An assessment of the primary sources of spread of global warming estimates from coupled atmosphere-ocean models.

Jean-Louis Dufresne (1) , Sandrine Bony (1)

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

Climate feedback analysis constitutes a useful framework to compare the global mean surface temperature responses to an external forcing predicted by general circulation models (GCMs). Nevertheless, the contributions of the different radiative feedbacks to global warming (in equilibrium or transient conditions) and their comparison with the contribution of other processes (e.g. the ocean heat uptake) have not been quantified explicitly. Here we define these contributions from the classical feedback analysis framework, and we quantify them for an ensemble of 12 CMIP3/IPCC-AR4 coupled atmosphere-ocean GCMs. In transient simulations, the multi-model mean contributions to global warming associated with the combined water vapor - lapse rate feedback, cloud feedback and ocean heat uptake are comparable. However, inter-model differences in cloud feedbacks constitute by far the primary source of spread of both equilibrium and transient climate responses simulated by GCMs. The spread associated with inter-model differences in cloud feedbacks appears to be roughly three times larger than that associated either with combined water vapor - lapse rate feedback, the ocean heat uptake or the radiative forcing.

Domaines: Océan, Atmosphère

Jean-Louis Dufresne, Sandrine Bony. An assessment of the primary sources of spread of global warming estimates from coupled atmosphere-ocean models.. Journal of Climate, 2008, 21 (19), pp.5135-5144. ⟨10.1175/2008JCLI2239.1⟩. ⟨hal-00423479⟩