There are two important related areas of research in atmospheric radiation that have progressed significantly through the early 1990's. One area focuses on the use of radiation measurements, such as obtained from satellite sensors, to obtain vital information about the global climate system. The other area of activity exploits these data to carry out diagnostic studies of climate, to attempt to verify climate model performance, to examine key feedbacks of the climate system and to identify possible new feedback mechanisms. Much of this work has been centered on the role of clouds in climate and the study of cloud--radiation interactions underpins this research.