PAGES2K, Gergis and Made-for-IPCC Journal Articles

Apr 19, 2013 – 10:36 AM

March 15, 2013 was the IPCC deadline for use in AR5 and predictably a wave of articles have been accepted. The IPCC Paleo chapter wanted a graphic on regional reconstructions and the PAGES2K group has obligingly provided the raw materials for this graphic, which will be published by Nature on April 21. Thanks to an obliging mole, I have information on the proxies used in the PAGES2K reconstructions and will report today on the Gergis reconstruction, of interest to CA readers, which lives on a zombie, walking among us as the living dead.

The PAGES2K article has its own interesting backstory. The made-for-IPCC article was submitted to Science last July on deadline eve, thereby permitting its use in the Second Draft, where it sourced a major regional paleo reconstruction graphic. The PAGES2K submission used (in a check-kited version) the Gergis reconstruction, which it cited as being “under revision” though, at the time, it had been disappeared.

The PAGES2K submission to Science appears to have been rejected as it has never appeared in Science and a corresponding article is scheduled for publication by Nature. It sounds like there is an interesting backstory here: one presumes that IPCC would have been annoyed by Science’s failure to publish the article and that there must have been considerable pressure on Nature to accept the article. Nature appears to have accepted the PAGES2K article only on IPCC deadline eve.

The new PAGES2K article contains reconstructions for all continents and has an extremely long list of proxies, some of which have been discussed before, but some only now making their first digital appearance. Each regional reconstruction is a major undertaking and deserving of separate peer review. It seems impossible that these various regional reconstructions could themselves have been thoroughly reviewed as re-submitted to Nature. Indeed, given that the PAGES2K coauthor list was very large, one also wonders where they located reviewers that were unconflicted with any of the authors.

Of particular interest to CA readers is the zombie version of the Gergis reconstruction. Previous CA articles are tagged gergis.

CA readers will recall that Gergis et al 2012 had stated that they had used detrended correlations to screen proxies – a technique that seemingly avoided the pitfalls of correlation screening. Jean S pointed out that Gergis et al had not used the stated technique and that the majority of their proxies did not pass a detrended correlation test – see CA discussion here (building on an earlier thread) reporting that only 6 of 27 proxies passed the stated significance test.

Senior author David Karoly asked coauthor Neukom to report on correlations and, after receiving Neukom’s report, wrote his coauthors conceding the validity of the criticism:

Thanks for the info on the correlations for the SR reconstructions during the 1911-90 period for detrended and full data. I think that it is much better to use the detrended data for the selection of proxies, as you can then say that you have identified the proxies that are responding to the temperature variations on interannual time scales, ie temp-sensitive proxies, without any influence from the trend over the 20th century. This is very important to be able to rebut the criticism is that you only selected proxies that show a large increase over the 20th century ie a hockey stick .

The same argument applies for the Australasian proxy selection. If the selection is done on the proxies without detrending ie the full proxy records over the 20th century, then records with strong trends will be selected and that will effectively force a hockey stick result. Then Stephen Mcintyre criticism is valid. I think that it is really important to use detrended proxy data for the selection, and then choose proxies that exceed a threshold for correlations over the calibration period for either interannual variability or decadal variability for detrended data. I would be happy for the proxy selection to be based on decadal correlations, rather than interannual correlations, but it needs to be with detrended data, in my opinion. The criticism that the selection process forces a hockey stick result will be valid if the trend is not excluded in the proxy selection step.

Unfortunately, as coauthor Neukom immediately recognized a big probleM:

we don’t have enough strong proxy data with significant correlations after detrending to get a reasonable reconstruction.

Mann and Schmidt immediately contacted Gergis and Karoly advising them to tough it out as Mann had done with his incorrect use of the contaminated portion of the Tiljander data, where Mann’s refusal to concede the error had actually increased his esteem within the climate community. Nonetheless, Gergis and Karoly notified Journal of Climate of the problem. Despite Karoly’s concerns about substantive problems, Gergis hoped to persuade Journal of Climate that the error was only in their description of methodology and to paper over the mistake. However editor Chiang’s immediate reaction was otherwise, advising Gergis:

it appears that you will have to redo the entire analysis (and which may result in different conclusions), I will also be requesting that you withdraw the paper from consideration.

