Climate Variability in the Americas from Treeline Environments

In 1999, the IAI launched a major initiative entitled Assessment of Present, Past and Future Climate Variability in the Americas from Treeline Environments . They state: “The overarching scientific goal of this project was to reconstruct climate variability over a major global transect from Alaska to Tierra del Fuego.” While Mann has told us that he had to use chronologies ending by about 1980 because it was too expensive and time consuming for dendrochronologists to collect new data, the report on this initiative stated:

The project has produced considerable data in the form of new tree-ring chronologies, climate reconstructions and related materials. Extensive collections have taken place at over 400 sites, resulting in over 200 chronologies from more than 20 different species.

In Canada alone, they report the collection of 145 new chronologies:

In total, since the inception of the Yukon work in 1999 we have collected approximately 145 new chronologies (Table 2) including over 110 spruce sites (mainly P. glauca).

They include the following attractive diagram showing the range and scope of this collection:
iaicr9.jpg

It sounds like this should be just what the doctor ordered in terms of providing temperature-limited chronologies which can be used to verify the hypothesis of a linear relationship between ring widths and temperature at treeline sites. Even better, it turns out that the collectors were explicitly mandated to create a public archive of their results as follows:

4. To produce a database of tree-ring chronologies and environmental reconstructions that will be freely and permanently accessible to the scientific community for climatic analyses and human impact assessments. This will include a central website for our proposed project, and contributions to the International Tree-Ring Databank (ITRDB) and the paleoclimatic database maintained by the U.S. National Geophysical Data Center in Boulder, Colorado (USA).

They published lengthy annual reports on their operations url with the final report here by Brian Luckman entitled: Assessment of Present, Past and Future Climate Variability in the Americas from Treeline Environments: IAI CRN03 FINAL REPORT 2005. The final report is very self-congratulatory on how the objectives were fulfilled, with accomplishments estimated at 150% and even 300% of objectives. However, despite the self-congratulation and despite the explicit policy from the funders, it appear to me that measurement data for less than 10% of the sites of the 400 sites (and probably less than 5%) have been archived.

I cross-checked ITRDB for the archiving of this seemingly ideal collection of chronologies, as any program archives would reach into the 2000s or at a minimum into the late 1990s. However, when I checked, I found no chronologies with measurements more recent than 1995 from either Chile or Argentina; I found no archives whatever from Bolivia, Ecuador or Peru. I located only 7 sites from Mexico (although many more sites were referenced in the Annual Report), but the text in the 2005 Annual Report described them as precipitation proxies. Hughes discusses the development of new bristlecone chronologies but nothing’s been archived. Biondi has archived one site from Mexico. Connie Woodhouse has archived many precipitation sites; I wrote to Connie Woodhouse and inquired about temperature-sensitive sites and she identified criteria from which I identified 5 archived sites (which I will post on.) I found only one qualifying site from the Yukon (archived by Jacoby who was not funded by IAI) and only a few recent archived sites from B.C., which do not appear to be associated with this program. 8 of 9 archived sites in Alberta with values more recent than 1995 were from Meko’s supposedly precipitation proxies. A number of Luckman chronologies were the source for Rob Wilson publications, but none of these measurement data sets have been archived (other than the chronology without measurement data for Athabaska/Icefields). I wrote to Luckman who said that “as I knew”, the Athabaska data was archived, although they have not archived any measurement data and this is only one site. The report says of the Canadian data:

Several PIs have deposited their chronologies and some reconstructions with the International Tree-Ring Data Bank housed at the NOAA Paleoclimate Facility in Boulder, Colorado. This is the appropriate archive for this material and is used by a global network of international scientists (see (http://www.ncdc.noaa.gov/paleo/pdsi.html). Other PIs have or are developing their own databases (those of the two Canadian CoPIs consist of over 200 each collected in the last 10-15 years) that will also be submitted to ITRDB once chronology development and/or climate reconstructions have been completed.

However, this has obviously not taken place yet. So it appears that the administrators and funders of this program have made no effort whatever to ensure compliance with the explicit IAI objective of creating archives in pblic databases.

If you browse through the 2005 Annual Report, which I’m not going to summarize further, you will find many references to precipitation as a limiting factor, even in the southern Canadian Cordillera. So just because a site is a treeline site doesn’t appear to mean that it’s a “temperature proxy”. It seems that only some treeline sites are now viewed as temperature proxies. One statement (in the Argentina section) says:

It is generally assumed, based mainly on studies from extra-tropical mountains, that tree growth at upper treelines is primarily controlled by summer temperatures. In the subtropical mountains of Northwestern Argentina (c. 23°S), annual precipitation decreases with elevation from more than 1500 mm at 1200-1500 m, to less than 200 mm above 4000 m. Studies based on Juglans australis (ca. 1800 m); Alnus acuminata (ca. 2700m) Prosopis ferox (at 3500 m) and Polylepis tarapacana (ca. 4750m) show that radial growth of the four species is largely controlled by precipitation (Morales et al., 2004). Therefore the generalized idea of upper-treeline growth limited by summer temperatures should be carefully evaluated in low-latitude environments and does not apply to subtropical areas with severe water deficits or strong moisture seasonality.

