You’d think academics in the upside down Mann climate proxy world would pay attention, and not repeat the same mistakes of the past. Apparently not. WUWT readers surely recall the Yamal YAD06 (The most influential tree in the world) and the core sample YAD061.
Steve McIntyre points out the YAD061 equivalent in Marcott et al, where a single sample contributed the majority of the uptick.
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.
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.
Read the entire post here: http://climateaudit.org/2013/04/10/the-impact-of-tn05-17/