Upon receiving advice from Mann, Gergis tried to persuade Journal of Climate that the error was not one of methodology, but one of language only. Bur Chief Editor Broccoli was not persuaded, responding:

In that email (dated June 7) you described it as “an unfortunate data processing error,” suggesting that you had intended to detrend the data. That would mean that the issue was not with the wording but rather with the execution of the intended methodology.

Editor Chiang added:

Given that you had further stated that “Although it was an unfortunate data processing error, it does have implications for the results of the paper,” we had further took this to mean that you were going to redo the analysis to conform to the description of the proxy selection in the paper.

After further lobbying form Gergis, Chiang reluctantly permitted Gergis to re-submit as a “revision” by the end of July, but insisted that they show the results of both methods, describing this as an “opportunity” to show the robustness of their work:

In the revision, I strongly recommend that the issue regarding the sensitivity of the climate reconstruction to the choice of proxy selection method (detrend or no detrend) be addressed. My understanding that this is what you plan to do, and this is a good opportunity to demonstrate the robustness of your conclusions.

Gergis didn’t meet the July 31 deadline and Journal of Climate reported that the paper had been “withdrawn” by the authors.

The article was apparently resubmitted to Journal of Climate by the end of September, where, according to Gergis’ current webpage, it remains “under review”.

Nonetheless, the Gergis reconstruction has already been incorporated into the PAGES2K made-for-IPCC composite. CA readers will recall the Mole Incident in 2009. Once again, I am in possession of the proxy list used in the zombie reconstruction and can report that it has had only negligible changes.

On the left is a list of the 28 proxies used in the disappeared Gergis version, highlighting the proxies re-used in the zombie version. On the right is the list of proxies in the new version, highlighting the additions. 21 of 27 proxies are re-used. Six proxies have been excluded, while seven have been added. Remarkably, Gergis has kept the numbering as close as possible to the original list, so that the first 20 re-used proxies appear in the same order as in the original table.

gergis2012-table1 cropped

gergis2013- cropped

The medieval portion of their reconstruction only has two proxies – as observed at CA very early here, where it was also pointed out that these two proxies did not constitute “new” information, as claimed in an IPCC draft, since they had not only been available for AR4 but illustrated in it.

Excluded from the original list are a tree ring series(Takapari), two ice core series (both from Vostok) and three coral series (Bali, Maiana and Fiji 1F O18), replaced by a speleothem (Avaiki), three tree ring series (Baw Baw, Celery Top West, Moa Park), two coral luminescence series (Great Barrier Reef, Havannah) and a coral O18 series (Savusavu). None of the excluded or included series is particularly long.

Obviously Gergis et al have not “redone the analysis to conform to the description of the proxy selection in the paper” as they continue to use many of the proxies that failed the original significance test – see the graphic below from last June.

Nature reviewers obviously didn’t have the concerns about robustness that were expressed by Journal of Climate editors last summer, as the new article doesn’t demonstrate any such “robustness”. It will be interesting to see whether Journal of Climate editors will themselves adhere to the scruples that they showed last summer and require Gergis et al to demonstrate the robustness of their reconstruction.

By Steve McIntyre | Posted in Uncategorized | Tagged , | Comments (55)

The Hockey Team and Reinhart-Rogoff

Apr 18, 2013 – 1:39 PM

As some readers have observed, there is a lively controversy regarding an influential recent paper by Reinhart and Rogoff. Herndon et al (of Raymond Bradley’s UMass-Amhertst) concluded that RR’s conclusions depended on a bad weighting method, inexplicable exclusion of data from certain countries and years and even an Excel coding error. All the sorts of issues that are familiar with Mann and the Hockey Team. Even the defences from Reinhart and Rogoff are eerily similar: no errors ever seem to “matter” because of some new and unfisked study. One big difference: Reinhart and Rogoff at least conceded things that were unarguable, whereas Mann and the Hockey Team concede nothing, not even things as incontrovertible as upside down use of contaminated data.

See here here here here here

. Read More »

By Steve McIntyre | Posted in Uncategorized | Comments (75)

New Nic Lewis Paper

Apr 16, 2013 – 1:49 PM

Nic Lewis’s paper on climate sensitivity is available. See his BH post here. Also see discussion at Judy Curry and WUWT.

