The climate of the Earth is intimately tied to the composition of the atmosphere and the dynamics of the underlying surface. The atmosphere and land surface exchange energy, water and other trace substances on all space and time scales. The exchange is dependent on, and in turn determines, the states of the atmosphere and biosphere themselves. Our research in the past decade has focused on the processes that maintain and alter climate, as well as on the biogeochemical cycling of carbon dioxide, methane and dust. The goal is to gain predictive capability of how atmospheric composition and climate have evolved in the past and may co-evolve in the future.The present and past variations in atmospheric composition contain information about how sensitive the atmosphere and biosphere are, separately and together, to natural climate fluctuations. This sets the stage for detecting and evaluating the extent to which the systems have been and will be altered by human action.