The Greenhouse Gases from Agriculture Simulation Model (GreenAgSiM) presented in this paper aims to quantify emissions from agricultural activity on a global scale. The model takes emissions into account that are directly attributable to agricultural production, such as enteric fermentation (methane), manure management (methane and nitrous oxide), and agricultural soil management (nitrous oxide). Furthermore, carbon stock differences from land-use change (carbon dioxide) induced by agriculture are included in the model. The model will provide policy makers with information about the greenhouse gas implications of policy changes.