One of major challenges facing Earth's science in the nextdecade and beyondis the development of an accurate longterm observational data set to study global change. Toaccomplish this, a wide range of observations will berequired to provide both new measurements, not previouslyachievable and measurements with a greater degreee ofaccuracy and resolution than the ones which are presentlyand currently available.Among the parameters that are currently retrieved fromsatellite vertical sounding observations, temperature andmoisture profiles are the most important for the descriptionof the thermodynamic state of the medium. Other parameters,like those describing the cloud fields, the surface state orthe conditions close to the surface are also key parametersfor meteorology and climatology.A new generation of high spectral atmospheric sounders inthe infrared has recently been designed to provide both newand more accurate data about the atmosphere, land and oceansfor application to climate studies. Among the importantobservations that these instruments should contribute to theclimate data set are day and night global measurements of:atmospheric temperature profiles; relative humidityprofiles; cloud field parameters; total ozone burden of theatmosphere; distribution of minor atmospehric gases(methane, carbonmonoxide and nitrous oxide).