Carbon Climate Interactions (Invited Presentation)

In the first Coupled Climate Carbon Cycle Model Intercomparison Project (C⁴MIP), anthropogenic CO₂ emissions are specified in global climate model integrations, and the concentrations of radiative CO₂ are predicted as the residual in the global carbon budget, after the climate- and CO₂-sensitive land and oceans sinks have been accounted for. The C⁴MIP results, included in the IPCC 4th Assessment Report, show that the capacities of the land and oceans to absorb CO₂ decrease with warming despite higher atmospheric CO₂. Carbon-climate feedbacks are thus positive and act to accelerate the warming. IPCC AR5 specifies the CO₂ trajectory, and infers the concomitant trajectory of “allowable emissions”. Jay Fein shepherded the first incorporation of an interactive carbon cycle into the NCAR global climate model CSM1 and enabled the development and growth of Earth System Models.