correct, and human emissions are causing the effect?

  88. Marco says:

    Conclusion wouldn’t change, but that’s maybe why we now see a concerted effort to deny that the rise in CO2 is anthropogenically driven.

  89. paulski0 says:

    Kevin Anchukaitis,

    Thanks for posting here and for the link to the Pages2K-PMIP3 paper. Figure 6b showing how well PMIP3 simulations and the Pages2K reconstruction agree on variability is remarkable to me.

    I think one really large question mark is still the Southern Hemisphere, which from the more limited proxy data and reconstructions look different than the modeled forced response.

    The quote from the paper suggests people are focusing on model errors, but presumably errors/limitations of the proxy data and methods are being addressed as well? One particular feature of all the SH records in Pages2K is a complete lack of response to the 1815 Tambora eruption, which seems implausible to me.

    If I look at the instrumental records for these continents there is no clear response in South America from Mt Agung, El Chichon or Pinatubo, but this could be due to coincident strong El Nino events. Meanwhile the influence of all three eruptions is clear and similar to the average modeled magnitude in the instrumental data for Australia and Antarctica. I can’t see a plausible reason why the much stronger Tambora eruption would not be similarly visible in an accurate reconstruction.

  90. I suppose that is a plausible mechanism for variability in some of the paleo records

  91. Chubbs says:

    Per the steady rise in OHC, there is a large global energy imbalance so the current temperature spike is going to continue to increase and last much longer than 150 or 200 years. Now that we are clearly moving away from the Holocene, comparison to the eemian is becoming a more important technical issue.

  92. zebra says:

    Marco,

    “…a concerted effort to deny that the rise in CO2 is anthropogenically driven.”

    Really? That’s a new one on me, but then I don’t follow the denial-o-sphere much at all. What is the claim for such a source?

  93. Marco says:

    No need to follow the denial-o-sphere, you can actually find this stuff in the scientific literature! Essenhigh 2009, for example, and we’ve had a discussion here, not too long ago, about a paper by Hermann Harde from 2017 arguing the same. And it seems there is yet another paper coming soon, by one Ed Berry. Of course, there’s also Murray Salby, but he hasn’t yet managed to publish a paper as far as I know (it’s in one of his books, though).

  94. zebra says:

    Marco,

    OK. I thought the Harde post was about peer review stuff so I didn’t pay attention to the substance.

    Is there a synopsis of the argument somewhere? Burning fossil fuels doesn’t produce CO2?

  95. Marco says:

    Synopsis? Fail to understand the difference between residence time and adjustment time of CO2 molecules – make some oversimplified equations based on that failure – conclude that only a fraction of the increase in atmospheric CO2 is from anthropogenic sources.

    That it requires an alternative source that has actually emitted *thousands* of gigatons of carbon over the last few centuries (rather than the estimated many hundreds from fossil fuels), as well as another sink that has taken up more than those thousands of gigatons…who cares?

  96. zebra says:

    Marco,

    Well OK then. They’ve convinced me. (sarcasm)

    Similar to the paleo-spike business you were talking about, though. Fails Ockham’s Razor pretty dramatically. And, unfortunately, also creates the false illusion of equivalency when it is refuted.

  97. The Very Reverend Jebediah Hypotenuse says:
  98. The residence time vs adjustment time misunderstanding is significant. Diffusion to sequestering sites is not an exponential decay (residence time) process but is fat-tailed (adjustment time). An especially common D-K problem among tech-types who know just enough to be dangerous.

  99. Mal Adapted says:

    Sorry, accidentally clicked Post too soon. Mod(s) please delete my comment of April 25, 2018 at 8:12 pm.

    angech:

    I agree the profiles are settled. I point out that the ways we have of measuring lead to a flat stem.
    I point out, as MM et al did, that there are uncertainties that worsen as we go back in time.I make the observation that a rise [or fall] in temperature over 150 years of the same magnitude is possible in the past 1000-3000 years within the error bars and without being able to be shown up due to the statistical nature of the proxies as we go further back in time beyond the scope of most tree ring studies.
    That is all. Use it as you will.

    I’m afraid I can’t use it at all, since you haven’t convinced us how there could have been a transient episode of global warming of up to a degree C, followed by a return to the long-term GMST, within 150 years: you know, physics. Without a plausible mechanism, the probability that such a thing could happen remains on the same order as that for “pigs might fly”. It appears my attempt to point out that how agreeably the issues you raise are discussed is up to you, has had no effect on you whatsoever.

