The transient climatic response and the detection of anthropogenic effects on climate

In the preceding chapter we examined the regional patterns of steady-state climatic change following a doubling of atmospheric CO₂, as simulated by AGCMs coupled to simple, mixed layer-only ocean models. A CO₂ doubling was used as a surrogate for the actual combination of GHG concentration changes giving rise to the same global mean forcing as for a CO₂ doubling. Since the focus in these experiments was on steady-state climatic changes, there was no need to consider the delay in surface warming caused by the mixing of heat into the deep ocean. To reduce the computational cost further, the models were subjected to a sudden doubling of the CO₂ concentration once a steady-state climate with the present (or near-present) CO₂ concentration had been reached.