Earth observations for earth system science : contextual overview

Since the early days of space exploration it was realised that space provided a unique vantage point for observing the earth as a system. Earth system science was formally initiated by NASA between 1983 and 1986 with the goal of 'obtaining a scientific understanding of the entire earth system on a global scale by descriptionbing how its components and their interactions have evolved, how they function, and how they may be expected to continue to evolve on all timescales'. At the highest level, the four basic elements of the earth system can be represented as air (atmosphere), water (hydrosphere), land (geosphere) and life (biosphere, including human activities).