Pulse response functions are cost-efficient tools to model the link between carbon emissions, atmospheric CO2 and global warming

Abstract The development of models to simulate the redistribution of anthropogenic carbon and the climate response to greenhouse gas forcing requires a substantial effort. The behavior of such models can be characterized by pulse response functions which allows one to build simple substitute models. We have used mixed-layer pulse response functions to describe the surface-to-deep mixing of tracers in the ocean and biospheric decay response functions to describe carbon turnover in the land biota. We build a simple carbon cycle-climate model using response functions. For the Princeton-GFDL ocean model, we find that the agreement between the complete model and its pulse substitute model is better than 4% for the cumulative uptake of anthropogenic carbon applying the IPCC stabilization scenarios S450 and S750. We have simulated the transient temperature response to an increasing CO2 concentration (1% yr−1) prescribing climate sensitivities of 2.1 and 4.6 K for a CO2 doubling in the substitute model. We find a global surface temperature warming of 1.6 and 2.4 K after 80 years in good agreement with the corresponding results (1.5 to 2.7 K) of 9 atmosphere-ocean general circulation models (Houghton et al., 1996). The pulse model is efficient; a 1000 year simulation of the pulse substitute model requires 25 seconds of CPU time on a workstation.