21 January 2019

Evaluation of Proposed Emergent Constraints on Climate Sensitivity

The credibility of 19 previously-proposed emergent constraints is evaluated using a new methodology.


A new method is developed for assessing the credibility of current-climate predictors of climate change (aka emergent constraints). Using this approach, 19 previously-proposed constraints are evaluated.


Emergent constraints are an important and popular method for predicting future climate change. This paper is the first to provide a broad intercomparison of previously-proposed emergent constraints and provides a novel technique for evaluating the trustworthiness of these constraints.


Emergent constraints are present-day observable quantities with skill at predicting future climate change. They have become important tools for climate prediction, but it is hard to say how much trust to put in these predictions. One measure of the credibility of emergent constraints is whether its physical explanation is compelling. In this paper, we provide a new technique for identifying which aspect of the climate system (clouds, surface albedo, etc) is responsible for an emergent constraint's predictive skill. Constraints whose actual predictive skill differs from their theoretical explanation are of dubious credibility. This technique is used in an intercomparison of 19 previously-proposed emergent constraints for climate sensitivity.

Peter Caldwell
Lawrence Livermore National Laboratory
Caldwell, P, M Zelinka, and S Klein.  2018.  "Evaluating Emergent Constraints on Equilibrium Climate Sensitivity."  Journal of Climate 31(10): 3921-3942, doi:10.1175/jcli-d-17-0631.1.