Uncertainty on low cloud cover feedback is the primary contributor to the spread of equilibrium climate sensitivity in climate models. Although most climate models predict a decreasing low cloud cover under long-term global warming, the ensemble of atmospheric models suggests that low cloud cover has increased during 1980-2008. Idealized experiments suggest that this difference is caused by the difference of SST warming pattern on the two timescales. The low cloud cover trend during the last three decades is likely to contribute to the recent global warming hiatus.

This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.