A Strange Truncation of the Briffa MXD Series

Post-1960 values of the Briffa MXD series are deleted from the IPCC TAR multiproxy spaghetti graph. These values trend downward in the original citation (Briffa [2000], see Figure 5), where post-1960 values are shown. The effect of deleting the post-1960 values of the Briffa MXD series is to make the reconstructions more "similar". The truncation is not documented in IPCC TAR. In most cases, people would ask: who at IPCC truncated this series? why did they do so? who approved the truncation? what process was involved in approving the truncation? I’ve gone through a laborious process to calculate what the untruncated IPCC spaghetti graph would look like and show the calculations here.

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11 Comments

  1. Dave Dardinger
    Posted May 1, 2005 at 8:56 PM | Permalink

    I note that on my NetScape browser at least, the drawings for figures 1-3 don’t appear. I don’t know if others are having this problem or not.

    Steve: I’ve fixed 2 of the figures. I’m still having trouble with the other one.

  2. Steve McIntyre
    Posted May 2, 2005 at 7:21 AM | Permalink

    I’ve edited the introduction of this post this morning and fixed the other figure. Steve

  3. John A
    Posted May 2, 2005 at 7:35 AM | Permalink

    Figure 7 is still not working.

    Steve: It works when I try.

  4. Paul Gosling
    Posted May 3, 2005 at 3:11 AM | Permalink

    The reason for the decline in tree ring density in the late 20th century could be increased nitrogen deposition. This can certainly reduced wood density.

  5. Ferdinand Engelbeen
    Posted May 4, 2005 at 5:01 PM | Permalink

    Paul,

    If nitrogen is to blame, ring density will be lower, but ring width would increase. Is there any indication for that? I remember that tree rings in Belgium have a growth spurt in the last halve century, probably by more CO2, but maybe also by more nitrogen in a densily populated and industrialised country. May be solved by a density/ring width comparison…

  6. Paul Gosling
    Posted May 5, 2005 at 8:17 AM | Permalink

    This is not something I know too much about, and there does tend to be some site to site variation, but generally speaking adding nitrogen increases ring width and reduces wood density.

  7. TCO
    Posted Sep 18, 2005 at 7:33 PM | Permalink

    It’s a good point, but you need to show the bottom line more quickly. It’s pretty tedious to wade through all this stuff to get the result. Why not just have a “with and without” picture right at the beginning?

  8. Steve McIntyre
    Posted Sep 18, 2005 at 8:25 PM | Permalink

    Good point. I agree. When I’m editing other people’s stuff, I often make the same point.

  9. TCO
    Posted Sep 18, 2005 at 8:27 PM | Permalink

    It always looks easier from the dummies or the kibbitzer’s position…

  10. Steve McIntyre
    Posted Sep 18, 2005 at 8:35 PM | Permalink

    Roger Pielke noted up this post approvingly at sciencepolicy/prometheus last spring.

    You’d never be able to do something like this in a prospectus.

    As someone who’s dealt a lot with promoters, I always feel like these guys are promoting.

  11. TCO
    Posted Sep 23, 2005 at 10:37 PM | Permalink

    Yeah. I agree. Some promotion (of self or of overpuffing the importance of work) is common in 30something ambitious academic turks. But this stuff is just a tendentious mess. And listening to all the rationales and the lack of intellectual vibrancy and curiousity…shows me a field of arguers, not discoverers.

21 Trackbacks

  1. By The Trick « Climate Audit – mirror site on Nov 26, 2009 at 7:25 PM

    [...] discussion of these issues is at Climate Audit here here here and more recently by Jean S [...]

  2. [...] my knowledge, no one noticed or reported this truncation until my Climate Audit post in 2005 here. The deletion of the decline was repeated in the 2007 Assessment Report First Order and Second [...]

  3. [...] discussion of these issues is at Climate Audit here here here and more recently by Jean S here. Jean S and UC report at CA that the puzzling end point [...]

  4. [...] To my knowledge, no one noticed or reported this truncation until my Climate Audit post in 2005 here. The deletion of the decline was repeated in the 2007 Assessment Report First Order and Second [...]

  5. By A Change In Climate, Part 1 « ORBIS on Dec 13, 2009 at 3:37 AM

    [...] This “apparent” truncation of data had been spotted and discussed at Climate Audit as far back as 2005: Post-1960 values of the Briffa MXD series are deleted from the IPCC TAR multiproxy spaghetti graph. These values trend downward in the original citation (Briffa [2000], see Figure 5), where post-1960 values are shown. The effect of deleting the post-1960 values of the Briffa MXD series is to make the reconstructions more “similar”. The truncation is not documented in IPCC TAR. In most cases, people would ask: who at IPCC truncated this series? why did they do so? who approved the truncation? what process was involved in approving the truncation? (Climate Audit, A Strange Truncation of the Briffa MXD Series) [...]

  6. [...] green line “gets lost” around 1960 and never reappears. McIntyre noticed this in 2005, and raised the issue in a comment on a later IPCC report. His comment was rejected. Page 1 of 2 [...]

  7. [...] was truncated in 1960, rather than showing the post-1960 decline. I posted on this in May here and here showing how the IPCC truncation was imperceptible without a [...]

  8. By A “Fair Sample”? « Climate Audit on Apr 15, 2010 at 7:33 PM

    [...] relatively favorably in my May 2005 post in which I first drew attention to the “trick” A Strange Truncation of the Briffa MXD Series (see image below). I had no complaint with the original Briffa articles – it was the IPCC [...]

  9. [...] The truncation of the Briffa reconstruction in IPCC TAR was first reported at CA in May 2005 here; the construction of the smooth in the IPCC diagram was dissected by Jean S and UC and reported at [...]

  10. [...] 20th century downturn in the Briffa 2001 graphic in the IPCC graphic, that I observed some time ago here. Since data truncation is in the news, I was going to update the graphic in this post to better show [...]

  11. [...] hide the decline. The deletion of adverse data to hide the decline was first reported at CA in 2005 here in connection with IPCC TAR spaghetti [...]

  12. [...] hide the decline. The deletion of adverse data to hide the decline was first reported at CA in 2005 here in connection with IPCC TAR spaghetti [...]

  13. By Briffa on Yamal Impact « Climate Audit on Mar 31, 2011 at 12:47 PM

    [...] is not the only instance of Briffa truncating data. As reported previously at CA, Briffa truncated the “divergent” portion of Briffa 2001 in IPCC TAR and, despite [...]

  14. By Jaeah’s Investigation « Climate Audit on Apr 22, 2011 at 10:49 AM

    [...] years ago, I wondered the same thing – see CA post here, leading me to do a blowup of the graphic, only then discovering that there had been an unreported [...]

  15. [...] and this finding shows an inverse relation with temperature to tree height. Maybe this is why Briffa had to truncate uncooperative tree ring data post 1960 and Mike’s Nature trick was used to “hide the [...]

  16. [...] and this finding shows an inverse relation with temperature to tree height. Maybe this is why Briffa had to truncate uncooperative tree ring data post 1960 and Mike’s Nature trick was used to “hide the [...]

  17. [...] and this finding shows an inverse relation with temperature to tree height. Maybe this is why Briffa had to truncate uncooperative tree ring data post 1960 and Mike’s Nature trick was used to “hide the [...]

  18. [...] A Strange Truncation of the Briffa MXD Series [...]

  19. [...] A Strange Truncation of the Briffa MXD Series [...]

  20. [...] A Strange Truncation of the Briffa MXD Series [...]

  21. [...] deleted. Now this was hard to see because of the coloring in the spaghetti graph. I discussed this previously here showing the following blowup of the IPCC [...]

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