IPCC AR4 is online – thanks to readers for pointing this out. I didn’t notice any press releases or hoopla. The lead author for the millennial paleoclimate section was Keith Briffa, who takes a realclimate line on the debate – surprise, surprise. Their comments on M&M are pretty much the same as in the Second Draft – they essentially disregarded the comments by Ross and myself, even on what we are supposed to have said. The Team features prominently in the chapter – a search on Mann turns up 92 mentions; Briffa 36 mentions; Jones 36 mentions;
Like Mann before him, Briffa used his position as Lead Author to publicize his own work – I don’t know whether this sort of behavior is prevalent in other chapters, but it’s something that is a risk when authors are parties to controversy, something that I and others (von Storch) criticized in the past. The spaghetti graph in Box 6.4 of Chapter 6 here is taken from the series in Osborn and Briffa 2006. Curiously, although these are exactly the series in Osborn and Briffa 2006, they do not mention this article, instead attributing the series to “proxy records collated from those used by Mann and Jones (2003), Esper et al. (2002) and Luckman and Wilson (2005)”. If you look closely at the right hand side and I’ll discuss this further, you can see a few proxy-series that peak in mid-century and close at low levels (the Divergence Problem) and a few that close at high values – the high closers are Mann’s PC1 – which, despite all the publicity, reappears here bold as brass, a foxtail series and Yamal, like aged streetwalkers with too much mascara.
Box 6.4, Figure 1. The heterogeneous nature of climate during the Medieval Warm Period’ is illustrated by the wide spread of values exhibited by the individual records that have been used to reconstruct NH mean temperature. These consist of individual, or small regional averages of, proxy records collated from those used by Mann and Jones (2003), Esper et al. (2002) and Luckman and Wilson (2005), but exclude shorter series or those with no evidence of sensitivity to local temperature. These records have not been calibrated here, but each has been smoothed with a 20-year filter and scaled to have zero mean and unit standard deviation over the period 1001 to 1980.
Update: This spaghetti graph is changed from the version in the Second Draft. Here’s a replication using data from Osborn and Briffa 2006. The two series with high closing values are Mann’s PC1 (innocuously called “W USA” by Briffa to distract attention from what it is) and Briffa’s version of the Yamal series. The two series which close below the long-term mean are: Fisher’s west Greenland composite (which essentially functions like white noise in a reconstruction) and Taimyr. The 4 series with intermediately high closes are: the Yang composite which uses among other things Dulan junipers and Thompson’s Dunde and Guliya ice core data (or at least one of the many versions of each); Jacoby’s Mongolia series; Tornetrask and Rob Wilson’s Jasper reconstruction. All these series have been discussed at length on previous occasions.
To show the PC1 and Yamal series, I’ve re-plotted this with the Mann PC1 in thick red; Yamal in thin red and other series in light grey. You can see that the rhetorical effect of this diagram depends strongly on these two series. In addition to the discussion of the Mann PC1, Briffa’s substitution of the Yamal series for the Polar Urals update has been discussed before.
The series that have been dropped from the illustration in the Second Draft (which were used in Osborn and Briffa 2006) are plotted below. There are 2 series with high closing: foxtails (which grow about 20 miles from the dominant bristlecone site, Sheep Mountain); the short van Engelen documentary series (which is not a “proxy” in the sense that tree rings are a proxy); one series with a slight positive close ( Tirol) and 3 series with negative closings (Chesapeake; Quebec and Mangazeja).