COST, The Terrestrial Biosphere in the Earth System (TERRABITES) https://www.cost.eu/actions/ES0805/. The main objective of the Action is a cross-disciplinary assessment of our current understanding of the terrestrial biosphere from an Earth system perspective to improve the reliability of future Earth system projections in coupled climate-biosphere simulations. Key words: earth system modeling – terrestrial biosphere – climate projections – remote sensing – global change.