Our previous study has shown that cloud plays much more important roles on the surface dimming/brightening trends. Aerosol direct radiative effects is only obvious under clear sky conditions. Big questions need to be addressed: (1) What causes the cloud trend? (2) How much is the change of cloud mediated by aerosols through aerosol-cloud-radiation interaction? (3) How does climate change affect the cloud and aerosol trends and their interactions? This proposed ACRI study is to answer the above questions through a set of GCM model experiments described here: A3_ACRI_2019-01-21.pdf