(eng): In the present study, we use direct comparisons between the CrIS (Cross-track Infrared Sounder ) observations and model retrievals using the Least Squares with Adaptive Prior Covariance (LS-APC) algorithm, which reduces the number of tuning parameters in the method significantly using variational Bayes approximation technique. We constrain ammonia emissions over Europe over 2013–2020 and validate the results against ground-based observations from the EMEP (European Monitoring and Evaluation Programme). We find that emissions of ammonia decreased from 5431 Gg in 2013 to 3994 Gg in 2020 (-26%). Regionally, emissions declined by 38% in Central and Eastern Europe, 37% in Western Europe, 8% in Southern Europe and -17% in Northern Europe.