By Steve McIntyre | Posted in Uncategorized | Tagged , | Comments (11)

Tingley and Huybers Exclude Mt Logan

Apr 14, 2013 – 1:41 PM

Perhaps the greatest single difference between being a “real climate scientist” and policies recommended here is that “real climate scientists” do not hesitate in excluding data ex post because it goes the “wrong” way, a practice that is unequivocally condemned at Climate Audit and other critical blogs which take the position that criteria have to be established ex ante: if you believe that treeline spruce ring widths or Arctic d18O ice core data is a climate proxy, then you can’t exclude (or downweight) data because it goes the “wrong” way.

This seems trivially obvious to anyone approaching this field for the first time and has been frequently commented on at critical blogs. However it is a real blind spot for real climate scientists and Tingley and Huybers are no exception.

Fisher’s Mount Logan ice core d18O series is a longstanding litmus test. It goes down in the latter part of the data and is not popular among multiproxy jockeys. Tingley and Huybers excluded Mt Logan from their data set, purporting to justify its exclusion as follows:

We exclude the Mount Logan series that is included in [35] because the original reference [36] indicates it is a proxy for precipitation source region and is out of phase with paleotemperature series.

In the figure below, I show two Arctic d18O series – on the top is Windy Dome, a Thompson series from Franz Josef Land used by Tingley and Huybers and on the bottom is the Mt Logan series that they excluded.

two ice core proxies
Top: d18O. top- Windy Dome, Franz Josef. bottom – Mt Logan.

Windy Dome d18O goes up in the 19th and 20th century. The possibility that some portion of the increase might be attributable to change in source region doesn’t cross Tingley and Huybers’ mind. On the other hand, Mt Logan goes down and the authors unhesitatingly attribute this to change in source precipitation and exclude it from their network (post hoc.)

However, they don’t consider the bias inherent in this sort of ex post exclusion. Attributing the decrease at Mt Logan to changes in precipitation source is very plausible. But it’s equally plausible and even probable that changes in precipitation sources could also work in the opposite direction, exacerbating any increase due to temperature. Perhaps there was a change in source region for Windy Dome that contributed to its recent increase in d18O values. Exclusion of Mt Logan, without a compensating exclusion of an accentuated upward series, will impart a bias to any composite.

If scientists believe that Arctic d18O is a proxy for temperature, then they cannot exclude data after the fact because it goes the “wrong” way, as Tingley and Huybers have done here. Particularly if they have no compunction about using contaminated data that goes the “right” way.

If authors take longer to report data that goes the “wrong way”, this will also bias composites at any given time. For example, Lonnie Thompson’s Bona-Churchill series, which is near Mt Logan, also goes the wrong way. Has this contributed to the delay (now exceeding 10 years) in reporting these results?

By Steve McIntyre | Posted in Uncategorized | Tagged , , , , | Comments (124)

Tingley and Huybers: Varve Compaction

Apr 14, 2013 – 10:40 AM

Specialist literature on varves e.g. Besonen et al 2008 – coauthor Raymond Bradley -(which is cited by Tingley and Huybers) make the obvious observation that varves are compacted within a core. Besonen et al 2008 allow for compaction by estimating annual mass accumulation as a more appropriate measurement of varve “thickness”, rather than uncompacted varve thickness. In their abstract, Besonen et al stated:

In many studies of lakes from the High Arctic, varve thickness is a good proxy for summer temperature and we interpret the Lower Murray Lake varves in this way. OnOn that basis, the Lower Murray Lake varve thickness record suggests that summer temperatures in recent decades were among the warmest of the last millennium, comparable with conditions that last occurred in the early twelfth and late thirteenth centuries, but estimates based on the sediment accumulation rate do not show such a recent increase

They report later in the article:

On the other hand, because of compaction, the thickness of recent varves is not directly comparable with those varves that are buried deeper in the sediment pile. This problem can be addressed by calculating a packing index (a simple ratio of the area occupied by sediment grains versus the area occupied by matrix in the varve BSE images) and then calculating the sediment accumulation rate on an annual basis (assuming a constant sediment density of 2.65 g/cm3, for quartz). This procedure compensates for compression of the sediment with depth, and results in a suppression of the trend over the last century seen in the varve thickness record (Figure 7).

