The most abundant alkaline compound in the atmosphere is ammonia (NH3). NH3 neutralizes acids and contributes to the formation of aerosols and particulate matter, with consequences to the environment, human health, and radiative forcing. NH3 is primarily emitted by agricultural activities, livestock, natural sources, fertilizers, and biomass burning, and it is present in urban and remote environments. NH3 emissions and depositions strongly depend on environmental conditions such as temperature and moisture. NH3 has a short lifetime on the order of hours to a few days and exhibits a strong temporal and spatial variability. In this talk, first I will present the temporal variability and trends of NH3 from 16 ground-based FTIR (Fourier Transform InfraRed) sites, classified as urban or remote,  dispersed in both hemispheres from 45° S to 80° N, most of the sites are part of the  Network for Detection of Atmospheric Composition Change (NDACC). In addition, I'll show comparisons between the NH3 total columns from the FTIR instruments and from two different chemical transport models. Finally, I'll present some conclusions and future work.