    Just sayin’!

  100. angech says:

    Mal Adapted says:
    “I’m afraid I can’t use it at all”
    agreeably, That’s OK.
    Marco and Izen put up some convincing scenarios as to how.
    Both refuted such scenarios as plausibly having happened though.

  101. Marco says:

    I would not call my scenarios “convincing”. I realize I should not have used the term “plausible mechanism”, because a major but short duration GHG pulse simply isn’t very plausible either. Equally problematic would be to explain a sudden and short duration significant increase of solar output, well beyond what we’ve seen in our time.

    In other words, the “what if” options I provided would be scenarios that would result in a short-lived rapid warming followed by rapid cooling episodes, but are as such scenarios for which we would have no mechanistic explanation. And that comes on top of us having to somehow miss those events in the paleoclimatologic data, too.

  102. I asked:

    You have so far provided no evidence that such events existed, if you can’t suggest a plausible physical mechanism, why should we accept your assertion when you have not given a single verifiable example.

    angech replied:

    dikranmarsupial
    I have no wish to attack you personally.
    I realise that your belief and commitment is very strong and unwavering and that my intransigence in the past has caused you to be quite upset with me.

    I find this deeply offensive, rather than answer my request for a single verifiable example of the temperature changes you claim exist, you have implied that my position is ideological and fixed, both of which are deeply insulting when applied to a scientist, and actually not true. I am perfectly willing to change my position, IF you supply the evidence, but I have a low tolerance for this kind of rhetorical bullshit.


    My statement however stands.

    “These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.”
    Could I emphasis the word locally.
    It makes a big difference to me, my arguments and your view of them.
    ATTP said “I think the proxies have a good enough resolution for us to see if there previous periods with warming comparable to the modern warming”
    All the best.
    Thank you.

    Note lack of a single verifiable example of these local temperature changes, and yet another selective quote, ATTP actually wrote:

    angech,
    You keep claiming this, but I don’t think it is correct. I think the proxies have a good enough resolution for us to see if there previous periods with warming comparable to the modern warming. There is little evidence to suggest that there has been.

    The bit that you omitted oddly enough, shows that what he wrote was not supporting your position but opposing it.

  103. “dikranmarsupial says:
    “This distinction makes angech’s argument mere sophistry.”
    No, I did not conflate the two arguments.I did not goal shift. Saying I did is not correct.”

    sophistry means “the use of clever but false arguments, especially with the intention of deceiving.”. Your argument is sophistry because the existence of local temperature changes does not tell you anything about the global/hemispheric “hockey stick” proxy reconstructions. Your lack of good faith in this discussion is clear from your comments on climate skeptic blogs.

  104. BBD says:

    I realize I should not have used the term “plausible mechanism”, because a major but short duration GHG pulse simply isn’t very plausible either.

    That’s the point 🙂 As is the inherent implausibility of such an event leaving no trace in the proxy evidence whatsoever. So you were entirely justified in asking for a plausible mechanism because that is what angech needs to supply at this point in the discussion.

    And he hasn’t.

  105. Dave_Geologist says:

    angech et al.
    I’ll follow up on what others have said with a few examples. I’ll pass on the sudden hot sun event as that’s more ATTP’s territory. Beyond pointing out that there would be detectable consequences in the palaeo record. C14 perturbations for sure, and as that’s been studied to death in support of age dating, tied to tree-rings (with annual resolution, at least in principle), volcanoes and extraterrestrial events, the chances of science missing something that would have to have been an order of magnitude bigger than natural variability, is vanishingly close to zero. And referring to my earlier post where ice in Baffin Island is melting today, that didn’t melt even when NH insolation was 9% higher than today.

    Some weird blip in the Milankovitch cyles? Apart from probably violating the laws of physics, why would its palaeo impacts be undetectable when we can detect those of the actual cycles? And doesn’t it need amplification, albedo change due to ice melting, and ocean degassing? Can that happen within a century? Show your working.

