Satellite and surface observations are used to document decadal variations in tropical cloud cover and radiation flux along with associated spatial patterns. Sea surface temperature and reanalysis dynamical parameters are examined to understand how the cloud variations are related to changes in atmospheric structure and circulation. In particular, 46-year trends in upper-level cloud cover resemble the interannual response to the warm phase of ENSO. Output from the Community Climate System Model Version 3 run with and without historical anthropogenic and natural forcing is examined to see whether similar decadal cloud and radiation variations occur and whether they can be attributed to internal variability or a response to external forcing.