Several people have written to me about today’s article in Nature by Treydte et al (including Esper) announcing that the 20th century is the wettest period in the millennium. Treydte et al state:
Comparison with other long-term precipitation reconstructions indicates a large-scale intensification of the hydrological cycle coincident with the onset of industrialization and global warming, and the unprecedented amplitude argues for a human role.
Nature published a special covering review of the Treydte article by Evans, which concurs with this as follows:
Furthermore, it seems that recent changes in precipitation patterns probably exceed the range of natural variability estimated for the past several hundred to one thousand years.
It’s hard to keep up with the extended Hockey Team, but here is a report from yr obedient servant. With the Hockey Team, nothing is ever quite what it appears on the surface and out text today provides an interesting oportunity to reflect on Soon and Baliunas, or rather the mugging of Soon and Baliunas by the Hockey Team.
Treydte et al 
Treydte et al present new analyses of dO18 values in junipers from northern Pakistan (I’ve been to this area – I heard the news of Bobby Kennedy’s assassination in Gilgit in 1968 on a shortwave radio so I can pin down the exact date that I was there.) Treydte et al:
We have evaluated precipitation changes through four, annually resolved oxygen isotope ratio (d 18O) chronologies from juniper treering cellulose (Juniperus excelsa, J. turkestanica). Three of these records cover the twentieth century and one extends back to AD 828. The latter was used to reconstruct precipitation variability over the past millennium.
They argue through correlation analyses that tree ring dO18 has a negative relationship to precipitation and a negligible relationship to temperature:
Figure 1 from Treydte et al., showing the negative correlation of dO18 with precipitation.
They then use this relationship to make a precipitation reconstruction for the past millennium, shown in the graphic below – note the inversion of the dO18 chart between figures: nothing wring with this, it’s just to visualize the inverse relationship a little better. A couple of quick thoughts on this graphic: (1) while the promotion of the Treydte et al article suggests that the the argued precipitation change is attached to anthropogenic causes, the change in level in the reconstruction (squinting at it) seems to occur in the second half of the nineteenth century and had relatively little change in the 20th century; (2) the change in precipitation level, such as it is, does not seem to consist of increased maxima in the 20th century but reduced minima i.e. fewer droughts. If the change in precipitation is caused by anthro factors and its impact in China and Pakistan has been fewer droughts in the 20th century (and I’m old enough to remember parents worrying about people starving in China), then it’s not obvious that this is a negative impact on the human race. This is not to say that further increases won’t have a negative impact, but that, if I may put it this way, the impact of global warming on net human welfare in some sense is nonlinear and non-monotonic. I.e. while Jonathan Overpeck and others predict negative and even catastrophic consequences predicted for the future – and I’m not arguing against this point here- I’m merely observing that the reduction of droughts indicated in the Treydte et al record would have to be construed as a positive consequence on any reasonable ground. That could have been observed in the Nature article, but Treydte et al didn’t seem to think it worthy of mention.
Figure 2. from Treydte et al, showing the precipitation reconstruction.
After presenting their new information, Teydte et al compare their results to other precipitation reconstructions in the following figure and it is this comparison which is used to justify the claim that "large-scale intensification of the hydrological cycle coincident with the onset of industrialization and global warming, and the unprecedented amplitude argues for a human role". I’ve bolded a couple of precipitation reconstructions which I’ll discuss below.
Original Caption to Treydte Figure 4. Precipitation reconstruction for northern Pakistan and long-term precipitation variations for different regions in the northern hemisphere. a, Tree-ring d 18O-derived reconstruction. b, Annual precipitation reconstruction (July–June) from tree-rings in northeast China . c, Southwest Asian monsoon intensity from Globigerina bulloids in the Arabian sea . d, Drought reconstruction from tree rings in western USA . e, Spring–summer precipitation reconstruction from tree-rings in southern Germany . f, Regional to hemispheric temperature variations according to ref. 11 (red, western Central Asia), ref. 4 (blue), ref. 5 (black) and ref. 8 (green). Records are normalized over their individual periods and smoothed using 150-year splines.Numbers in a–e refer to the last year of the records, and the black dashed line to the shift from negative to positive precipitation anomalies in the Karakorum record.
Soon and Baliunas 2003
Let’s turn the clock back to 2003 and consider the response by the Hockey Team to Soon and Baliunas 2003, much of which focussed on the alleged confusing of temperature and precipitation proxies. I’m not going to discuss whether Soon and Baliunas actually committed the alleged confusion; I’m also not going to talk about the use in MBH98 of actual precipitation measurements (oe even the notorious MBH98 relocation of French precipitation records to New England). I’m going to limit myself to describing policies stated by the Hockey Team in the strongest possible terms about the need to distinguish precipitation and temperature proxies. I’ll tie this together later.