    How about volcanoes? Also intensively studied in the palaeo record, and even the biggest supervolcanoes cause cooling not warming, due to aerosols overwhelming CO2 on the timescale of injection. To get warming you need sustained addition of CO2, which cumulatively overwhelms aerosols because of their long vs. short atmospheric residence times. You basically need a Large Igneous Province, which is kinda hard to hide, what with the enormous pile of black basalt and all. Geologists would have noticed. Trust me, I’m a geologist 😉 . And you can’t hide it under the sea. One so young would still be hot and form an enormous shallow bank or a microcontinent-sized island. And you probably can’t do it in 100 years anyway. There are energy conservation constraints and rate-of-mantle-flow constraints (the main mechanism is decompression melting, so to melt a lot of mantle fast, you need very fast upwelling; and because of disequilibrium melting, you’d get a distinctive chemical signature, different from normal LIPs).

    Your best bet for something like AGW would be the PETM or one of the subsequent ETMs. Which of course is why the’re studied so much. Plausibly explained by Milankovitch-style cycles triggering a positive feedback with melting of methane hydrates
    or permafrost, or lavas intruded into petroleum source rocks (I prefer the former as less serendipitous, despite having seen the rocks, and seen the gas/fluid escape vents on seismic). Note that this is not a case where science can’t come up with a plausible explanation. It’s one where there are three or four plausible explanations, but we can’t yet tell which one is right. Science deniers have a strange habit of conflating those two very different situations. The problem, of course, is if we can see the 13C, CaCO3 and other signals in palaeo data from 50 million years ago, how come we can’t see them from 500 or 5,000 years ago?

    So, flying pigs and unicorns, or Ockham’s razor. I’m with William on this one.

  106. Reminder of angech’s original claim:

    These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.

    Note, it is “temperature changes equivalent to the modern 150 year warming” so it is the magnitude (about 1C) and rate (150 years) that is involved for the local change to be “equivalent”

    angechs quotes:

    “.Pages-2k consortium suggests the warming was not globally synchronous: “Our regional temperature reconstructions also show little evidence for globally synchronized multi-decadal shifts that would mark well-defined worldwide MWP and LIA intervals. Instead, the specific timing of peak warm and cold intervals varies regionally, with multi-decadal variability resulting in regionally specific temperature departures from an underlying global cooling trend.”

    That just says that there are regional temperature changes in the data, it says nothing about their magnitude or rate that supports anchech’s claim.

    1..The Medieval Warm Period (MWP) also known as the Medieval Climate Optimum, or Medieval Climatic Anomaly. It is thought that between c. 950 and c. 1100 was the Northern Hemisphere’s warmest period since the Roman Warm Period.

    That is a statement about an absolute temperature, not about a warming (i.e. an increase in temperature), as per angech’s original claim. As far as I can see, there is no evidence that wither the rate or magnitude of the warming leading to the MWP is “equivalent” to that seen in the “modern 150 year warming”. The magnitude of the change is smaller (remember that plot ends in 2004) and happpened over a much longer time-scale. So that example fails.

    2. The Roman Warm Period, or Roman Climatic Optimum, has been proposed as a period of unusually warm weather in Europe and the North Atlantic that ran from approximately 250 BC to AD 400.[1]

    So angech is going to use a proposed warm period as an example of warming events that “have happened”, note assertion of certainty. Again there is no information there about the magnitude or the rate of warming. So that example fails.

    3 Vikings in Greenland.

    That isn’t a verifiable event, angech doesn’t even provide any evidence this was more than propaganda used to encourage other vikings to explore westward. No information about the rate or magnude of the warming. Example fails.

    4 Coming out of the LIA etc.

    The etc. is rather ironic given that angech was obviously struggling after the first one. Again looking at the temperature reconstruction I gave earlier, there appears to be very little warming from the depth of the LIA until the last 150 years, which obviously doesn’t count! Again, example failed.

    So angech, where are your verifiable examples where the magnitude and rate of warming is “equivalent” to what we have seen over the last 150 years?

  107. Must have messed up the tags again. The picture I intended to include was this one:

  108. Marco says:

    jsam, Dessler has already “enjoyed” it:

  109. Dave_Geologist says:

    So, I guess that mean we have unicorns to thank for getting us in and out of ice ages? Who’da thunk it!

    More generally, I do struggle to see how measuring a system not in equilibrium can tell us what it will be like at equilibrium. At best, a minimum estimate given the physical arguments that there is warming in the pipeline. Ditto using El Nino, cloud or other perturbations. They can only tell us about the response on the time-frame of the “oscillation”, which is shorter than the time basic physics tells us to expect for equilibrium.

