The Earth System is

The Earth System is the unified set of physical, chemical, biological and social components, processes and interactions that together determine the state and dynamics of Planet Earth, including its biota and its human occupants.

Earth System Science is the study of the Earth System, with an emphasis on observing, understanding and predicting global environmental changes involving interactions between land, atmosphere, water, ice, biosphere, societies, technologies and economies.
http://www.essp.org/
Earth System Science Partnership (ESSP)
The ESSP is a partnership for the integrated study of the Earth System, the ways that it is changing, and the implications for global and regional sustainability.

The urgency of the challenge is great: In the present era, global environmental changes are both accelerating and moving the earth system into a state with no analogue in previous history.

To learn more about the ESSP, clink on links to access Strategy Paper and a video presentation by the Chair of the ESSP Scientific Committee, Prof. Dr. Rik Leemans of Wageningen University, The Netherlands.