Response “[to Comment on ‘On past temperatures and anomalous late‐20th‐century warmth’”]

Soon and his colleagues (‘S03’) fail to address any of the three specific issues we raised in our Eos criticism (‘M03’) of their previous work (‘SB03’). These were the need for critical evaluation of proxy data to be used; consistent assimilation of widespread, well‐dated, and resolved records; and the objective, quantitative calibration of these records [see also Bradley et al., 2003]. S03, instead, start with the implausible claim that we agree with their assertion, “knowledge of past climatic changes does not have a direct bearing on the climatic effects of anthropogenic carbon dioxide.…” Reconstructions of past temperature histories do, indeed, have such a bearing. They provide one of several independent lines of evidence supporting the consensus scientific conclusion, expressed in the 2001 report of the Intergovernmental Panel on Climate Change (IPCC), that anomalous, hemispheric, late‐20th‐century warmth cannot be explained by natural factors. S03 follow with an equally puzzling assertion that “M03 relies mainly on a northern hemisphere reconstruction of average annual temperature by Mann et al. [1999].” Our article, quite to the contrary demonstrated that nearly a dozen different published estimates based on proxy data and model simulations give the same picture—anomalous, late‐20th‐century warmth that is unprecedented in a millennial or longer context.