An excerpt from Besonen’s Figure 7 is shown below. The top panel shows varve thickness unadjusted for compaction, while the bottom panel shows mass accumulation. The top panel (with no allowance for compaction) shows somewhat elevated 20th century levels, while the bottom panel (after allowing for compaction) does not – the phenomenon noted in their abstract.

besonen excerpt
Figure 1. Excerpt from Besonen et al Figure 7. Top – varve thickness unadjusted for compaction (but after turbidites); middle – density; bottom – mass accumulation.

A related article (Cook et al 2009 – also with Bradley as coauthor) the following year on a different Murray lake core made similar observations about compaction. Cook et al provided a temperature reconstruction using mass accumulation rate, showing a rather elevated MWP as shown below. I’m not inclined to put much weight on simplistic reconstructions from varve thickness (see also my discussion of Gifford Miller’s observations on this topic), but show this series as evidence that mass accumulation was used by this group as the relevant index.)

cook excerpt re murray lake
Figure 2. Excerpt from Cook et al 2009.

Tingley and Huybers 2013 have three classes of proxy data: MXD data, which has the familiar divergence problem; ice core O18 which doesn’t have a Hockey Stick shape and varves. The Murray Lake varve series is used. Tingley and Huybers provide an excellent SI, including exact URLs for data sets as used – a simple enough protocol that unfortunately is seldom observed. (They forgot to archive their actual reconstruction, though I presume that this is a mere oversight since their intent is clearly to provide a comprehensive archive).

In their SI, they state:

Details and references for the lake varve records used in the analysis are available in Table S.1. Unless the description of the data indicates otherwise, we use the total varve thickness.

Of the two Murray Lake versions (different cores taken by the same group), they cite the Besonen et al version.

For the Murray lake record, we use the unfiltered version of the shorter (1000 year) record posted at the NOAA Paleolimnology site [60].

However, when one compares their archive of data as used to the NOAA archive, one can immediately determine that they used varve thickness without compensating for varve compaction (the series match), rather than mass accumulation as used by Cook et al 2009 in their temperature reconstruction. This decision gives a pronounced upward bias, as shown by the difference between the two series (after taking a log and then scaling as in Tingley and Huybers.)

Murray uncompacted difference
Figure ^. Murray Lake. Difference between uncompacted varve thickness as used by Tingley and Huybers and mass accumulation. Both series logged and then scaled, before differencing.

I haven’t yet looked at how the other varve series handled compaction, but it seems like an important issue in any attempt to deduce temperatures from this sort of data. In the particular case of the Murray Lake series, it seems to me that the original data clearly “indicates” that mass accumulation be used as an index, rather than varve thickness unadjusted for compaction and that this should have been used according to the stated methodology of Tingley and Huybers.

As previously noted, Tingley and Huybers also used the contaminated portion of the Korttajarvi sediment data, so there are multiple problems with their varve reconstruction. These are not complicated issues, but ones that ought to be within the scope of even Nature peer reviewers.

By Steve McIntyre | Posted in Uncategorized | Tagged , , , | Comments (17)

New Light on Svalbard

Apr 13, 2013 – 10:59 PM

In 1997, the 121 m Lomonosovfonna ice core was drilled in Svalbard. As of mid-2009, when Hu McCulloch and I wrote CA posts on this core, nothing had been published on
O18 values prior to AD1400 nor had any Lomonosovfonna data been archived, even for the post-1400 period.

Both Hu McCulloch and I, in separate CA posts here and here, speculated that the withheld O18 values prior to AD1400 would elevated values. A digital version of the pre-1400 data became available this week in connection with Hanhijarvi et al and confirmed our surmise, as shown below. Read More »

By Steve McIntyre | Posted in Uncategorized | Tagged , , | Comments (62)

More from the Junior Birdmen

Apr 11, 2013 – 12:53 AM

A new paper in Nature by Tingley and Huybers h/t WUWT.

In keeping with the total and complete stubbornness of the paleoclimate community, they use the most famous series of Mann et al 2008: the contaminated Korttajarvi sediments, the problems with which are well known in skeptic blogs and which were reported in a comment at PNAS by Ross and I at the time. The original author, Mia Tiljander, warned against use of the modern portion of this data, as the sediments had been contaminated by modern bridgebuilding and farming. Although the defects of this series as a proxy are well known to readers of “skeptical” blogs, peer reviewers at Nature were obviously untroubled by the inclusion of this proxy in a temperature reconstruction.

tingley table s1

They stated:

For the Korttajarvi Lake record, we use the organic layer thickness, as the original publication indicates that a thicker organic layer “probably indicates a warmer summer and a relatively long growing season” [57- Boreas].