Mann and a big panel of the Hockey Team led off the assault against Soon and Baliunas in EOS, saying:
In drawing inferences regarding past regional temperature changes from proxy records, it is essential to assess proxy data for actual sensitivity to past temperature variability…The existence of possible underlying dynamical relationships between temperature and hydrological variability should not be confused with the patently invalid assumption that hydrological influences can literally be equated with temperature influences in assessing past climate (e.g.,during Medieval times).
While this is not a particularly nuanced statement, Mann’s statements in public and media discussions ratcheted this up even more. Consider some of Mann’s comments about Soon and Baliunas to the U. S. Senate Committee here.
No, the work of me and my colleagues does not follow the flawed approach used by Soon and Baliunas. It is fundamentally unsound to infer past temperature changes directly from records of drought or precipitation…
numerous climate scientists have indicated (see same article) that Soon and Baliunas misinterpreted evidence of drought or precipitation as evidence of temperature changes,….
In short, the analysis by Soon and Baliunas is unsound because (a) they inappropriately interpreted indicators of past precipitation as evidence of past temperature changes, …
Drought and temperature are essentially independent climate variables. The papers by Soon and Baliunas seem not to recognize this fundamental
The Hockey Team drew a line in the sand that it was absurd to use the same record as both a temperature and precipitation proxy – again leaving aside whether Soon and Baliunas actually did this. The position taken in Mann’s Senate Committee testimony was also taken by numerous scientists in a contemporary article in the Chronicle of Higher Education. Mann’s criticisms were described in that article as follows:
It is absurd to take wetness or dryness as proof of abnormal warmth, the critics argue. " A paper using that kind of methodology could not be published in any legitimate climate-research journal unless something was severely wrong or suspicious with the review process," says Virginia’s Mr. Mann, lead author of the Eos paper, whose own studies on climate were heavily criticized by Mr. Soon’s team in the Energy and Environment paper. Mr. Soon and Ms. Baliunas improperly used data sets compiled by other researchers, says Mr. Mann. "Many people feel betrayed by the misrepresentation of their data."
The Chronicle of Higher Education article went on to report that "scientists contacted by The Chronicle complained about the way their work was cited by the Harvard-Smithsonian team." Peter deMenocal:
Peter deMenocal, an associate professor at Columbia University’s Lamont-Doherty Earth Observatory, used sediment records off the coast of Africa as a proxy for ocean-surface temperatures. He says Mr. Soon and his colleagues could not justify their conclusions that the African record showed the 20th century as being unexceptional. "My record has no business being used to address that question," the Columbia scientist says. "It displays some ignorance putting it in there to address that question."
David Black took a similar position. Note carefully here the nature of Black’s record:
David E. Black, an assistant professor of geology at the University of Akron, says Mr. Soon’s group did not use his data properly in concluding that the Middle Ages were warm and the 20th century ordinary. Mr. Black’s record of plankton in ocean sediment collected off Venezuela provides a proxy record of the strength of trade winds from 1150 to 1989. But "winds don’t meet their definition of warm, wet, or dry," he points out.
The Hockey Team mauling of Soon and Baliunas was quickly disseminated in blog world. Here’s one example from a quick google:
Meanwhile, Mann and 12 other leading climate scientists wrote a blistering critique of Soon and Baliunas’ paper in the American Geophysical Union publication Eos, noting, among other flaws, that they’d used historic precipitation records to reconstruct past temperatures”¢’¬?an approach Mann told Congress was “fundamentally unsound.”
Moberg et al 2005
Reviewers of Treydte et al 2006 would presumably be familiar with another recent multiproxy study in nature, Moberg et al 2005. If such reviewer examined the Moberg SI, he would have noted the following graphic applied as a temperature proxy.
From Moberg et al. SI
If you check the references and even compare the graphs, you’ll see immediately that Moberg et a l #11. Arabian Sea is precisely the same record as Treydte Figure 4c "Monsoon (SW Asia)", other than the Moberg record goes earlier through splicing a couple of cores. This record is not an incidental record in Moberg – it is one of the two strongest contributors to any HS-ness in Moberg. Here it should be noted that the proxy portion of Moberg is already at a knife-edge, with the MWP level just barely below 20th century benchmarks. (Such a fine distinction is very worrying to me – the first people to pick up on Enron were short traders who noted the very thin profits every year on huge capital employed. Any time you see thin differences, such as the thin differences betweeen Moberg MWP and Moberg modern, all aspects of the selection process need to be examined, which, of course, is impossible without a statement of selection criteria.)
