The present document provides methodology for assessing environmental impact of AI systems. The methodology is based on Life Cycle Assessment (LCA) methodology standardized in [ITU-T L.1410/ETSI ES 203 199] and method for enabling effects for other sectors standardized in [ITU-T L.1480/ETSI ES 204 087]. The guidance in the present document focuses on AI system specific aspects which need to be taken into account in the assessment. Aggregation of AI impact on international, national or regional level is not part of the present document.