In a career that spans over four decades, Robert D. Cess has pioneered the study of diverse topics and disciplines. He first attacked problems dealing with conductive, convective, and radiative heat transfer in engineering systems and his contribution to these topics culminated in a classic text book on radiative transfer. The hallmark of this early work is the successful application of singular peturbation techniques to solve complex radiative heat transfer problems. His intellectual curiosity took him to the study of thermal structure of planetary atmospheres. He is one of the very select few (if not the only one) who has solved the thermal structure of almost all of the inner and outer planets of the solar system including Mercury, Mars, Earth, Venus, Jupiter, Saturn, and others, including study of the satellites. He was probably the first to obtain an analytical solution for the radiative-convective equilibrium-temperature structure of the troposphere-stratosphere of Mars and Venus.

The latter part of his career has been focused exclusively on Earth, where he has made fundamental contributions to our understanding of the physics of climate with a particular focus on processes that regulate the Earth's radiation budget and the mechanisms of cloud feedback processes. He obtained worldwide recognition for a comprehensive comparative study of the nature of water-vapor and cloud feedback processes of over 15 three-dimensional climate models, and brilliantly demonstrated that cloud feedback is the major source for the wide range in climate sensitivity of climate models.