I drew attention to the use of this record in Moberg here in February 2005 shortly after publication, pointing out:
One of the two strongest contributors to higher temperatures in Moberg’s 20th century proxies is higher incidence of subpolar glob. bulloides foraminifera in the Arabian Sea off Oman, actually a direct indicator of cooler SST.
I also discussed this proxy (together with others) here showing the extreme non-normality of this proxy – which is probably not consistent with Nature’s statistical policies, seemingly unenforced in paleoclimate.
So is the percentage of Glob. bulloides offshore Oman a temperature proxy or a precipitation proxy? Shouldn’t the Hockey Team be dumping all over either Moberg et al or Treydte et al for getting it wrong? Maybe David Black, who dumped all over Soon and Baliunas for using a wind proxy, should weigh in here. I’m having a little troble understanding why Glob. bulloides in the Caribbean should be interpreted in a fundamentally different way than in the Arabian Sea. But hey, they’re the Hockey Team.
Dulan Tree Rings
The second precipitation comparison in Treydte et al is "b. Precipitation (northeast China)". The citation, Sheppard et al., decribes a precipitation reconstruction from junipers in northeastern Qinghai. Here’s their figure 1 showing the location of the Qinghai junipers. You will notice that Dulan is on the map (also Dunde of Dunde ice cores).
Original Caption to Sheppard et al. Fig. 1 Map of People’s Republic of China (A) with the boundary of Qinghai Province. The white rectangular region B indicates an enlargement of northeastern Qinghai, where triangles indicate living treering sites, the star indicates the site with archaeological wood, the closed circle indicates the meteorological station at Dulan, and the cross indicates the Dunde ice cap (Thompson et al. 1989). The white rectangular region C is area I of moisture indices of Gong and Hameed (1991), and the region D indicates an area of Shiyang River catchment (after Chen et al. 1999, with modifications)
Alert readers will recognize that we’ve previously questioned the use of Chinese junipers as a temperature proxy on this blog. Dulan junipers were one of the important components creating modern-MWP differential in the Yang et al composite, commonly used in recent multiproxy studies (e.g. Moberg, Osborn and Briffa, Mann and Jones 2003). I discussed this last summer here, saying:
This climate-growth relationship indicates that moisture stress in growing season is a major limiting factor to tree-ring growth. This result is in general agreement with that observed in dendro-climatological studies of the same species in other areas of the Qinghai-Tibetan Plateau [Zhang and Wu, 1999; Brauning, 2001; Huang et al., 2002], suggesting that the annual growth rings mainly reflect variations in regional spring precipitation.
Yang et al. say that the junipers are correlated to autumn temperature based on Kang et al  a Chinese-language publication which is inaccessible to me. There is a later western publication, which seems to be by the same group of authors: Zhang et al, 2003.A 2,326-year tree-ring record of climate variability on the northeastern Qinghai-Tibetan Plateau, GRL, 30(14), 1739, doi:10.1029/2003GL017425
Dr. Yang posted up a comment on the above thread criticizing my statements on Dulan tree rings as follows:
About Dulan tree-ring width chronology, new width data from nearby region (Shidalong) representing winter temperature change are consistent with Dulan series usded in our paper in trend variations, giving strong evidence that Dulan chronology is an indicator of tempeature change at least.
However, the position of Sheppard et al seems to be that they are precipitation proxies. But I’m not trying to say which they are. I’m merely trying to say that they can’t be both.
In addition to their use in Yang et al, Dulan junipers under the alter ego of "Qilianshan tree rings" attributed to Wang et al 1983 were used in both Crowley and North 1991 (yes the North of the NAS panel) and Crowley and Lowery 2000. Consider the discussion here, which was applied in IPCC 2AR in 1995.
If there’s any question in your minds about whether these trees are temperature or precipitation proxies, consider the following image of a Dulan juniper from here . (I’d noticed this image a couple of years and couldn’t find it – it turned up by a google of Qilianshan Dulan)
I don’t think that you need to be dendrochronologist to think that this tree is more likely to be a precipitation proxy than a temperature proxy. But regardless of which it is, under Hockey Team policies for Soon and Baliunas, it can’t be both. If it’s a precipitation proxy (and I have no trouble accepting this view), then the use of Dulan junipers as a temperature proxy in the Yang composite (with its knock-on impact on Moberg, Osborn and Briffa, Mann and Jones etc.) or their direct use by Crowley as a temperature proxy should be condemned by the Hockey Team in terms equally as vociferous as those used to dump on Soon and Baliunas.
References: [fill in]