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Equilibrium climate sensitivity in light of observations over the warming hiatus


A Corrigendum to this article was published on 24 June 2015

This article has been updated


A key uncertainty in projecting future climate change is the magnitude of equilibrium climate sensitivity (ECS), that is, the eventual increase in global annual average surface temperature in response to a doubling of atmospheric CO2 concentration. The lower bound of the likely range for ECS given in the IPCC Fifth Assessment Report (AR5; refs 1, 2) was revised downwards to 1.5 °C, from 2 °C in its previous report3, mainly as an effect of considering observations over the warming hiatus—the period of slowdown of global average temperature increase since the early 2000s. Here we analyse how estimates of ECS change as observations accumulate over time and estimate the contribution of potential causes to the hiatus. We find that including observations over the hiatus reduces the most likely value for ECS from 2.8 °C to 2.5 °C, but that the lower bound of the 90% range remains stable around 2 °C. We also find that the hiatus is primarily attributable to El Niño/Southern Oscillation-related variability and reduced solar forcing.

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Figure 1: Comparison between observations on SAT anomaly and corresponding model output using the posterior PDF generated by using observations up to 2011.
Figure 2: The posterior marginal PDF of ECS estimated from historical observations over successively longer time periods.
Figure 3: Characteristics of PDFs of ECS and EVD as observations accumulates.

Change history

  • 14 April 2015

    In the version of this Letter originally published, in the third paragraph, the section of text including ‘Our analysis differs... at depths below 700m (refs 5,8,13).’ was unclear and should have been: 'Our analysis differs from previous methodologically related statistical estimates of ECS in that we distinguish observations of global mean near-land surface temperature (GMLST) from those of global mean sea surface temperature (GMSST) and use ocean heat content (OHC) observations continuous over time to a greater depth (2,000m instead of 700 m), a potentially important addition as heat accumulation during the hiatus is thought to be particularly strong at depths below 700m (refs 5,8,13).' Further, in the Methods section, radiative forcing should have been described as effective radiative forcing. These errors have been corrected in all versions of the Letter.

  • 10 June 2015

    In the version of this Letter originally published, ref. 9 was incorrectly cited twice; the sentence including the second occurrence should have read: "In contrast to other studies4, we find that the recovery from Mt Pinatubo is stronger than the cooling caused by the small volcanoes that has occurred since the early 2000s." This error has been corrected in the online versions of the Letter.


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D.J.A.J. wants to thank the Swedish Energy Agency and Carl Bennet AB for financial support. C.T. was supported by the Regional and Global Climate Modeling Program (RGCM) of the US Department of Energy’s Office of Science (BER), Cooperative Agreement DE-FC02-97ER62402. O.H. was supported by the Knut and Alice Wallenberg Foundation and the Swedish Research Council. C. Azar is acknowledged for useful comments.

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D.J.A.J. designed and performed the research with input from the other authors. All authors contributed to writing the paper.

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Correspondence to Daniel J. A. Johansson.

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Johansson, D., O’Neill, B., Tebaldi, C. et al. Equilibrium climate sensitivity in light of observations over the warming hiatus. Nature Clim Change 5, 449–453 (2015).

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