06 Oct 2022
06 Oct 2022

Better constrained climate sensitivity when accounting for dataset dependency on pattern effect estimates

Angshuman Modak and Thorsten Mauritsen Angshuman Modak and Thorsten Mauritsen
  • Department of Meteorology, Stockholm University, Stockholm, Sweden

Abstract. Equilibrium climate sensitivity (ECS) constrained based on the instrumental record of the historical warming becomes coherent with other lines evidence when the dependence of radiative feedbacks on the pattern of surface temperature change (pattern effect) is incorporated. Pattern effect strength is usually estimated with atmosphere-only model simulations forced with observed historical sea-surface temperature (SST) and sea-ice change, and constant pre-industrial forcing. However, recent studies indicate that pattern effect estimates depend on the choice of SST boundary condition dataset, due to differences in the measurement sources and the techniques used to merge and construct them. Here, we systematically explore this dataset dependency by applying seven different observed SST datasets to the MPI-ESM1.2-LR model covering 1871–2017. We find that the pattern effect ranges from -0.01 ± 0.09 Wm-2 K-1 to 0.42 ± 0.10 Wm-2 K-1 (standard error), whereby the commonly used AMIPII dataset produces by far the largest estimate. When accounting for the generally weaker pattern effect in MPI-ESM1.2-LR compared to other models, as well as dataset dependency and inter-model spread, we obtain a combined pattern effect estimate of 0.30 Wm-2 K-1 [-0.14 to 0.74 Wm-2 K-1] (5–95 percentiles) and a resulting instrumental record ECS estimate of 3.1 K [1.7 to 9.2 K], which is slightly lower and better constrained than in previous studies.

Angshuman Modak and Thorsten Mauritsen

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-976', Anonymous Referee #1, 03 Nov 2022
  • RC2: 'Comment on egusphere-2022-976', Tim Andrews, 11 Nov 2022

Angshuman Modak and Thorsten Mauritsen

Angshuman Modak and Thorsten Mauritsen


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Short summary
We estimate Equilibrium Climate Sensitivity, a metric to constrain future global warming based on the instrumental temperature record including the corrections for the effects on radiation balance caused by the pattern of surface temperature change- pattern effect. We address the uncertainty caused by the underlying sea surface temperature datasets used in the estimates of pattern effect. This together with the intermodel spread lifts the corresponding IPCC AR6 estimate to 3.1 K [1.7 to 9.2 K].