Richey et al 2007 and Cariaco

A recent study, Richey et al 2007, showed a warm MWP in the Pigmy Basin, Gulf of Mexico. Julie Richey made an effective presentation at the AGU Session showing an elevated MWP from her foram studies and, together with Alicia Newton who made a similar presentation, had Mann gnashing his teeth. In a chat afterwards, Richey said that they had faced unusual opposition from one reviewer who threw many roadblocks towards publishing their results – something that was unprecedented in their experience in presenting empirical results from a qualified laboratory. Richey’s results were recently mentioned by poster at Tamino, causing Tamino (an interesting writer when he’s calm) to have one of his all-too-frequent temper tantrums, saying that he wasn’t interested in regional results, although he seems all too content to rely on composites of small numbers of much more flawed data (e.g. Moberg’s dependence on the much more questionable Arabian Sea G Bulloides series.)

I thought that it would be interesting to compare her results (also promptly archived both at the journal and at WDCP) to David Black’s Cariaco results. In a way, you’d like to see this sort of comparison in the original articles. Black discusses comparisons between the Cariaco results and 4 or 5 other series, but doesn’t illustrate them. I understand the space limitations of journals and don’t fault Black for not illustrating the comparisons, but nonetheless I think that doing some of these comparisons not done in the articles is a useful form of perspective. Note that it depends on prompt archiving of data. It’s really nice to read one of these articles, look for relevant comparanda and be able to get a perspective on them in an hour or two without months of quasi-litigation as in Hockey Team World (Mann-Bradley-Hughes-Briffa-Jones-Esper).

I’m going to show both dO18 and Mg-CA, showing the dO18 comparison first (also showing in this case Keigwin’s Sargasso Sea results.) The most obvious difference between these series is the difference in texture. The varved Cariaco series with annual to near-annual resolution has much higher resolution than the decadally resolved Pigmy Basin Basin series, which in turn is much more highly resolved than the relatively early (!996) Keigwin Sargasso Sea series, that is often used by people wanting to show an MWP (we used it in our presentation to NAS showing that, by “apple-picking”, you could get an MWP warmer than modern proxies that, in our opinion, was neither more or less convincing that cherry-picking results selecting series to show modern proxies higher than MWP.)

Can one then locate a “signal”? Here you see why paleoclimatologists work so hard to extract patterns from tree rings where, at least, you can have confidence in your dates. If you allow for dilation of the age scale in the Pigmy Basin series (which assumes a constant sedimentation rate from radiocarbon – fair enough as an assumption but which will dilate the scale if sedimentation rates vary as they undoubtedly have), I can persuade myself right now that the 1400-1800 pattern in the Pigmy Basin more or less matches the 1450-1800 pattern in the red Cariaco series, so that the signal is enhanced if the dates of Pigmy Basin are tuned to Cariaco. But maybe the dates are right and there are regional differences in signal. Without tuning, the Pigmy Basin series is completely uncorrelated to the smoothed G Bulloides dO18 series (r=0.00), but the smoothed G Bulloides dO18 series has a low correlation to the smoothed G Ruber series (0.06) as well. The Richey series has a correlation of 0.20 to the smoother Cariaco ruber series. Here’s the graphic – some more comments after the graphic.

cariac39.gif

The modern comparisons are also rather interesting. Black et al 2004, which discussed these results, presented two very different possible explanations for their dO18 results:

First, the increase in d18O may indicate that tropical summer-fall SSTs have cooled by as much as 2 deg C over the last 2000 years, possibly as a result of a long-term increase in upwelling intensity. Alternately, comparisons to other studies of ITCZ and regional evaporation/precipitation variability suggest that much of the d18O record is influenced by decadal- to centennial-scale variations in the mean annual position of the ITCZ and associated rainfall patterns.

The Pigmy Basin results, while not as resolved, like Cariaco, show “cold” results through the 19th century, with a 20th century increase. One feels that there is some information here, but it’s hard to say what it means.

Both Black and Richey also present Mg-Ca results – a relative new technique that is said to be less confounded by precipitation. I showed a graphic of Black’s temperature reconstruction the other day; here’s it is compared to the Richey reconstruction. Again one can persuade myself that there is some similarity between the series – one’s eye wants to de-align the Richey series a little, tuning it to the Cariaco series: is such tuning justified given the known dating imprecision of the Pigmy Basin series? And what are the statistical implications of such tuning? Not easy questions. If you tune the Richey series to Cariaco, it seems to me that this will bring the warm “MWP” portion of her series a little closer to the present, probably moving it to cover the 11th century known to be warm in northern Europe. (Without tuning, the correlation between the Richey series and the smoothed Cariaco series is 0.15).

