There was some publicity this week on a paper by Young et al (Science Advances, 2015), which, according to Gifford Miller , whose work has been frequently discussed at CA (see tag), had supposedly put the “coup de grace on the Medieval Warm Period”, that had been so long wished for by the Team. I will discuss (and dissect) this article in a forthcoming post, but first wish to report on some related developments in an article (Balascio et al, Climate of the Past, 2015) which I had discussed last summer while it was in open review, which I will subsequently connect to the discussion of Young et al.
Balascio et al (coauthor Raymond Bradley) had reported the (amazingly) strong similarity between the varve thickness series at Hvitarvatn, Iceland (Miller et al 2012) – see panel D below – and at Big Round Lake, Baffin Island (Thomas and Briner, 2009) -see Panel B below. This similarity was originally reported at Climate Audit in 2012 and subsequently discussed in many Climate Audit articles, including the Climate Audit criticism of PAGES2K’s upside-down use of the Hvitarvatn series, a criticism that was subsequently plagiarized by Darrel Kaufman and Nick McKay (Nature Climate Change, 2014).
The Balascio et al 2015 figure showing the similarity (shown as an excerpt below) is unchanged from the article submitted for open review.
Figure 1. Excerpt from Balascio et al, 2015 Figure 5. Original caption: … (b) Big Round Lake, Baffin Island, varve thickness and magnetic susceptibility (Thomas and Briner, 2009; Thomas et al., 2010). (c) Baffin Island ice cap activity reconstructed using vegetation kill dates with text showing original interpretations (Miller et al., 2012). (d) Langjökull ice cap, Iceland-based on varve thickness from Lake Hvítárvatn (Larsen et al., 2011). Blue shading marks periods of increased glacier size (sustained above average PC1 values).
For reference, here is the figure that I had used in my comparison of these two series in February 2012.
Figure 2. Varve thickness (mm). Purple – Hvítárvatn from Miller et al 2012 Figure 2D; blue – Big Round Lake (NCDC sheet 7 column 4) 30-year running mean. Both shown on same mm scale.
However, in the open review article, Balascio et al did not confront the opposite interpretations of the varve data by Miller et al and by Thomas and Briner. Miller et al had (plausibly) interpreted thick varves as evidence of glacier proximity – see CA here for support of this interpretation from IRD (ice-rafted debris) data, while Thomas and Briner 2009 (followed by numerous multiproxy authors including PAGES2K) interpreted thick varves as evidence of warming. This created an inconsistency for PAGES2K, which originally used Hvitarvatn varve data upside-down to Miller’s interpretation – an assumption sharply criticized at Climate Audit here.
A year later, PAGES2K lead author Darrell Kaufman, in in McKay and Kaufman 2014, acknowledged that the Hvitarvan data had been used upside-down in PAGES2K, but did not credit (i.e. plagiarized) Climate Audit -see CA discussion here. Kaufman also refused to issue a corrigendum to the erroneous PAGES2K reconstruction, which remains widely used. As I observed at the time, PAGES2K’s correction of Hvitarvatn resulted in the ironic situation that they now used the very similar Hvitarvatn and Big Round Lake series in opposite orientations.
In the original (open review) version of Balascio et al 2015 (discussed at CA here), Balascio and coauthors presented the similarity of the Hvitarvatn and Big Round series, but did not discuss the inconsistency latent in the academic literature, as follows:
Varve thickness and magnetic susceptibility data from a proglacial lake [Big Round Lake] on Baffin Island, if interpreted to reflect glacier size, also reveal two similar distinct glacier advances at these times (Fig. 4) as well as the earlier advance ca. AD 1250–1300 also observed in the Kulusuk record (Thomas and Briner, 2009; Thomas et al., 2010).
