Possible causes of the underestimation of paleoclimate low-frequency variability by statistical methods
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The Northern Hemisphere mean surface temperature has shown a significant positive trend over the past two centuries. On the basis of the well-known reconstructions of global climate from proxy data, the conclusion is made that the current warming has been unprecedented during at least the past two millennia. On the other hand, it was demonstrated in  that the existing statistical models strongly underestimate the low-frequency variability of global annual mean temperature, thus making the conclusion drawn above questionable. At present, the results of  are interpreted as evidence that the Mann reconstruction is invalid . To our knowledge, however, it is too early to draw such conclusions. What is the cause of smoothing low-frequency variability? To what extent are various statistical models used for paleoclimate reconstruction that is subject to this effect? To answer these questions, numerical experiments are performed with data sets of annual mean surface temperature over the past millennium that are simulated with the ECHO-G coupled ocean-atmosphere general circulation model.
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- 7.E. Zorita, F. Gonzalez-Rouco, and S. Legutke, “Testing the Mann et al. (1998) Approach to Paleoclimate Reconstructions in the Context of a 1000-yr Control Simulation with the ECHO-G Coupled Climate Model,” J. Clim. 16, 1378–1390 (2003).Google Scholar
- 8.P. D. Jones and M. E. Mann, “Climate over Past Millennia,” Rev. Geophys. 42, doi:10.1029/2003RG000143 (2004).Google Scholar
- 9.A. I. Chavro and V. P. Dymnikov, Methods of Mathematical Statistics in Atmospheric Physics (IVM RAN, Moscow, 2000) [in Russian].Google Scholar
- 10.A. M. Oboukhov, “On Statistical Orthogonal Expansions of Empirical Functions,” Izv. Akad. Nauk SSSR, Ser. Geofiz., No. 3, 432–439 (1960).Google Scholar
- 11.E. V. Dmitriev, “Analysis of Methods for Processing Proxi Measurements of Geophysical Quantities and Estimating Errors in Their Interpretation,” Inform.-Izmerit. Upravl. Sist. 2(5), 12–22 (2004).Google Scholar
- 12.Yu. P. Pyt’ev and A. I. Chulichkov, “Recurrent Techniques of Measurement Reduction,” Mat. Model. 1(8), 22–44 (1989).Google Scholar
- 13.A. I. Chavro and E. V. Dmitriev, “Statistical Model for Reconstruction of the Regional Structure of Geophysical Fields,” Meteorol. Gidrol., No. 6, 39–49 (2002).Google Scholar
- 15.S. G. Dobrovol’skii, Climatic Changes in the Hydrosphere-Atmosphere System (Geos, Moscow, 2002) [in Russian].Google Scholar