This statement is explicitly limited to subtropical sites. However, similar statements are made about Mexico. To date, every U.S. treeline site discussed by Woodhouse in a publication has been for a drought/precipitation reconstruction; chronologies as far north as British Columbia were used for precipitation reconstructions:

Ongoing work from collections in the Canadian Rockies and southern BC has also developed the first regional precipitation reconstructions, drought histories and some initial streamflow reconstructions (Watson and Luckman 2004, 2005, in press).

The review also notes that:

Luckman and Wilson (2005) have also developed a millennial length (950-1994) maximum summer temperature reconstruction from the Columbia Icefield area in the Canadian Rockies that appears to reflect broad Northern Hemisphere trends.

Although the reconstruction and chronology are archived, the underlying measurement data is not archived, nor is the data for other treeline sites reported in Wilson and Luckman 2003, a reconstruction of maximum summer temperature from upper treeline sites.

The environment of the White Mountains bristlecones and the Dulan junipers is obviously moisture stressed. Their latitude 37-38N is bracketed to the north and south by precipitation rather than temperature reconstructions; in the Dulan case, any relationship with temperature is actually thought to be negative. So if a treeline site is not necessarily a temperature proxy, how does one actually provide an objective ex ante criterion for a site to be a “temperature” proxy. The search continues.


5 Comments

  1. jae
    Posted Mar 31, 2007 at 7:27 PM | Permalink

    To date, every U.S. treeline site discussed by Woodhouse in a publication has been for a drought/precipitation reconstruction; chronologies as far north as British Columbia were used for precipitation reconstructions:

    Yup, that is what tree ring studies are good for.

  2. Steve Sadlov
    Posted Apr 2, 2007 at 9:57 AM | Permalink

    Fresh from a self funded quick, qualitative field observation at the Western boundary of the Great Basin. More to come on this. Suffice it to say, I will be addressing the issue of moisture limitations at tree line in alpine terrains which are biotic islands in arid and semi arid zones.

  3. Steve McIntyre
    Posted Apr 2, 2007 at 10:15 AM | Permalink

    #2. Look forward to your report and will be happy to post up pictures with your discussion.

  4. Steve McIntyre
    Posted Apr 2, 2007 at 11:52 AM | Permalink

    Rob Wilson has objected on another thread to this report stating:

    The southern Canadian Cordillera (i.e. southern British Columbia) has TWO tree-lines:

    Lower tree-line – moisture stressed tree-line – tree-species are Ponderosa pine and Douglas fir.

    Upper tree-line – temperature controlled environment – Engelmann spruce, larch, whitebark pine etc.

    so – completely different environments and completely different species.

    I don’t see that anything in the above post states otherwise. Upper and lower treelines have been discussed at this site previously in connection with bristlecones. For greater clarity, I’ve added a couple of sentences to the above post referring to Rob Wilson’s temperature reconstructions as follows. (I’ve discussed data archiving as data archiving was one of the stated objectives of the program and I’d spent much of the post reporting on that issue.

    The review also notes that:

    “Luckman and Wilson (2005) have also developed a millennial length (950-1994) maximum summer temperature reconstruction from the Columbia Icefield area in the Canadian Rockies that appears to reflect broad Northern Hemisphere trends.”

    Although the reconstruction and chronology are archived, the underlying measurement data is not archived, nor is the data for other treeline sites reported in Wilson and Luckman 2003, a reconstruction of maximum summer temperature from upper treeline sites.

    I didn’t mean to neglect Rob Wilson’s work on temperature reconstructions in this summary. My attention was really directed towards work less familiar to me and noting the very low return of archived results from this program. I will endeavor to re-read Rob’s work.

    Rob, one of the underlying problems here is that IPCC 4AR failed to do an assessment of recent dendro work, by and large limiting itself to reporting on the multiproxy reconstructions. I’ve spent quite a bit of time recently trying to see what up-to-data proxy information actually looks like and welcome any suggestions on series or studies that you think I should look at it.

  5. twq
    Posted May 12, 2007 at 5:14 AM | Permalink

    Re: The environment of the White Mountains bristlecones and the Dulan junipers is obviously moisture stressed. Their latitude 37-38N is bracketed to the north and south by precipitation rather than temperature reconstructions; in the Dulan case, any relationship with temperature is actually thought to be negative. So if a treeline site is not necessarily a temperature proxy, how does one actually provide an objective ex ante criterion for a site to be a “temperature” proxy.

    It is very funny. You have not been to this place for on-site monitoring. Why are you still so adamant about it? It is funny, funny and funny! Science is based on evidence, not your allegation. It does not mean it just because you are so insistent on it. If you want to confirm something, I suggest you should go for fieldwork and make a experiment monitoring, and only in this case, I can believe what you said. Otherwise, I am afraid that some misinformation produce.

One Trackback

  1. [...] I’ve been re-visiting some proxy data; I noted last summer that Rob Wilson had archived a considerable amount of B.C. data in Aug 2007 and noticed that he subsequently archived the data versions as used in Wilson et al 2007 at NCDC here in Sept 2007. (Not all of Rob’s data is archived as he isn’t in control of all the data that he’s been involved with; for example, Brian Luckman of the University of Western Ontario is holding out on archiving data, notwithstanding commitments of the IAI program discussed here. [...]

Follow

Get every new post delivered to your Inbox.

Join 3,262 other followers

%d bloggers like this: