Most European countries have signed the United Nations Framework Convention on climate change and its Kyoto Protocol. Because the European Union is a party to the convention just like the individual countries, there is a need for harmonizing emissions reporting. This specifically applies
to the Land Use, Land-Use Change, and Forestry sector, for which harmonized reporting is complex and generally challenging. For example, parties use a variety of different methods for estimating emissions and removals, ranging from application of default factors to advanced methods adapted
to national circumstances, such as ongoing field inventories. In this study, we demonstrate that without harmonization, national definitions and methods lead to inconsistent estimates. Based on case studies in Finland, Germany, Norway, Portugal, Slovenia, and Sweden, we conclude that common
reference definitions and country-specific bridges are means to harmonize the estimates and make greenhouse gas reporting from forests comparable across countries.