Over at Climate Audit, Steve McIntyre has found yet another unexplainable inclusion of a hockey stick shaped proxy in the PAGES2K paper. What is most interesting about it is that when you look at the proxy plot panel, it reminds you of the panel that Steve plotted for Yamal, where just one proxy sample went off the rails as an apparent outlier and seems to dominate the set. Since even a grade school student could pick this proxy out in one of those “which one of these is not like the others?” type test questions, one wonders if this particular proxy was preselected by Kaufman specifically for its shape, or if they just bungled the most basic of quality control inspections. Of course, when Steve asked those questions, Nick Stokes showed up to defend the indefensible, and hilarity ensued.

Steve McIntyre writes:

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Kaufman and paleo peer reviewers ought to be aware that the recent portion of varve data can be contaminated by modern agriculture, as this was a contentious issue in relation to Mann et al 2008 (Upside Down Mann) and Kaufman et al 2009. Nonetheless, Kaufman et al 2013 (PAGES), despite dozens of coauthors and peer review at the two most prominent science journals, committed precisely the same mistake as his earlier article, though the location of the contaminated data is different.

The contaminated series is readily identified as an outlier through a simple inspection of the data. The evidence of contamination by recent agriculture in the specialist articles is completely unequivocal. This sort of mistake shouldn’t be that hard to spot even for real climate scientists.

Here is a plot of the last nine (of 22) Arctic sediment series. One of these series (top left – Igaliku) has the classic shape of the contaminated Finnish sediment series (often described as upside down Tiljander). Any proper data analyst plots data and inspects outliers, especially ones that overly contribute to the expected answer. The Igaliku series demands further inspection under routine data analysis.

Figure 1. Plot of last nine (of 22) Kaufman et al Arctic sediment series. The Igaliku proxy is total pollen accumulation.

The Igaliku series is plotted separately below. It is also available at a NOAA archive here , which actually contains one additional recent value plotted in red. The NOAA archive contains many other measurements: it is unclear why Kaufman selected pollen accumulation rate out of all the available measurements.

The resolution of the data set is only 56 years (coarser than the stated minimum of 50 years) and only has three values in the 20th century. The value in 1916 was lower than late medieval values, but had dramatically surged in the late part of the 20th century.

Figure 2. PAGES2K Igaliku series.

Igaliku is in Greenland and was the location of the Norse settlement founded by Erik the Red and is of archaeological interest. Sediment series from Lake Igaliku have been described in three specialist publications in 2012:

Massa et al, 2012. Journal of Paleolimnology, A multiproxy evaluation of Holocene environmental change from Lake Igaliku, South Greenland. (Not presently online) . (Update: online here h/t Mosher. I’ve added a paragraph from this text referring to pollen accumulation.)

Massa et al 2012. QSR. A 2500 year record of natural and anthropogenic soil erosion in South Greenland. Online here.

Perren et al 2012, 2012. Holocene. A paleoecological perspective on 1450 years of human impacts from a lake in southern Greenland. Online here.

The three articles clearly demonstrate that the sediments are contaminated as climate proxies.

Igaliku has been re-settled in the 20th century and modern agricultural practices have been introduced. The specialist publications make it overwhelmingly clear that modern agriculture has resulted in dramatic changes to the sediments, rendering the recent portion of the Igaliku series unusable as a climate proxy. Here are some quotes from the original article.

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Read Steve’s entire essay here: More Kaufman Contamination

Nick showed up to argue that the Igaliku really isn’t contaminated by agriculture at all, and is currently engaged in an multi-front battle of deny, duck, and cover. The obstinance on display to prevent admitting the obvious is diamond hard. This isn’t unusual, as Nick was associated with CSIRO, where admissions aren’t part of the government funded manual. Gadflies and racehorse comparisons were bandied about and now Steve has taken to calling Nick “racehorse” much in the same vein as Tamino and his self proclaimed “bulldog” status.

To say watching this is entertaining, would be an understatement. Meanwhile there have been many updates and piling on of additional evidence for contamination. Nick is now reduced to rebutting Steve with Bill Clinton style questions (“It depends on what the meaning of the words ‘is’ is.”) such as: “Could you say exactly what you mean by “contaminated core”?”

