Supplemental Information for PNAS Article "Proxy-Based Reconstructions of Hemispheric and Global Surface Temperature Variations over the Past Two Millennia"

Readme file describing files and directories found on this site

Supplementary Figures and Information (PDF)
UPDATE 1 December 2008: Supplementary Figure S8a had a small error due to improper calculation of the validation statistics.
UPDATE 4 November 2009: Another error was found in the corrected Supplementary figure S8a from December 2008: The previously posted version of the figure had an error due to incorrect application of the procedure described in the paper for updating the network in each century increment. In the newly corrected figure, we have added the result for NH CPS without both tree-rings *and* the 7 potential "problem series." Each of the various alternative versions where these sub-networks of proxy data have been excluded fall almost entirely within the uncertainties of the full reconstruction for at least the past 1100 years, while larger discrepancies are observed further back for the reconstruction without either tree-ring data or the 7 series in question, owing to the extreme sparseness of the resulting sub-network.
The new figure can be downloaded here (PDF)

1209proxynames.xls *** Updated 25 September 2008 to correct latitude/longitude values***
*** Updated 16 July 2009: This Excel spreadsheet was updated to include metadata that were incorrect or erroneously excluded from the previous version of this file. Only proxy metadata were updated; no data used in the calculations were affected. ***
NOTE (23 Aug 2010): The color shading in this document can be ignored. Proxy data type can be determined by using the "data type code" (Column D).

Validation statistics:
skillsig.xls: Skill significance levels from Monte Carlo simulations

Code: This page contains the Matlab scripts for both the CPS and EIV techniques.

Data: This page contains data needed for calculations.

UPDATE 3 October 2008: An error was found in the location information for one of the proxies included in the study. For more information, including the impact of this error on the results, please see the A_README.txt file on this page.

UPDATE 3 February 2009: An off-by-one error was found in the degrees of freedom used for screening proxy data. This has the effect of slightly reducing the effective P values from P=0.10 to P=0.11-0.12 for decadal screening. For more information, please see the README.txt file in this directory.

UPDATE 24 June 2011: People have asked whether the use of the Tiljander proxies in the EIV surface temperature reconstructions matters for the conclusions of the study. The answer, as provided previously in the literature (see this reply to a comment in PNAS) is no.

The impact of whether or not these proxies are used was demonstrated to be minimal for the Northern Hemisphere land+ocean EIV reconstruction featured in this study [see Figure S7b of the Supplementary Information, which compares the reconstruction both with and without 7 potential 'problem proxies', that include the Tiljander proxies; a similar comparison was also made in Figure S8 of the Supplementary Information for the followup article by Mann et al (2009)] . The same holds for the specific global mean EIV temperature reconstruction used in our more recent study of temperature/sea level relationships over the past 2000 years [Kemp et al (2011)] as shown in the plot below (interestingly, eliminating the proxies in question actually makes the reconstruction overall slightly cooler prior to AD 1000, which -- as noted in the article -- would actually bring the semi-empirical sea level estimate into closer agreement with the sea level reconstruction prior to AD 1000).

land+ocean global full EIV reconstruction
Figure Caption: Comparison of Mann et al (2008) global mean (land+ocean) temperature reconstruction with and without the 7 proxy records discussed in the text [shown in both cases is the low-frequency (>20 year timescale) component of the reconstruction]. Reconstruction is based on calibration against the HadCRUT3 series using the global proxy network

Data series used in the above plot (1st column is Year, 2nd column is Reconstruction:
glglhadfulsm20: The blue line; the original reconstruction
glglhadno7sm20: The red line; the reconstruction without the 7 proxy records