Séminaire
The regional manifestations of global climate change depend on the response of the large-scale atmospheric circulation. Recent work showed that a substantial part of future circulation changes results from clouds and their radiative interactions, and highlighted the role of shortwave cloud-radiative interactions from low-level clouds. Here, we manipulate clouds in a hierarchy and an ensemble of global climate models to identify another important mechanism involving longwave radiative interactions of high-level ice clouds. We find that this mechanism contributes, depending on the model, half or more to the poleward circulation expansion, and to first order arises from the upward shift of high-level ice clouds and the associated radiative heating in the upper troposphere. This heating is related to present-day clouds and scales with the magnitude of global-mean surface warming, providing an opportunity to constrain it from observations.
marie-pierre.lefebvre@lmd.jussieu.fr