Sensitivity of the LMD general circulation model to greenhouse forcing associated with two different cloud water parameterizations

The atmospheric general circulation model is coupled to a slab ocean model and is used to investigate the climatic impact of a CO₂ doubling. Two versions of the model are used with two different representations of the cloud-radiation interaction. The annual and global mean of the surface warming is similar in the two experiments in spite of regional differences. The results show that, in the second model version, the cloud feedback decreases significantly, especially at high latitudes, due to an increase of low-level clouds in the 2 × CO₂ simulation. The modification of the cloud scheme influences also the water vapor variation and the associated feedback is reduced, in particular, over the subtropical regions. -from Authors