The uptake of heat and carbon is examined in an ensemble of runs using an Earth System Model of intermediate complexity. Climate model “parameters” varied to produce the ensemble are the climate sensitivity, the aerosol forcing, and the strength of ocean background diapycnal mixing. Joint probability distributions for climate sensitivity and aerosol forcing are constructed by comparing climate model results from 20th century simulations with available observational data. The results from the 21st century ensemble allows us to construct probabilistic distributions for changes in important climate change variables such as surface air temperature, sea level rise, magnitude of the meridional overturning circulation, air-sea fluxes of carbon, distribution of nutrients, and the export of carbon to the deep ocean. We use the different dynamical and thermal structures of the ensemble members as a tool to explore the controls on and the uncertainty in heat and carbon uptake.