Thus, there seem to be a lot of assumptions about ocean heat uptake which lead to the unsupported conclusion that there is «
rapid equilibration of the climate system to applied forcings».
(This behavior is, I think, associated with a relatively
rapid cycling and
equilibration between the atmophere and upper ocean, a slower
equilibration with vegetation, and a slower
equilibration with the deep ocean (and there's
equilibration with exposed carbonates);
equilibration with each successive C reservoir still leaves some of the atmospheric perturbation because the C is just being redistributed over a larger total reservoir (PS not necessarily maintaining the same equilibrium ratios, though I don't know about that much offhand).