However, they didn’t mention the following:

This recent increase in thickness is due to the clay-rich varves caused by intensive cultivation in the late 20th century.

and again:

In the 20th century the Lake Korttaja¨rvi record was strongly affected by human activities. The average varve thickness is 1.2 mm from AD 1900 to 1929, 1.9 mm from AD 1930 to 1962 and 3.5 mm from AD 1963 to 1985. There are two exceptionally thick clay-silt layers caused by man. The thick layer of AD 1930 resulted from peat ditching and forest clearance (information from a local farmer in 1999) and the thick layer of AD 1967 originated due to the rebuilding of the bridge in the vicinity of the lake’s southern corner (information from the Finnish Road Administration). Varves since AD 1963 towards the present time thicken because of the higher water content in the top of the sediment column. However, the gradually increasing varve thickness during the whole 20th century probably originates from the accelerating agricultural use of the area around the lake.

All of this was discussed ad nauseam following Mann et al 2008, though Mann stubbornly refused to concede anything. Kaufman et al 2009 also used the data and, on the advice of Overpeck, conceded the point and issued a corrigendum. Raymond Bradley was a coauthor of both papers and more or less simultaneously took the position that a corrigendum was required and not required.

I’m sure that we’ll be told that their use of contaminated Korttajarvi data doesn’t “matter” – nothing ever seems to. But why use it?

Steve Update Apr 11:
 For R users, I’ve collated the Tingley proxies into a time series R-matrix called proxy.tab at http://www.climateaudit.info/data/multiproxy/tingley_2013 and their metadata as info_tingley.csv. A simple average of all the Tingley proxies is shown below. It has a divergence problem because the majority of proxies are MXD proxies.

tingley_avg

Their Figure S34 top panel shows a reconstruction from MXD proxies along. The reconstruction is very similar to an MXD average,as shown below.
mxd-recon
Figure ^. Tingley and Huybers S34 top panel, showing one variation of their proxy-only reconstructions (MXD), with average of MXD proxies (green) for comparison.

Tingley has provided an exemplary archive. It requires a little collation. R users who wish to skip their own collation may use my collation as follows:

download.file("http://www.climateaudit.info/data/multiproxy/tingley_2013/proxy.tab","d:/temp/temp",mode="wb")
load("d:/temp/temp")
tsp(proxy) #1400 2005

info=read.csv("http://www.climateaudit.info/data/multiproxy/tingley_2013/info_tingley.csv")
dim(info)	#[1] 125  11

annual=ts(apply(scale(proxy),1,mean,na.rm=T),start=1400)
count=ts(apply(!is.na(proxy),1,sum),start=1400)
max(time(count)[count>20]) #1992

#png(file="d:/climate/images/multiproxy/tingley_avg.png",w=680,h=480)
plot.ts( window(annual, end=max(time(count)[count>20]) ),ylab="SD Units")
title("Average of Normalized Tingley Proxies")
abline(h=0,lty=3)
#dev.off()
By Steve McIntyre | Posted in Uncategorized | Tagged , , | Comments (114)

The Impact of TN05-17

Apr 10, 2013 – 5:20 PM

TN05-17 is by far the most influential Southern Hemisphere core in Marcott et al 2013- it’s Marcott’s YAD061, so to speak. Its influence is much enhanced by the interaction of short-segment centering in the mid-Holocene and non-robustness in the modern period. Marcott’s SHX reconstruction becomes worthless well before the 20th century, a point that they have not yet admitted, let alone volunteered.

Marcott’s TN05-17 series is a bit of an odd duck within his dataset. It is the only ocean core in which the temperature is estimated by Modern Analogue Technique on diatoms; only one other ocean core uses Modern Antalogue Technique (MD79-257). The significance of this core was spotted early on by ^.

TN05-17 is plotted below. Rather unusually among Holocene proxies, its mid-Holocene values are very cold. Centering on 4500-5500 BP in Marcott style results in this proxy having very high anomalies in the modern period: closing at a Yamalian apparent anomaly of over 4 deg C.

TN05-17_baseFigure 1. TN05-17.