  110. Mal Adapted says:

    angech:

    Marco and Izen put up some convincing scenarios as to how.
    Both refuted such scenarios as plausibly having happened though.

    Doc, you’re telling us you’re convinced there could have been 150-year periods when GMST rose as much as a degree, then returned to its long-term value, even after it’s been explained why that’s simply not plausible scientifically. You are the very model of motivated reasoning.

    That is, you’re a pseudo-skeptic. If you want to act like a genuine skeptic, ask yourself who benefits most from public confusion about settled science, and why you’re willing to give the benefit of your doubt to transparently self-serving nonsense.

    “There are none so blind as those who will not see.” –English proverb

  111. zebra says:

    Dave G,

    “how come we can’t see them from 500 years ago”

    More important, going back to the point I made to Marco earlier: How come we can’t see “them” now?

    The claim is that some phenomenon– however far-fetched– resulted in a GMST spike somewhere in the last 18K years or so is only relevant if it is also claimed that it is happening now, and, through some convoluted narrative, is the “real” cause of the current spike.

    So, I would say to @angech: For the sake of argument, let’s agree that such an event happened in the past. So what? Why should we care, and why should we expend any effort looking for it in the past? That was then, this is now.

  112. zebra says:

    “The claim that some phenomenon….is only relevant…

  113. Mal Adapted says:

    Me, to angech:

    You are the very model of motivated reasoning.

    By ‘you’ and ‘Doc’, of course, I’m referring to the avatar known here as ‘angech’, purportedly a Doctor of something. I eschew idle speculation regarding the sincerity of the (presumably) human mind behind the avatar’s words, beyond the obvious evidence of its dogged rebunking of multiple ridiculous AGW-denier memes (e.g. ‘Vikings in Greenland’) on this blog, of all places. The same evidence suggests he’s not being paid: who would pay for his comments here ;^{ (‘pointed sarcasm’)?

  114. Dave the Geognostic: “So, I guess that mean we have unicorns to thank for getting us in and out of ice ages? Who’da thunk it!”

    Unicorns, like climate models, are not things.
    Climate forcings, OTOH, are as thingy as a rhinoceros, and while you can’t model metaphysical entities, things are fair game.

    This is not to say that uncorns are absent from the fild in the climate wars- most of the arsenal of climate denial consists of factoids and rigid designators in the null set.

  115. angech says:

    Thanks, Willard for restoring my faith in human nature. Mojo back. Off to see JCH laugh at me about the next monthly temperature rise at Judith’s. Interesting post on ECS, again by Nic.

  116. Dave_Geologist says:

    Since you waxed almost Sokalian at the end, Russell, I was tempted to insist that unicorns are things because my reality is as valid as your reality. But you rescued me from that absurdity by omitting the trigger-word “signifier” 🙂 .

    My serious point was that if you come up with an equilibrium climate sensitivity which implies insufficient positive feedback to explain glaciations and deglaciations, you’ve probably done something wrong. Or not measured what you thought you were measuring (think faster-than-light neutrinos). Especially in light of Dessler’s pre-deconstruction (which in fairness would have still been in press when LC18 was finalised). But I bet he’d talked about it earlier, and ploughing a lonely furrow risks leaving yourself out on a limb when someone’s cut half-way through the trunk of the tree already and the saw is still whirring (with apologies for the mixed metaphor!).

    Michael Mann’s comment is the best

    The old joke “your new paper is both novel and valid! Unfortunately, the parts that are valid are not novel and the parts that are novel are not valid”.

  117. O.K. so angech can’t admit that he cannot provide any valid examples to support his claims. Plus ca change…

  118. JCH says:

    angech – Nick Stokes has indicated it is possible April will sprout the highest anomaly in the last 12 months, pause for a moment for a hiatus in the politicized science you are indulging in over at CargoCult Etc., how does that happen in the midst of a La Niña and low solar if climate sensitivity is low?

    It is looking like NOAA ONI for April will drop below .5 ℃. Darn. I was hoping to have something like .93 ℃ as the final number for 17-18’s “big chilla” La Niña event.

