Northern Hemisphere Temperature Variability for the Past Three Centuries: Tree-Ring and Model Estimates

We compare Northern Hemisphere energy-balance-model temperature calculations to an annual temperature reconstruction based on 20 tree-ring width records from latitudinal and elevational treeline sites in northern North America, Scandinavia, Siberia and Mongolia for the past three centuries. The energy-balance model uses three primary forcings; solar, volcanic, and anthropogenic trace gas and aerosol variations. Several different parameterizations of the forcings are compared. The best agreement (r = 0.8) is found when the annual reconstruction is compared to a version of the model using (1) the Dust Veil Index of Lamb, (2) a solar parameterization which includes the length of the solar cycle, and (3) anthropogenic forcing. The implication is that all three forcings are important in explaining the temperature variations. The general similarity in low-frequency trends between the two independently-derived time series supports the validity of both the model estimates and the tree-ring reconstruction.