Uncertainty in climate-sensitivity estimates
Based on reconstructions of past temperatures from proxy data, Hegerl et al. estimate a confidence interval for climate sensitivity that suggests a substantially reduced probability of very high climate sensitivity compared with previous empirical estimates. Here I show that the inference procedure used by Hegerl et al. neglects uncertainties in temperature reconstructions and in the estimated climate sensitivity and can even be used to infer that the climate sensitivity is zero with vanishing uncertainty. Similar procedures based on temperature reconstructions from proxy data generally underestimate uncertainties in climate sensitivity.
© 2007 Nature Publishing Group. Received 19 May 2006; accepted 13 December 2006. Published online 28 February 2007. Competing financial interests: declared none.