  119. angech says:

    JCH
    “angech – Nick Stokes has indicated it is possible April will sprout the highest anomaly in the last 12 months, pause for a moment for a hiatus in the politicized science you are indulging in over at CargoCult Etc., how does that happen in the midst of a La Niña and low solar if climate sensitivity is low? ”
    Not sure which set the anomaly is in, can you clarify. I went to Nick’s site but his latest post is on the GISS rise last month. Let us wait and see if he is right.
    “It is looking like NOAA ONI for April will drop below .5 ℃.” Yeeeess, possibly. As a 3 month index ending in April this time it has to merge 7 weeks of -0.6/7 with 5 weeks of rising to -.03. It could be close.

  120. angech says:

    “1..The Medieval Warm Period (MWP) also known as the Medieval Climate Optimum, or Medieval Climatic Anomaly. It is thought that between c. 950 and c. 1100 was the Northern Hemisphere’s warmest period since the Roman Warm Period.
    2. The Roman Warm Period, or Roman Climatic Optimum, has been proposed as a period of unusually warm weather in Europe and the North Atlantic that ran from approximately 250 BC to AD 400.”
    Two examples that I, and some other people, would think are valid examples of a warming period that laste 150 years.

  121. dikranmarsupial says:

    angech has ignored what I wrote yet again. You claimed:

    These can give an indirect record of past temperatures, but only locally. Such records indicate that Temperature changes equivalent to the modern 150 year warming have happened a number of times in the past 3000 years.

    That is a claim about “warming”, i.e. a change of temperature, so the rate of change and its magnitude is relevant. So neither of those examples are “equivalent” to the warming of the last 150 years, which has been unusually rapid, in neither case is there an indication of the rate of warming, or the magnitude of the warming relative to its starting point.

    Also you claimed that such warming periods “had happened” (no uncertainty), as I pointed out, the RCO you mentioned has only “been proposed” and hence does not support your claim.

  122. Dave_Geologist says:

    angech, in case you haven’t noticed, “Europe and the North Atlantic” is not the globe. Not even close.

  123. dikranmarsupial says:

    D_G angech did mention that he was talking about local examples of warming. Even if he could come up with a verifiable example that was “equivalent to the modern 150 year warming”, it is still not clear what relevance that has to the hockey-stick reconstruction(s). It is a good way to waste out time and energy though. A lot less effort went into merely repeating two of his examples than I put in to explaining why they were invalid.

  124. Dave_Geologist says:

    valid examples of a warming period that laste 150 years

    I think somewhere earlier in the trail I asked for a valid example, and specified that it had to be global and synchronous as well as big enough and short enough. So I should have been clearer. I’m not challenging that those events exist, because that’s irrelevant. To turn them into valid examples angech has to demonstrate that they’re not just local.

  125. BBD says:

    In which angech demonstrates that fake sceptics *never* admit that they are wrong, no matter how much bad faith is required to keep on posting garbage.

  126. JCH says:

    The best name for it so far – I think from Russell – is MDP: Medieval Dumb Period.

  127. angech says:

    “Dave_Geologist says: angech, in case you haven’t noticed, “Europe and the North Atlantic” is not the globe. Not even close.”
    Hence “These can give an indirect record of past temperatures, but only locally”
    BBD “no matter how much bad faith is required to keep on posting garbage.”
    MWP and RCO are rubbish? Not so or Wiki would correct, right? I did not make up the names time length and warming no matter what you wish to throw at it. Not my fault it is on the web and out there.

  128. angech,
    Don’t believe everything you read on the internet.

  129. LetoLeto says:

    angech: “MWP and RCO are rubbish? Not so or Wiki would correct, right?”

    Come on angech. You’re a doctor, supposedly. Put down complete thoughts, address the points actually being made by others, and don’t resort to trivial straw-men caricatures of what they are saying. Really, you can do better.

  130. JCH says:

    Seriously, he can’t.

  131. dikranmarsupial says:

    angech wrote “MWP and RCO are rubbish?” not necessarily, they are just not examples of warming (verb) or change of temperature equivalent to the warming of the last 150 years that you claimed.

  132. Dave_Geologist says:

    Still having trouble with that local vs. global thing, eh angech?

    This may help.

