2006/06/30 by Stefan Rahmstorf · 1 citation
Earth and Planetary Sciences · Environmental Science · #Tree-ring climate responses #Plant Water Relations and Carbon Dynamics #Climate variability and models #Climate change #Environmental science #Climatology #Earth science #Geology #Oceanography
paper · doi:10.1126/science.312.5782.1872b
openalex publication_date 2006/06/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/23
This Report was also discussed in the U.S. Senate in 2005 (3).In this discussion, it has been overlooked that von Storch et al.'s Supporting Online Material (SOM) in fact supports the Mann et al. reconstruction.von Storch et al. presented tests of the climate proxy method with two climate models: the HadCM3 model (shown only in the SOM) and the ECHO-G model.Both are compared in the figure.The HadCM3 simulation (solid blue) is consistent with the climate proxy data reconstruction (grey band).The ECHO-G model has since been found to be afflicted by a major artificial climate drift due to an undocumented, inappropriate initialization procedure (4).The error of simulated proxies (dotted blue) found in the HadCM3 model is smaller than the error margin given by Mann et al. for their method and shown in the IPCC report (5).For the time period common to both models, the RMS error of the simulated proxies is 0.24C in ECHO-G, but only 0.07C in HadCM3-less than one-third.The two models thus give rather different, conflicting results about the potential errors of proxy reconstructions.This is not mentioned in the Report, which merely states, "Similar results are obtained with a simulation with the third Hadley Centre coupled model (HadCM3), demonstrating that the results obtained here are not dependent on the particular climate characteristics of the ECHO-G simulation" (p.680).In addition, it has since been found (6) that the proxy method was implemented incorrectly by von Storch et al.; with correct implementation, the error is even smaller in HadCM3 than the 0.07C shown here.A similar, more recent test with the NCAR climate system model ( 7) also suggests only small errors for the proxy method, supporting the climate reconstruction of the past millennium by Mann et al.