Here is my contribution that I left as comments:

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Anthony Watts Posted Apr 30, 2013 at 12:09 AM

Steve writes:

The three articles clearly demonstrate that the sediments are contaminated as climate proxies. Igaliku has been re-settled in the 20th century and modern agricultural practices have been introduced.

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By way of support for this, photos can tell you a lot.

Google Earth’s aerial view clearly shows the developed agriculture signature:

And from the ground, hay bales in Igaliku from the Wikipedia page on Igaliku:

The slope of the land drains right into the lake, and along the slope is clearly human agricultural development.

O’Rourke and SOlomon 1976 have recently found that total pollen influx was a direct function of sediment influx in varved sediments from seneca Lake, New York.

Given the drainage pattern of the land, it seems like a clear case of sediment contamination to me.

Kaufman has followed his rules, which are to use proxies which: “(5) exhibit a documented temperature signal, and (6) are published in peer-reviewed literature as a proxy for temperature”

One wonders though if Igaliku wasn’t preselected due to the shape of the data without any other considerations.

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Note: the Google Earth image is of the town near the fjord, the Wikipedia picture of the lake where sediment was sampled is in the highland just to the NW of the town. You can inspect the map here and see the lake (which is ice-covered in the satellite photo):

http://maps.google.com/maps?q=60.987778,-45.420833&ll=61.009153,-45.439453&spn=0.053414,0.185394&t=h&z=13

Update: here is another view of the lake from the ground, showing agriculture all around the catch basin, thanks to Nick and anonymoose http://www.panoramio.com/photo/12426959

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Bishop Hill might like the Bishops proxy, but Mosher added the real clincher though:

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Steve Mosher Posted Apr 29, 2013 at 2:39 PM

http://www.academia.edu/2367255/A_multiproxy_evaluation_of_Holocene_environmental_change_from_Lake_Igaliku_South_Greenland_of_environmental_change_from_Lake_Igaliku_South_Greenland._Massa_C._Perren_B._Gauthier_E._Bichet_V._Petit_Ch._Richard_H

“Norse farmers settled southern Greenland *985 AD(Jones1986) including the area around Lake Igaliku,which was used for grazing and hay production.Following the disappearance of the Norse *1450 AD,Igaliku was resettled during the 18th century (Arne-borg2007) and large-scale agriculture, based on sheep farming, was developed in the 1920s (Austrheim et al.2008). Consequently, the response to climate changeover the last millennium was overprinted by land-use effects (Gauthier et al.2010; Massa et al.2012; Perrenet al.2012). However, the consideration of human-induced changes at Lake Igaliku in light of the entire Holocene ecosystem development provides new insights about their magnitude.Relative to the preceding Holocene shifts, the vegetation was slightly impacted by land clearanceand grazing, and exhibits a small decrease in woodytaxa abundance (from 60 to 45 %). Until *1335 AD,the related soil erosion, documented by high TOC/TNand MAR values, clearly compounds the long-termincreasing trend (Fig.6). Contrary to the other studiedvariables, the diatom assemblages indicate that thelake ecology was not signiﬁcantly impacted, and that the changes are within the range of natural Holocene variability.Both in terms of lake ecology and soil erosion, theperiod since 1988 AD is likewise unprecedented in the context of the Holocene by a magnitude and rate of change greater than the previous 9,500 years. The digging of drainage ditches for hayﬁelds caused adramatic increase in MAR, which reached unprece-dented values. The use of nitrogen fertilizers on theseﬁelds (200–250 kg ha -1 yr -1of N, Miki Egede pers.commun.) have outpaced the natural buffering capac-ity of Lake Igaliku, resulting in a sharp rise in themesotrophic diatom, Fragilaria tene

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Nick, in classic Mannian style, refuses to concede. Go help him out at the Climate Audit thread More Kaufman Contamination which is sure to become a classic.

This Stokes-Kaufman incident seems to be a case of land use effect denial.

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