  133. angech says:

    Look, I think the piling on is really healthy, happy to wear it and argue it to the hills, but only with the lighter weights.
    I want to avoid a Dikran vs angech comment thread, at all costs. I think Dikran’s point of view is explicit, and clear and totally different to mine.
    He is a lot more entitled to his views due to his senior status here and his scientific knowledge and expertise.
    That is not to say that I will not put up an alternative point of view and and discuss it with the rest of you if you address the same arguments.
    ATTP’s point
    “It’s almost 20 years since the publication of the first hockey stick paper (Mann, Bradley & Hughes 1998). The hockey stick refers to millenial temperature reconstructions that look a bit like a hockey stick; a period of centuries during which temperatures appear reasonably flat, or cool slightly (the shaft), followed by a period of rapid warming starting in the mid-1800s (the blade)”
    is something I concur with.
    I point out, mathematically why this must happen with any older proxy record.
    I point out that the standard deviations grow as we go back in time and are large enough to easily encompass 1C ranges of temperature for 150 years without it having to trouble the records.
    It cannot trouble the records because the SD is much larger than 1C.
    So why the fuss?
    Why do we have to say the past 3000 years ran along with nary a squeak off the railroad straight hockey shaft?
    Internal variation too large lets denialists claim a slight risk to the scientific consensus?
    Even though when we admit it is large enough short term we can show observational ECS is too low?
    Not my problem, nor yours either if you man up to the scientific facts and work with them.

  134. Dave_Geologist says:

    Did you forget about the dog that didn’t bark angech?

    Why didn’t the ice melt during that mysterious warm century hiding in your uncertainty envelope? A special kind of warmth that doesn’t melt ice?

  135. zebra says:

    angech,

    “why the fuss”

    That was my question to you, although it was embedded in a comment to Dave G.

    These guys are “piling on” out of habit, but you are not addressing the relevant question:

    I said, for the sake of argument, let’s assume that there was such a spike in GMST the past 3,000 years. So what? That was then, this is now. How does it affect the consensus about CO2 causing the current increase in system energy, which shows up as increasing GMST and the other well-known phenomena?

  136. angech says:

    Dave_Geologist says:
    “Why didn’t the ice melt during that mysterious warm century hiding in your uncertainty envelope? A special kind of warmth that doesn’t melt ice?”
    The problem is, Dave, that you would have to show that it did not melt, I guess.
    Matthews, J.A. and Briffa, K.R. , 2005: The ‘Little Ice Age’:shows periods of rapid melting prior to glaciation recommencing.
    In the non existent MWP and RCO.

  137. BBD says:

    angech

    BBD “no matter how much bad faith is required to keep on posting garbage.”
    MWP and RCO are rubbish? Not so or Wiki would correct, right? I did not make up the names time length and warming no matter what you wish to throw at it. Not my fault it is on the web and out there.

    >a href=”https://andthentheresphysics.wordpress.com/2018/04/22/20-years-of-hockey-sticks/#comment-117049″>Learn to read. Or stop deliberately dodging the point, whichever is the problem.

  138. BBD says:

    In the non existent MWP and RCO.

    Which were neither global nor synchronous nor as warm as or warmer than the present. Learn to read, or stop being disingenuous and ‘missing’ the point.

  139. Dave_Geologist says:

    Yawn… you still don’t get local vs. global angech. For clarity, I totally accept that the LIA and MWP were real, although if you define them loosely enough to be global neither is globally synchronous, and if you define them tightly enough to be synchronous (on the 150-year scale under discussion) they’re not global. So as I said before, no cigar.

    The non-barking dog I was referring to was the Baffin Island ice I referenced up-thread. The newly-melted ice which uncovered mosses so old they have no C14 left (so more than 40,000 years old). Not in NW Europe, so unsurprisingly, didn’t melt during the MWP. But melting now. Funny that.

    And I’m not falling for the Little Ice Age bait-and-switch. You claimed a globally synchronous warm period, so the LIA is irrelevant.

    And in any case there are only two mentions of “glaciation” in Matthews & Briffa, neither of which supports “rapid melting prior to glaciation recommencing”, and one of melting, ditto. Perhaps you can narrow down the quote? If you’re referring to “glacier regrowth or recrudescence in the Sierra Nevada, California, following their melting away in the Hypsithermal of the early Holocene”, that was anything but rapid. The Hypsithermal is the “Holocene Climatic Optimium” or the “HTM” referred to in the Baffin Island mosses (that would be the one when the ice didn’t melt, BTW). The interval roughly 9000 to 5000 years ago. Please explain how a 4000-year long warm interval identified in the proxy records, and followed by 5500 years of cooling into the LIA, compares to our present-day hockey-stick “blade”. Or show where else in the paper MB05 present evidence of a “blade”.

