Climatic Change

, Volume 104, Issue 3, pp 423–436

On the generation and interpretation of probabilistic estimates of climate sensitivity


DOI: 10.1007/s10584-009-9715-y

Cite this article as:
Annan, J.D. & Hargreaves, J.C. Climatic Change (2011) 104: 423. doi:10.1007/s10584-009-9715-y


The equilibrium climate response to anthropogenic forcing has long been one of the dominant, and therefore most intensively studied, uncertainties in predicting future climate change. As a result, many probabilistic estimates of the climate sensitivity (S) have been presented. In recent years, most of them have assigned significant probability to extremely high sensitivity, such as P(S > 6C) > 5%. In this paper, we investigate some of the assumptions underlying these estimates. We show that the popular choice of a uniform prior has unacceptable properties and cannot be reasonably considered to generate meaningful and usable results. When instead reasonable assumptions are made, much greater confidence in a moderate value for S is easily justified, with an upper 95% probability limit for S easily shown to lie close to 4°C, and certainly well below 6°C. These results also impact strongly on projected economic losses due to climate change.

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Research Institute for Global ChangeJapan Agency for Marine-Earth Science and TechnologyYokohamaJapan

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