In the most recent portion of the Marcott SHX, there are 5 or fewer series, as compared to 12 in the mid-Holocene. Had the data been centered on the most recent millennium and extended back (e.g. Hansen’s reference station method is a lowbrow method), then there would have been an extreme negative contribution from TN05-17 in the mid-Holocene, but its contribution to the average would have been less (divided by 12, instead of 4). As shown below, TN05-17 pretty much by itself contributes the positive recent values of the SHX reconstruction. It’s closing anomaly (basis 4500-5500 BP) is 4.01 deg. There are 4 contributing series – so the contribution of TN05-17 to the SHX composite in 1940 is 4.01/4, more than the actual SHX value. The entire increase in the Marcott SHX from at least 1800AD on arises from increased influence of TN05-17 – the phenomenon pointed out in my post on upticks.
TN05-17 contribution
Figure 2. Contribution of TN05-17 to the Marcott SHX reconstruction.

Given the overwhelming importance of this proxy, one would like to know a little more about it. The next graphic compares TN05-17 to two other SHX proxies, also MAT proxies but from small lakes in southern New Zealand. The inconsistency of the proxies is evident. The New Zealand paleolimnological proxies have nothing resembling the mid-Holocene “cold period” that characterizes TN05-17. One thing that this graphic shows for sure: the residuals of these proxies from the “true” temperature history as translated to the respective sites do not remotely resemble a low-order AR1 process. To properly model the error distribution, one has to have an error model that permits excursions for millennia – not at all easy to specify.

SHX MAT proxies
Figure 3. Three SHX Modern Analogue Technique Proxies

It appears highly probable that there is some confounding influence on TN05-17. TN05-17 was cored in the Atlantic sector of the Southern Ocean south of Africa. As shown in the graphic below, it is located in very large scale “sediment drifts”.

agulhas drift annotated
Figure 4. Location map of TN05-17 (shown as red dot.)

Nielsen et al 2004 observed that the alkenone temperatures of the most recent samples are several degrees higher than ocean temperatures in the area. They speculated that some of the coretop might be missing – not particularly reassuring when this proxy is the most important contributor not just to 20th century SHX Marcott warming but 19th century SHX Marcott warming. There is occasional discussion in specialist literature of circumstances in which alkenone temperatures are warmer than local ocean temperatures e.g. Ruhlemann et al taking the alkenones from the warmer location in which they formed to the colder place where they settled:

We suggest that the southern samples are biased by suspended organic detritus originating from the cold subpolar waters of the northward flowing Malvinas Current, whereas the northern samples carry an UK’37 signal of tropical/
subtropical origin, transported southward with the Brazil Current. On the basis of surface ocean transport pathways and velocities simulated with the large-scale geostrophic (LSG) ocean general circulation model, we identify areas of the world ocean where alkenone temperatures are potentially biased to higher or lower values due to long particle residence times and lateral advection by surface currents.

The area studied by Ruhlemann et al was in the western South Atlantic between 30 and S. Could something similar be going in the eastern South Atlantic in the area of TN05-17 (50S, 6E) – seems entirely possible to me. There is convincing evidence that there have been secular changes in the Agulhas currents over the Holocene. The TN07-17 history certainly suggests secular changes to me: it looks like ocean currents have changed in this sector over the Holocene, such that alkenone drift (along the lines of the South American alkenone drift) has contributed to the warm values in the early Holocene and later Holocene, while colder currents were present in the mid-Holocene.

Whatever is right or wrong about Marcott et al, merely from a perspective of craftsmanship, it is not particularly reassuring that the main (Yad061 even) contribution to modern SHX warming in the Marcott reconstruction appears to arise from a “cold” mid-Holocene interval at TN05-17, translated into modern warming through short-segment mid-Holocene centering and modern proxy dropout.

By Steve McIntyre | Posted in Uncategorized | Tagged , , | Comments (38)

Alkenone Divergence offshore Iceland

Apr 10, 2013 – 10:35 AM

The longest very high-resolution alkenone core that I’m aware of is Sicre et al’s MD99-2275 (plus splices) from offshore Iceland (67N 18W). It is 4550 years long, its most recent value is 2001AD and its resolution is 4 years. Marcott used nearby core JR51GC-35 (also at 67N 18W), also an alkenone record, which had a resolution of 110 years and a most recent Marcott date of 1836AD.