  140. JCH says:

    Mann said he wanted to constrain the MWP, which they took to mean he wants erase it.

    Websters is not on their shelf.

    Proof. Schmidt called the MWP “putative”, and that sounds like an insult to the MWP. The word sounds like an insult. “You putative sob.”

    Which is why, from now on, it’s the MDP: Medieval Dumb Period.

  141. angtech should talk to a broader spectrum of European archaeologists- among the many surprizes of the last decade are solidly dated evidence that the Vikings grew grapes in 9th century Denmark- the North Atlantic climate that allowed the discovery of Iceland permitted further voyages East in the next few generations.

  142. Dave_Geologist says:

    Cool, Russell

    Henriksen himself discovered the two centuries-old wine pips in a sample of earth at the site of a Viking settlement at Tissø. Analysis of the pips found one to date from the Viking era and the other from the Iron Age.

    Grapes in Denmark. In the Iron Age. Which in Scandinavia means before 800 AD. Long before the Medieval Warm Period. So you could grow grapes in Denmark with a global temperature anomaly of -0.2°C to -0.5°C (graph up-thread). So Viking grapes in the MWP are no big deal. They could grow when it was even colder, much colder than today’s anomaly of around +1°C. Good of you to set that old canard to rest.

    Probably not what angech wanted to hear though.

    Of course it’s much easier nowadays. They could no doubt have re-started making wine in Denmark before the 21st Century, but it was only legalised in 1999.

  143. angech wrote “I want to avoid a Dikran vs angech comment thread, at all costs.

    In other words, I have shown that angech’s examples are invalid and do not support his claim, and he has no counter-argument, but is unwilling to admit that he was wrong.

    “That is not to say that I will not put up an alternative point of view and and discuss it with the rest of you if you address the same arguments.”

    There is no problem with this, but if you make claims that are obviously wrong then you have to expect them to be challenged. If you can’t meet the challenge and can’t admit you were mistaken, then you are violating the norms of scientific discussion and you will invite criticism.

    So you you admit that your examples are invalid because they don’t show evidence of a rate of change in temperature equivalent to that seen over the last 150 years or a magnitude of change equivalent to that seen over the last 150 years?

  144. angech says:

    zebra says: April 29, 2018 at 1:08 pm
    ” let’s assume that there was such a spike in GMST the past 3,000 years. So what? That was then, this is now. How does it affect the consensus about CO2 causing the current increase in system energy, which shows up as increasing GMST and the other well-known phenomena?”

    CO2 should cause warming with an increase in concentration in the atmosphere.
    A general, but not complete consensus.
    However observations are falling badly behind computer model predictions of what the temperature rise should be.
    Why?
    The physics may not be totally right somewhere. Unlikely.
    One or more of the many climate model assumptions appears wrong. Bing!
    Or as AD in the next thread says, natural variability may be playing up with the temperature rise and could do so for the next 155 years or more.
    Hence the problem with the consensus. If natural variability can effect ECS and hence temp for a long period then many of the skeptics [me included] can logically introduce an element of doubt into the consensus. Some of course say CO2 has no effect and that the warming spike to date could be explained purely from natural variability, not CO2.
    Others that ECS may be lower than expected so that the warming will not be as severe as predicted.
    Such points are valid while observations keep deviating from models.
    If they persist they would demand an investigation into why.
    If warming does return to the pattern expected of it then this all would be moot.
    Your answer in brief is that a consensus tends to ignore and belittle data, people and ideas that do not conform with the consensus, even when they have elements of truth that should be welcomed into a fuller understanding.

  145. angech says:

    addendum CO2 causes warming with an increase in concentration in the atmosphere.
    I believe Roy Spencer guarantees it which is good enough for me.

  146. angech wrote “However observations are falling badly behind computer model predictions of what the temperature rise should be.”

    more unsubstantiated rubbish

  147. BBD says:

    Such points are valid while observations keep deviating from models.

    Nope.

    The suggested mechanisms behind the slowdown in the rate of surface warming include:

    – increase in wind-driven ocean circulation (England et al 2014)

    – predominance of ENSO La Nina state (Banholzer & Donner 2014)

    – increased aerosol negative forcing (Ridley et al. 2014)

    – reduction in solar output during SC24 (SSN)

    There is evidence that when the CMIP5 forcing estimates used for AR5 are updated to bring them into line with real-world forcing history, then modelled global average temperature comes into much closer agreement with observations (Schmidt et al. 2014). This would suggest that model physics – and so emergent behaviours like model sensitivity – are reasonably accurate.

