The World Climate Research Program (WCRP) has provided the scientific incentive for a very significant step forward in the development of global oceanic observations, especially the preparation of a new generation of oceanographic satellites that will sense the topography of the mean sea surface, wind stress, sea state, and temperature . On the other hand, progress in understanding the atmospheric and interface processes that control Earth's climate has been based, so far, on information provided by existing global observing systems. These are, to a large extent, the operational heritage of the technological developments undertaken on the occasion of the Global Atmospheric Research Program (GARP) Global Weather Experiment. These observing systems were designed to determine the basic quantities of dynamic meteorology, atmospheric pressure, temperature, and wind, with the main objective of developing global weather prediction. It is only through the use of ad hoc procedures and empirical schemes that additional information can be inferred from these observations to estimate essential climate-related quantities such as the cloud cover, radiative fluxes, and rainfall. These ad hoc schemes have limitations that are now seriously hampering further advances in the understanding of the dynamics and thermodynamics of the climate system.