A comparison of five different analyses in the interpretation of five borehole temperature data sets

To assess the effectiveness of various methods in inferring ground surface temperature history (GSTH) from perturbed borehole temperature data, five synthetic and real data sets were prepared and disseminated to interested groups for analysis. This report summarizes the results obtained by five different groups using different inverse methods. The five inverse methods yield similar results inasmuch as the salient features of the GSTH are concerned. However, the estimated GSTHs differ in details of the timing and the magnitude of changes. This is attributed to the differences in parameterization schemes and to the different a priori constraints imposed on the GSTH. Better agreement among the inverse methods may be obtainable when information other than that contained in the borehole data is incorporated.