Diversity and uncertainty in the assessment of GHG emissions in national inventories: a sectoral analysis of Northeastern European countries

The correlation between estimated national GHG emissions and uncertainty is generally known. The causes and sources of the uncertainties are diverse and relate to source activity (field studies and research, census data), methodologies, variations in emission factors, and scientific studies/publications. Uncertainty has occurred due to a lack of knowledge of true values, in which uncertainty is assessed by the probability density function. Uncertainty analysis helps identify and prioritize activities (monitoring, inventory, evaluation methods, etc.) to improve the evaluation and reduce uncertainty. A quantitative uncertainty analysis is often performed for a 95% confidence interval. 
Different calculation methodologies are used in each sector (waste, energy, LULUCF, industry, transport, and agriculture); the mechanisms for producing emissions of emitted substances are complex and variable and require scientifically based research to update them. Regional differences are also essential, as climate, access to technologies, the possibility of introducing them, and other physio-geographic conditions have a significant impact. One of the challenging issues in the GHG emissions assessment relates to future emission projections related to future unpredictability due to climate change; changes in economic growth plans also create a lot of uncertainty. For example, in the forest management and land use sectors, the intensity of CO₂ sequestration in the ecosystem must be assessed. Recent studies, including those informing Latvia's LULUCF emission factors, reveal significant uncertainties in estimating GHG emissions from organic-rich soils due to short-term measurements, limited sampling, and neglect of long-term soil carbon dynamics.  Another relatively more straightforward source of data uncertainty is identified in the waste management sector. In this sector, the analysis of methane emissions from landfills from disposed solid municipal waste requires a precise morphological composition of the waste, as the result of the calculation depends not only on the amount of waste but also on the content of organic matter and the intensity of aerobic or anaerobic degradation. It is self-evident that the composition of waste can be variable and monitored effectively today. Still, different waste fractions are characterized by different degradation intensities, and according to the assessment method, degradation should be assessed over a period of 100 years, which means that the historical morphological composition of waste is required. The lack of such data often leads to up to 150 % uncertainty. 
When analyzing the national reports of the Northeastern Region of Europe (Latvia, Finland, Estonia, and Lithuania), the most considerable uncertainties can be found in the LULUCF sector, which, in view of these countries' economic activities, is very substantial in the overall assessment. Reducing uncertainty in this area is of the utmost importance as it is closely linked to national climate plans and the measures taken to achieve climate neutrality.