Nature 442, 627 (10 August 2006) | doi:10.1038/442627b; Published online 9 August 2006

Authors were clear about hockey-stick uncertainties

Raymond S. Bradley1, Malcolm K. Hughes2 & Michael E. Mann3

  1. Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
  2. Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona 85721, USA
  3. Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania 16802, USA


Your News story "Academy affirms hockey-stick graph" (Nature 441, 1032; 2006) states that the US National Academy of Sciences (NAS) panel "concluded that systematic uncertainties in climate records from before 1600 were not communicated as clearly as they could have been". This conclusion is not stated in the NAS report itself, but formed part of the remarks made by Gerald North, the NAS committee chair, at the press conference announcing the report.

The name of our paper is "Northern Hemisphere temperatures during the past millennium: inferences, uncertainties, and limitations" (Geophys. Res. Lett. 26, 759–762; 1999). In the abstract, we state: "We focus not just on the reconstructions, but on the uncertainties therein, and important caveats" and note that "expanded uncertainties prevent decisive conclusions for the period prior to AD 1400". We conclude by stating: "more widespread high-resolution data are needed before more confident conclusions can be reached." It is hard to imagine how much more explicit we could have been about the uncertainties in the reconstruction; indeed, that was the point of the article!

The subsequent confusion about uncertainties was the result of poor communication by others, who used our temperature reconstruction without the reservations that we had stated clearly.