  148. BBD says:

    If warming does return to the pattern expected of it then this all would be moot.

    Arguably already has so contrarian talking points were and remain invalid.

    Your answer in brief is that a consensus tends to ignore and belittle data, people and ideas that do not conform with the consensus, even when they have elements of truth that should be welcomed into a fuller understanding.

    And that’s just self-serving contrarian nonsense.

  149. zebra says:

    angech,

    I’m not asking for all the reasons why you may doubt the consensus. Just about the hypothetical spike in the past. That’s what you’ve mostly been discussing, right?

    How is that discussion about the past relevant to what is happening now?

  150. Skol, Dave.

    The second worst hangover from this discovey must fall on Mark Steyn, who went over the top in claiming the Vikings made wine in Greenland

    First prize for archaeological revisionism goes to the President of the United States

    https://vvattsupwiththat.blogspot.com/2018/04/hundred-million-year-apprenticeship.html

  151. JCH says:

    Well, can we safely say the Vikings drank a lot of booze in Greenland?

  152. jacksmith4tx says:

    Russia builds huge floating radioactive water heater and sends it to the Arctic:
    “The nuclear power plant has two KLT-40S reactor units that can generate up to 70 MW of electric energy and 50 Gcal/hr of heat energy during its normal operation.”
    https://www.npr.org/sections/thetwo-way/2018/04/30/607088530/russia-launches-floating-nuclear-power-plant-its-headed-to-the-arctic

    Human error being what it is, this seems like a spectacularly dangerous idea.

  153. Dave_Geologist says:

    angech

    However observations are falling badly behind computer model predictions of what the temperature rise should be.

    Only in the eyes of the statistically ignorant.

  154. Dave_Geologist says:

    even when they have elements of truth that should be welcomed into a fuller understanding.

    Well, yes, but that rather presumes facts not in evidence 😉

  155. angech says:

    dikranmarsupial says:
    May 1, 2018 at 9:49 am
    ” Getting a GCM that reproduces the broad responses to changes in the forcings on multi-decadal/centennial scales, then that might be reasonable. However as soon as you look at shorter timescales or regional/sub-regional spatial scales, then I would have thought that the dependence on internal variability increases, and the models can’t be expected to reproduce that, only simulate it, which is all that is required for a Monte-Carlo simulation.”
    On the next thread and different subject matter but pertinent to the concept of variability and time effects that I was discussing in a related vein here.
    I thank him for this observation.

  156. angech, don’t change the subject, provide evidence to support your claim that “observations are falling badly behind computer model predictions of what the temperature rise should be.”

  157. angech says:

    dikranmarsupial says: May 1, 2018 at 3:19 pm
    angech, don’t change the subject, provide evidence to support your claim that “observations are falling badly behind computer model predictions of what the temperature rise should be.”

    At last I can be helpful. evidence from an expert.
    ”More about Equilibrium Climate Sensitivity” earlier ATTP post
    “Andrew Dessler @AndrewDessler 14 Dec 2017
    Terrific session on climate sensitivity today at #AGU17. Lots of discussion about climate sensitivity (ECS) estimates from the 20th century. The problem is that estimates of ECS from the 20th century obs. record are lower (1.5-2°C) than models (3°C).”

    and Andrew Dessler says: April 27, 2018 at 2:51 pm
    “According to our model ensemble, 155 years is not enough to eliminate the impact of variability on the estimate of ECS. Also, you asked how internal variability could’ve turned out differently. Well, that’s exactly what our model ensemble tells us. And the answer is that it can turn out differently enough to confound our estimates of ECS.”

    …and Then There’s Physics says: April 28, 2018 at 10:42 am
    “”as Andrew Dessler indicates – if you do consider GCM results, they suggest that these observationally-based, energy-balance approaches tend to be biased low. “

  158. LOL, you have one quote noting the difference between model and observational estimates and have followed it up with two quotes casting doubt on the observational estimates not the models. Sorry angech, you should have stopped digging.

  159. Pingback: Climate Deniers pushing more emails. They've still got nothing. But the press will report on it, instead of climate change. - Red, Green, and Blue

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