Uncertainties in the Finnish 2001 Greenhouse Gas Emission Inventory

This study is a part of Finland's Greenhouse Gas Emission Inventory work to the United Nations Framework Convention on Climate Change (UNFCCC). Reliable uncertainty estimates are required by the UNFCCC, and they also function as a tool for increasing the quality of national emission inventories. Uncertainty in emission estimates can arise from inaccuracy in emission monitoring, lack of knowledge involving the emission factor and activity data estimates, or, for example, biased expert judgement. The quality of emission inventories for the most important greenhouse gas, CO2, depends mainly on the accuracy of fuel use statistics. Some other sources of CO2, and the other greenhouse gases of the Kyoto Protocol, CH4, N2O, HFCs, PFCs and SF6, are usually rather poorly known. This is the first time Tier 2 uncertainty assessment is used for the Finnish Greenhouse Gas Emission Inventory. For the purpose of this report it was performed concerning the years 1990 and 2001. This report presents the basis of each input parameter uncertainty estimate which were mainly based on available measurement data, domestic and international literature, expert judgement and the recommendations of the Intergovernmental Panel on Climate Change (IPCC). Uncertainty estimates of different sources were combined using Monte Carlo simulation, which allows the use of asymmetrical distributions and flexible handling of correlations. The resulting total uncertainty in the 2001 emissions was -5...+6%. The asymmetry results from highly uncertain emission sources that have asymmetrical distributions. The trend uncertainty (change between 1990 and 2001) was assessed to ±5%-points. The most significant sources contributing to the total uncertainty were identified with sensitivity analysis and key source identification. The most important emission sources affecting the total uncertainty are CO2 emissions from arable peatlands and peat production areas, and N2O emissions from agricultural soils.