Comment on cp-2021-189

Abstract

Currently available data assimilation-based reconstructions of past climate variations have only used statistical proxy system models to make the link between the climate model outputs and the indirect observations from tree rings. However, the linearity and stationarity assumptions of the statistical approach may have limitations. In this study, we incorporate the process-based dendroclimatic model MAIDEN into a data assimilation procedure, using as a test case the reconstruction of near-surface air temperature, precipitation and winds in the mid-latitudes of the Southern Hemisphere over the past 400 years. We compare our results with a data assimilation approach including a linear regression as a proxy system model for tree-ring width proxies. Overall, when compared to instrumental data, the reconstructions using MAIDEN as a proxy system model offer a skill equivalent to the experiment using the regression model. However, knowing the advantages that a process-based model can bring and the improvements that can still be made with MAIDEN, those results are promising.