Past changes in the Earth's surface energy balance propagate into the subsurface and appear as perturbations of the subsurface thermal regime. A singular value decomposition inversion (SVD) scheme has been used to reconstruct surface heat flux histories (SHFH) from the heat flux anomalies detected in the subsurface. Synthetic data tests yield results in agreement with analytical expressions. Inversion of a temperature log from central Canada is used to illustrate this procedure. Results show that reconstruction of SHFH is possible with existing data. Application of this method to the existing geothermal data base should permit a quantification of the energy balance at the Earth's surface for the past few centuries. ¿ 2001 American Geophysical Union