One obvious difference between the two series is their core top dating. Richey’s series ends at 0 BP (thus 1950 AD) while Black’s comes to 1990 AD. Richey’s data is more or less decadally resolved and the wiggle match to Cariaco is definitely improved if the core top on her series is dated much closer to the end of Black’s series. Can this be justified? It doesn’t seem inconsistent with the evidence.

cariac34.gif

On the other hand, if you don’t tune, you quickly lose any sense of regional pattern. One series goes down while another is going up. In IPCC AR4, they show a bunch of series like this and say – aha, there’s no MWP. While this is possible, you could also get a dog’s breakfast if you have variable dating imprecisions – a point that Craig Loehle has argued for a number of years, but not mentioned by IPCC. The cases shown here are relatively clean examples of the problem – do you tune or not. And if there is no common signal at this resolution between such similar proxies, what hope is there for extracting a common signal from small populations (10-12 series) of proxies in a typical Team study.

I received some information yesterday from David Lund and William Curry on their sediment studies in the Dry Tortugas and Bahamas, which I will try to compare to this next week. When I inquired to William Curry, he responded promptly, expressing some surprise that the data had not been posted up at WDCP and immediately arranged for Lund to send me the data which he did a few hours later, together with a very cordial invitation to telephone him with any questions – a far cry from the typical quasi-litigation with the Hockey Team for scraps of data. The oceanographers seem to be a very cooperative group – I’ve had very prompt and friendly responses from Lowell Stott, Julie Richey and Alicia Newton as well.

17 Comments

  1. Larry
    Posted Nov 1, 2007 at 9:14 AM | Permalink | Reply

    What’s the bunny got to say about the “European warm period” in the gulf? Took a wrong turn in Albekoiky?

  2. Gary
    Posted Nov 1, 2007 at 9:42 AM | Permalink | Reply

    Some thoughts on tuning:

    1. With only two or three curves that are C14-dated at only a couple of points, you match peaks and valleys and hope for the best. Graphical correlations as shown here make it a little better and can reveal something about changing sedimentations rates.

    2. Another approach is to do a spectral analysis of the curves and try to tune the points between the C14 pegs so that cycles are more distinct and coherency is improved.

    3. Then there is always analyzing more curves at both sites (CaCO2, species abundance frequencies for forams, radiolaria, diatoms, etc.) for comparable features using techniques in 1 and 2. All it takes is some extra lab work.

  3. Steve McIntyre
    Posted Nov 1, 2007 at 9:52 AM | Permalink | Reply

    #3. In fairness, these studies are both hot off the press and the development of high-resolution ocean sediment studies is very new – and something that I think has considerable potential for shedding light on climate of the past millennium – and perhaps even ultimately shedding some light on tree ring records.

  4. MarkW
    Posted Nov 1, 2007 at 9:53 AM | Permalink | Reply

    http://www.co2science.org/scripts/CO2ScienceB2C/subject/m/subject_m.jsp

    Has a bunch of papers showing the existence of the MWP from all over the world.

    junkscience.com also has a weekly feature highlighting a new MWP paper.

    It looks like the team is the only group still wedded to the notion that the MWP was a European only feature.

  5. Gary
    Posted Nov 1, 2007 at 10:26 AM | Permalink | Reply

    #4. No criticism of the studies was intended. I was offering suggestions on how to improve the tuning based on successes with lower sed rate cores. It’s great to see the data appear and to have it made available freely. I’ve long thought varved sediments in anoxic basins were gold mines begging to be explored.

  6. Steve McIntyre
    Posted Nov 1, 2007 at 10:30 AM | Permalink | Reply

    #5. While the citations there are an interesting bibliography, if that was put forward as the documentation for a “consensus” establishing an opposite point of view, I’d be just as critical of it. I think that my time is better allocated towards consideration of the viewpoints adopted by major institutions and my time is finite.

  7. Steve McIntyre
    Posted Nov 1, 2007 at 10:48 AM | Permalink | Reply

    I experimented with dating the Richey Mg-Ca series more recently in 1-year steps and then comparing correlations to a smoothed Cariaco Mg-Ca. Dating the end of the Richey series 40-45 years later (it is dated 0 BP) improves the correlation.

    Annoyingly neither of the original articles actually says when either core was drilled. Googling a PhD Thesis here, says that the Pigmy Basin core was drilled in 2002.

