Recent studies have suggested that the combined effect on climate of increases in the concentrations of several trace gases (principally CH4 and N2O) could rival or even exceed that of the increasing concentration of carbon dioxide (CO2), due to their much stronger abilities in absorbing infrared radiation. Despite their high potential for climate feedback, the specific sources, magnitudes and changes of these trace-gas emissions are still not well understood. Since the state and amount of water in the soil is a key player in modulating these emissions, the project proposes to use the unprecedented global high-resolution land surface soil moisture and freeze/thaw state from the Soil Moisture Active Passive (SMAP) product together with other land-based observations to improve the performance of the Community Land Model’s (CLM) soil moisture simulations, enhance the N2O and CH4 modules and thereby reduce uncertainties in the emission estimates over a majority of the Earth’s land surfaces. These anticipated improvements will ultimately support greater confidence in assessing the fate of various key trace-gas emissions and the relative contributions of these natural emission changes (separate and combined) to the climate feedbacks under various climate-change scenarios.