Jud Partin observed yesterday that a “fantastic new record” had been recently (early Nov 2008) published from Wanxiang, China. Zhang et al report that their new record is “broadly similar” to the reconstructions of Esper, Mann and Jones 2003 and Moberg as follows:
The Wanxiang record, with a d18O range of ~1.3 per mil (‰) (Fig. 1), exhibits a series of centennial to multicentennial fluctuations broadly similar to those documented in Northern Hemisphere (NH) temperature reconstructions, including the Current Warm Period (CWP), Little Ice Age (LIA), Medieval Warm Period (MWP), and Dark Age Cold Period (DACP) (5–8). [Esper, Mann and Jones; Moberg]
[Dec 4 - the following paragraphs have been revised to incorporate comments from Jud Partin below].
The data for Wanxiang (33°19′N, 105°00′E, 1200 m) was promptly archived in the paper SI. Almost concurrent with publication, another somewhat nearby speleothem from Heshang (30°27′N, 110°25′E; 294 m) was archived at WDCP, previously published in Hu et al EPSL 2007. As Jud Partin had done in 2007 with his Borneo data, the speleothem data for all three caves has been made available with commendable promptness.
The authors of Zhang et al 2008 observe in their SI, a point that needs always to be kept in mind when placing interpretations on autocorrelated data.
In interpreting such records in terms of changing climate, we are pushing the limits of these archives in terms of signal to noise ratio.
I expressed frustration the other day with the handling of the monsoon affected proxies, but didn’t entirely explain the frustration. Jud Partin observed that the orientation for the Dongge O18 record was consistent with the Wanxiang cave record (more negative dO18 up). This observation appears to me to have the corollary (though this goes beyond Jud’s specific comments) that, even if Mann’s reasons for showing the Dongge proxy more negative up originated in through data mining, the actual orientation of the Dongge O18 proxy was not objectionable.
(In defence of my prior post, I didn’t actually take a position on how these proxies should be interpreted as I’m still finding my footing with these proxies. My point was the narrower one that the Mangini orientation was not “unique” and that Gavin Schmidt’s slagging of Loehle for use of the Mangini proxy therefore required a more substantive argument. It now appears that a number of Chinese speleothem proxies have the same orientation as Mangini used.)
The other issue that I had on my mind was the opposite orientation of Socotra speleothem O18 and Dasuopu ice core O18, both monsoon proxies as well and both oriented oppositely to the Chinese speleothems. Indeed, the Dasuopu O18 record (negative dO18 down) is by far the strongest contributor to the Thompson hockey stick.
For reference, I’ve plotted five O18 series below: Socotra (from Mann data), Wanxiang, Heshang HS4, Dongge D4 and Dasuopu. All of these series are O18 series and all are monsoon records. All are oriented with negative dO18 down (this is opposite to the orientation of the Zhang et al graphic). Jud Partin pointed out below that it is customary in paleoclimate literature that “warmer and/or wetter conditions” be plotted up. For now, given the different orientations that result from the interpretations of different authors, I want to show dO18 for all series in a consistent way (saving the warmer/wetter interpretation for a second step), since, for now, I’m interested in consistency between O18. If they were all shown with negative dO18 up in accordance with the interpretation of the Chinese speleothems, it wouldn’t accord with the usual orientation of Dasuopu where more negative dO18 is interpreted as colder rather than warmer/wetter.)
Based on a visual inspection of the 5 series, I find it hard to think up a reason why the Wanxiang, Heshang and Dongge records should be oriented with negative dO18 up, while the Socotra and Dasuopu records are oriented with negative dO18 down. (I note, in passing, that the Dasuopu record has a very odd appearance relative to the well-dated speleothems. The Dasuopu ice core is in a high-accumulation area; errors in dating would increase exponentially and I’m really wondering how certain the dates of the Dasuopu ice core are, but that’s a big topic.)
Perhaps Jud or someone else can explain why some monsoon O18 records should be oriented with negative dO18 up and some with negative dO18 down. For me, such an explanation needs more than saying – Dasuopu is an ice core and Socotra is in southwest Asia not southeast Asia. I know both those things, but don’t consider these particular points to be an “explanation”.
[Dec. 5: Jud has provided a citation for the Socotra record, which I will review. He is not familiar with the Dasuopu (ice core) record. This is the one that particularly interests me, since it is so widely used and an opposite behavior is attributed to it. It's collected under quite different circumstances: by raising the issue, I am not precluding a plausible reconciliation, merely observing that it seems like something that would be nice to see in the literature.]
Hu, Chaoyong, Gideon M. Henderson, Junhua Huang, Shucheng Xie, Ying Sun, and Kathleen R. Johnson, 2008. Quantification of Holocene Asian monsoon rainfall from spatially separated cave records. Earth and Planetary Science Letters Vol. 266, No 3-4, pp. 221-232, February 2008
Zhang, Pingzhong, et al., 2008. A Test of Climate, Sun, and Culture Relationships from an 1810-Year Chinese Cave Record. Science Vol. 322, No 5903, pp. 940-942, November 7, 2008