Publication Abstracts

Sherwood et al. 2020, in press

Sherwood, S., M.J. Webb, J.D. Annan, K.C. Armour, P.M. Forster, J. Hargreaves, G. Hegerl, S.A. Klein, K.D. Marvel, E.J. Rohling, M. Watanabe, T. Andrews, P. Braconnot, C. Bretherton, G.L. Foster, Z. Hausfather, A.S. von der Heydt, R. Knutti, T. Mauritsen, J.R. Norris, C. Proistosescu, M. Rugenstein, G.A. Schmidt, K.B. Tokarska, and M.D. Zelinka, 2020: An assessment of Earth's climate sensitivity using multiple lines of evidence. Rev. Geophys., in press, doi:10.1029/2019RG000678.

We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation, and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although higher-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent, and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

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BibTeX Citation

@unpublished{sh02800e,
  author={Sherwood, S. and Webb, M. J. and Annan, J. D. and Armour, K. C. and Forster, P. M. and Hargreaves, J. and Hegerl, G. and Klein, S. A. and Marvel, K. D. and Rohling, E. J. and Watanabe, M. and Andrews, T. and Braconnot, P. and Bretherton, C. and Foster, G. L. and Hausfather, Z. and von der Heydt, A. S. and Knutti, R. and Mauritsen, T. and Norris, J. R. and Proistosescu, C. and Rugenstein, M. and Schmidt, G. A. and Tokarska, K. B. and Zelinka, M. D.},
  title={An assessment of Earth's climate sensitivity using multiple lines of evidence},
  year={2020},
  journal={Rev. Geophys.},
  doi={10.1029/2019RG000678},
  note={Manuscript accepted for publication}
}

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RIS Citation

TY  - INPR
ID  - sh02800e
AU  - Sherwood, S.
AU  - Webb, M. J.
AU  - Annan, J. D.
AU  - Armour, K. C.
AU  - Forster, P. M.
AU  - Hargreaves, J.
AU  - Hegerl, G.
AU  - Klein, S. A.
AU  - Marvel, K. D.
AU  - Rohling, E. J.
AU  - Watanabe, M.
AU  - Andrews, T.
AU  - Braconnot, P.
AU  - Bretherton, C.
AU  - Foster, G. L.
AU  - Hausfather, Z.
AU  - von der Heydt, A. S.
AU  - Knutti, R.
AU  - Mauritsen, T.
AU  - Norris, J. R.
AU  - Proistosescu, C.
AU  - Rugenstein, M.
AU  - Schmidt, G. A.
AU  - Tokarska, K. B.
AU  - Zelinka, M. D.
PY  - 2020
TI  - An assessment of Earth's climate sensitivity using multiple lines of evidence
JA  - Rev. Geophys.
DO  - 10.1029/2019RG000678
ER  -

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