In the final version, Balascio et al were aware of the inconsistency, but refused to grasp the nettle to comment on the inconsistency. First, they modified the above sentence to only refer to magnetic susceptibility:
Magnetic susceptibility trends, linked to glacier size changes, from another high-resolution proglacial lake record on Baffin Island (Big Round Lake) reveal two similar distinct glacier advances at these times (Fig. 5) as well as an earlier advance ca. AD 1250-1300, which is also observed in the Kulusuk record (Thomas et al., 2010).
They then observe (as I had commented at CA on numerous occasions) that varve thickness at Big Round Lake, Baffin Island has been “previously interpreted” as a proxy for warmth, rather than glacier proximity, but refused to grasp the nettle. Rather than requiring consistency of interpretation, they airily speculated that the opposite interpretations could be saved, if the opposite interpretations “can possibly be attributed” to “different sedimentary processes operating over different timescales”. They evaded reconciliation by saying that they “cannot account for this apparent contradiction without further analysis of those records”:
However, varve thickness data from Big Round Lake, which has previously been interpreted to represent summer temperature, resemble trends in magnetic susceptibility (Thomas and Briner, 2009). This discrepancy can possibly be attributed to how the two proxies track different sedimentary processes operating over different timescales (annual vs. centennial), but without further analysis of those records we cannot account for this apparent contradiction.
The referees did not require them to carry out the “further analysis”. But why not? This is a fundamental discrepancy between important proxies that Balascio et al had themselves cited in their article. And if not now, when?
Thus, despite the obvious and striking coherence of the varve thickness data between Iceland and Baffin Island – one of the most striking similarities in the entire field, Balascio et al only cited magnetic susceptibility as support for “regionally coherent cooling phases” in the North Atlantic from Baffin Island to Greenland and to Iceland (when the coherence between varve thickness series was, in my opinion, even more impressive):
We argue that the magnetic susceptibility data from Big Round Lake are consistent with other data from around Greenland, indicating that the most extensive glacier advances since the early Holocene occurred between AD 1250 and 1900, and provide evidence for regionally coherent cooling phases during the Little Ice Age (Grove, 2001).
It’s too bad that Balascio et al didn’t confront the obvious answer: the astonishing similarity between the varve thickness series at Hvitarvatn, Iceland and Big Round Lake, Baffin Island – both in the North Atlantic and both proximate to glaciers with appreciable Little Ice Age variation – points to “regionally coherent” changes and the need to interpret both series consistently. The inconsistency between interpretations of the Hvitarvatn and Big Round Lake series remains a rebuke to the “community”.
Even aside from its similarity to Hvitarvatn, the “community” interpretation of Big Round Lake makes no sense. Under the Thomas and Briner interpretation, the 19th century appears as the “warmest” time in the past millennium, when we know that IRD (ice-rafted debris) re-occurred for virtually the first time since the LGM. Under the Thomas and Briner interpretation, Baffin Island supposed experienced a Medieval Cold Period and Little Warm Age – a history that is directly contracted by other indicators, not least of which are Miller’s radiocarbon dates for moss killed by ice cap expansion (panel C in first figure above.)
The community reticence in calling out the incorrect interpretation of Big Round Lake series may very well come from its widespread use in IPCC multiproxy studies, including the Ljungqvist variations: Kaufman et al 2009, Ljungqvist 2010, Christiansen and Ljungqvist 2011, Christiansen and Ljungqvist 2012, Ljungqvist etl 2012, Shi et al 2013, Tingley and Huybers 2014, PAGES2K – see CA here. Flipping the Hvitarvatn series had a dramatic impact on the PAGES2K Arctic reconstruction; while flipping the Big Round Lake series would not have as much impact, it would impact medieval-modern comparisons.
Also, if the community were to admit an error on Big Round Lake, then this would require re-examination of the numerous other varve thickness series that are a staple of the IPCC AR5 millennium spaghetti graph.
McKay and Kaufman, 2014. http://www.nature.com/articles/sdata201426.pdf
Balascio et al 2015 (CPD) http://www.clim-past-discuss.net/11/2009/2015/cpd-11-2009-2015.html