    Core MD02-2553 was taken from the basin center in 2002 during IMAGES cruise VIII (PAGE). The giant box core is 10.3 m long and a continuous sub-sample was obtained with U-channels. The U-channels used were designed and developed at the Paleomagnetism and Environmental Magnetism laboratory of the LSCE, Gif-sur-Yvette. Box core PBBC-1 was taken on the RV Longhorn at approximately the same location as the giant box core.

    For dating, Richey says:

    [they used] a core-top age of 0 yr B.P. The youngest radiocarbon date indicates a post-A.D. 1950 age for the upper 2 cm of core PBBC-1; therefore we infer that the data from the core top in our record represent near-modern conditions.

    I haven’t located exactly when the core PL07-71 (and PL07-73) were taken. Black says:

    We sampled sediments from a box core (PL07-71 BC; 1045.460N, 6441.860W, 395 m water depth) and a gravity core (CAR7-2; 1039.060N, 6439.60 W, 449 m water depth) recovered from the gentle northeastern slope of the Cariaco Basin.

    and ascribes a date of 1990 to the most recent varve. So it was presumably drilled around 1991.

    Given that Richey’s core was drilled about 11 years later and has decadal resolution, it seems pretty logical to bring its most recent decade to the 1990s consistend with Black, rather than using 0 BP as 1950. In fairness to Richey, she didn’t convert dates to calendar years, so it’s not as though she particularly turned her mind to this particular matter. Nonetheless, she didnt use -40 BP as she might well have done.

  8. MarkW
    Posted Nov 1, 2007 at 10:53 AM | Permalink | Reply

    1) I don’t see where I requested that you audit any, much less all of the studies listed at co2science.
    2) While the existence of such an archive is not sufficient to prove that there is a consensus that the MWP was world wide, it is sufficient to disprove the team’s claim that the MWP was a European only phenomena.

  9. richardT
    Posted Nov 1, 2007 at 10:54 AM | Permalink | Reply

    #7
    Setting the top of the core to 0BP is quite common, and makes sense if it can not be guaranteed that the sediment water interface was retrieved, and are more interested in centennial than decadal variability.

  10. Gary
    Posted Nov 1, 2007 at 11:58 AM | Permalink | Reply

    #6. I’m sensing that somehow my posts are being taken as opposition or challenge. Not so at all. I think you’re doing great work with CA and my comments are only meant to add to the conversation. Have I unwittingly done something offensive?

  11. MarkW
    Posted Nov 1, 2007 at 12:07 PM | Permalink | Reply

    Gary,

    My post was originally #5, a deleted post caused a numbering decrement.

  12. Dave Dardinger
    Posted Nov 1, 2007 at 2:11 PM | Permalink | Reply

    re: #10 Gary,

    I think it’s more that Steve doesn’t want to align himself with most of the existing skeptic sites as warmers use references to the Idsos or Junk Science as too political and discount the person making the references. Frankly I think it’s just another way for warmers to avoid having to engage in level-playing-field debate.

    In the case of the Idsos, they often draw different conclusions from a paper than the author does, so the warmer trick is to get one or more of the authors to make a statement saying that they (the Idsos) are wrong, generally without having to justify the statement scientifically, and then use that as a reason not to have to consider further anything they say. Steve should recoginize the trick as it’s been used against him too, but I guess he’d rather not have to justify anything he wasn’t directly involved in. Can’t blame him for that.

  13. Jeremy Friesen
    Posted Nov 1, 2007 at 3:08 PM | Permalink | Reply

    you could also get a dog’s breakfast

    Am I too young to get this reference/lingo?

  14. Steve McIntyre
    Posted Nov 1, 2007 at 3:17 PM | Permalink | Reply

    #13. I guess so – it just means a mess. I didn’t think about it being age-specific slang. But you don’t hear bee’s knees any more.

  15. Paul Linsay
    Posted Nov 1, 2007 at 3:24 PM | Permalink | Reply

    #13

    As a dog returneth to his vomit, so a fool returneth to his folly.

    –Proverbs 26:11

  16. Gary
    Posted Nov 3, 2007 at 8:08 PM | Permalink | Reply

    #11 – MarkW, thanks for the explanation. I hate when that happens.

  17. SteveSadlov
    Posted Jan 11, 2008 at 8:56 PM | Permalink | Reply

    Over at “Bunny Hutch Headquarters”

    http://rabett.blogspot.com/2008/01/elevator-trouble-simon-donner-at-maribo.html#links

2 Trackbacks

  1. [...] only the anthropogenic global warming data looked half this convincing….  ..bruce [...]

  2. By The Trouet Ocean Proxies « Climate Audit on Sep 11, 2010 at 10:33 AM

    [...] used as evidence of an MWP. It is digitally available online. A detailed discussion at CA here here [...]

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