Steady-state and transient dynamic behavior of simple climate models for application in integrated assessment models

We characterize the steady-state and transient dynamic behavior of a suite of twelve linear time-invariant (LTI) climate models capturing the response of global mean surface temperature to net radiative forcing. The LTI models considered here have previously been obtained by system identification experiments with data derived from the Coupled Model Intercomparison Project phase 3 (CMIP3), and have subsequently been applied in integrated assessment models (IAMs) of climate-economy based on the solution of a finite-horizon nonlinear optimal control problem, where atmosphere-ocean general circulation models (AOGCMs) of the climate are computationally prohibitive. In this paper, we compute the equilibrium climate sensitivity (ECS) and transient climate response (TCR) for each of the twelve LTI climate models in the model suite, and compare the values so obtained with previously published values of ECS and TCR for these CMIP3 models. The results of this paper confirm the suitability of simple LTI climate models in IAMs, and validate the robustness of conclusions drawn from the application of such models in integrated climate-economy assessments.