Abstract. Volatilization of ammonia (NH3) from fertilizers and livestock wastes forms a significant pathway of nitrogen losses in agricultural ecosystems, and constitutes the largest source of atmospheric emissions of NH3. This paper describes a major update to the process model FAN (Flow of Agricultural Nitrogen), which evaluates the NH3 emissions interactively within an Earth system model; in this work, the Community Earth System Model (CESM) is used. The updated version (FANv2) includes a more detailed treatment of both physical and agricultural processes, which allows the model to differentiate between the volatilization losses from animal housings, manure storage, grazed pastures, and from application of manure and different types of mineral fertilizers. FANv2 is connected to the interactive crop model within the land component of CESM, which determines the amount and timings of fertilizer applications for major types of crops. The model is first evaluated at local scale against experimental data for various types of fertilizers and manure, and subsequently run globally to evaluate present-day NH3 emissions. Comparison of regional emissions shows that FANv2 agrees with previous inventories for North America and Europe, and is within the range of previous inventories for China. However, due to higher NH3 emissions in Africa, India and Latin America, the global emissions simulated by FANv2 (47 Tg N) are 30–40 % higher than in the existing inventories.;