Here is how the two series compare over the 4500 years covered by the Sicre et al record (originally published in 2008, but updated in 2012). (The NOAA archive is unfortunately inadequate as it does not include depth or identify splice points.)

iceland 67N 18W modern
Figure 1. 67N 18W Offshore Iceland. Comparison of Marcott et al series to high-resolution series.

Taking a longer view, here are the two series compared over the Holocene.

MD99-2275-comparison-long
Figure 2. 67N 18W Offshore Iceland. Comparison of Marcott et al series to high-resolution series.

Finally, here’s a zoom into the modern period.
iceland 67N 18W highres
Figure 3. As above. Zoom in.

In geophysical surveying, one tries to use the best quality surveys where available and benchmark lower quality surveys against the highest quality ones. If this methodology were used here, the errors in JR51GC-35 are obviously very large, much higher than arising from the alkenone calibration equation by itself, though other factors could be at work as well.

MD99-2275 has well-dated core going deep into the Holocene. Hopefully, Sicre and other specialists will continue their commendable program. Seeing if these results can be replicated in another core would also do much to increase confidence.

The alkenone divergence problem is clearly present in this data. ALkenone-estimated temperatures in the 20th century continued to decline. In the Marcott reconstruction, JR51GC-35 makes its last (very negative) contribution in the 1820 step. By the act of no longer participating, it causes the Marcott composite to go up in the next period, even though it appears that the “true” alkenone estimated temperature in the area continues to decline.

Postscript: I mentioned MD99-2275 as a high-resolution core in my notes on AGU 2006. Like McGregor’s Cape Ghir (used inverted), it was one of the proxies in Trouet et al 2009 discussed at CA here. Here is a figure showing the updated Sicre version against the Trouet et al illustration. The Sicre version is in cyan (versus the “Iceland” series in blue). The divergence in the present series continues further than in the Trouet version.

trouet-2009-annotated
Figure 4. Excerpt from Trouet et al 2009, showing updated Sicre et al series.

By Steve McIntyre | Posted in Uncategorized | Tagged , , | Comments (17)

Alkenone Divergence in Peru

Apr 9, 2013 – 6:03 PM

Gutierrez et al (GRL 2011) pdf here; data here is another very high resolution alkenone series that is well-dated in the 20th century. It was taken in an upwelling zone offshore Peru at a similar latitude to Quelccaya.

Like the high-resolution series offshore Morocco and Namibia, it shows a sharp decline in alkenone-estimated SST in the 20th century, as illustated below. (The archived data has a little more coverage -back to ~1750.)

B0406 alkenone
Excerpt from Gutierrez at al 2011.

The authors survey temperature data at nearby stations (Callao, Pisco and a few others) and report slight cooling in the late 20th century. They suggest “ERA 40 reanalysis indicates its link [cooling] with intensified alongshore winds driving upwelling in spring”.

The closest Marcott proxy is GeoB7139-2, taken offshore Chile at approximately 30S. (A closer comparison would be nice.) This proxy is shown below. It only has two radiocarbon dates in the entire Holocene and only has resolution of ~520 years. (Stated data selection criteria are that “at least four age-control points span or closely bracket the full measured interval” and “sampling resolution is typically better than ~300 yr”.

GeoB7139-2
Figure 2. GeoB 7139-2 per Marcott.

The next graphic shows GeoB7139-2 together with B0604 (the latter offset by 4 deg C).
B06045 comparison
Figure 3. B0604 (offset 4 deg C) and GeoB7139-2.

Although we’ve been reassured by Marcott apologists of the ability of their data and method to capture any past upspike, one feels that this particular series will not be much help in that enterprise.

In Lonnie Thompson’s recent Quelccaya publication, Thompson estimated Nino3-4 SST. Needless to say, they don’t bear much similarity to the alkenone SSTs shown here.

Stepping back from Marcott, increased upwelling in the late 20th century seems to have occurred all over the globe. In addition to the upwelling sites surveyed here in the last couple of days (Morocco, Namibia, Peru), I’ve also seen 20th century declines in alkenone data offshore Iceland and, of course, in the two Marcott series where the decline was deleted: MD03-2421 offshore Japan and OCE326-GGC offshore eastern Canada, both of which I’ll now reconsider with this in mind.

By Steve McIntyre | Posted in Uncategorized | Tagged , , , , | Comments (35)
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