Post-1980 Proxies #1: Twisted Tree Heartrot Hill

I get a lot of questions about post-1980 proxies and I find it a very interesting question. One would expect that 1998 – the "warmest" year of the millennium – and the 1990s – the "warmest decade" of the millennium would leave a loud signal in a valid proxy. I’m going to start discussing some proxies which I have on hand, starting with a ring width series from the Twisted Tree Heartrot Hill (TTHH) site in northern Canada ending in 1999 and where the proxy shows no strong signal in the 1990s or 1998 as shown below:

Twisted Tree
Figure 1. Site Chronology, Twisted Tree Heartrot Hill. Source, D’Arrigo et al [2004].

TTHH is a classic northern treeline site, used in Jacoby and d’Arrigo’s northern treeline composite, which in turn is used in several of the classic multiproxy studies (Jones et al. [1998], Jones and Mann [2004]) and is used as an individual proxy in MBH98. In MM03, we pointed out that MBH98 used an obsolete version of this series, while an updated version to 1992 was then available. D’Arrigo [2004] updates this site to 1999.

The site chronology obviously does not have a loud 1998 or loud 1990s. The authors propose that the relationship of ring width to temperature is an upside-down U-shaped quadratic. We mention this in MM05 (E&E) but re-iterate it here because the implications of this proposal are profound for multiproxy reconstructions – which hypothesize a linear relationship between ring width and temperature. Obviously, if the relationship is an upside-down U, knowledge of the ring width does not enable you to decide if you are on the warm leg or the cold leg of the reconstruction. D’Arrigo et al [2004] unaccountably fail to make this observation.

D’Arrigo, R. D., R. K. Kaufmann, N. Davi, G. C. Jacoby, C. Laskowski, R. B. Myneni, and P. Cherubini (2004),Thresholds for warming-induced growth decline at elevational tree line in the Yukon Territory, Canada, Global Biogeochem. Cycles,18, GB3021, doi:10.1029/2004GB002249.


  1. John A.
    Posted Feb 16, 2005 at 3:46 AM | Permalink

    If the real relationship is quadratic, and you assume it to be linear, wouldn’t that have the effect of you consisently underestimating warm periods (with attendant droughts)?

  2. Steve Funk
    Posted Feb 16, 2005 at 12:52 PM | Permalink

    The other issue that Mann always brings up is local data vs the sum of world data.

  3. Ed
    Posted Feb 16, 2005 at 3:14 PM | Permalink

    Does anyone have links or info that correlates tree ring patterns to temperature? I always thought the rings were wider in wetter years, and thinner in drier ones. And I’d love to see some info on how this ties into global warming.


  4. Murray Duffin
    Posted Sep 7, 2005 at 10:23 AM | Permalink

    It is interesting that the Maunder and Dalton minima are clearly visible, as well as the post 1930s cooling. More evidence that Maunder and Dalton were not just northern Europe phenomena. Murray

  5. Steve McIntyre
    Posted Sep 7, 2005 at 11:01 AM | Permalink

    Murray, I’m glad you brought this post back on the screen. I get the impression that quite a few of the “missing” tree ring proxy studies of the 1990s look like this. That’s why we hear about glacier recession and not tree rings now. The archived Jacoby sites are all south-facing.

  6. TCO
    Posted Sep 10, 2005 at 7:58 PM | Permalink

    The key issue which we seem to keep coming back to, is how to calibrate ring width as a proxy at all. This should be based on current observations…not backed out from gridcell comparisons or the like. I mean real botanical laboratory style observations. These are important calibrative type studies. I would think that any single series that goes back in time or any temp reconstruction would refer to such calibrative studies.

  7. Hans Erren
    Posted Jan 13, 2006 at 1:49 AM | Permalink

    re 6:
    like this one

  8. Steve Sadlov
    Posted Feb 17, 2006 at 4:22 PM | Permalink

    If I recall correctly, 1997 and 98 were El Nino years, with 97 being a stronger El Nino. I also seem to recall that by December of 98, we were flipping into a La Nina, based on the fact that it snowed at my house (~1000′ elevation, very close to the ocean). I certainly witnessed lots of growth in my location – 100 % due to moisture. I would also reckon that meanwhile, up in Alaska, there would have been a moisture deficit especially away from the coast, until early ’99. Are trees more of an ENSO proxy than a temperature proxy?

3 Trackbacks

  1. […] White Spruce at Northern Treeline The decline of ring widths with increasing temperatures was reported in D’Arrigo et al [2004], about which I reported briefly here: […]

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