The major research thrusts of ESSIC are studies of Climate Variability and Change, Atmospheric Composition and Processes, the Global Carbon Cycle (including Terrestrial and Marine Ecosystems/Land Use/Cover Change), and the Global Water Cycle. The manner in which this research is accomplished is via analyses of in situ and remotely sensed observations coupled with ocean-atmosphere-land models. Together this provides a foundation for understanding and forecasting changes in the global environment and regional implications. Data assimilation and regional down-scaling provide the means by which the observations and models are linked to study the interactions between the physical climate system and biogeochemical cycles from global to regional.