The Intergovernmental Panel on Climate Change (IPCC) has issued "Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories" (IPCC, 2000). In this report IPCC distinguishes two levels of comprehension for quantitative uncertainty assessment in emissions monitoring, which they named TIER 1 and TIER 2. TIER 1 uses the error propagation equation (Mandel 1984, Bevington and Robinson 1992) to estimate error propagation in calculations whereas TIER 2 consists of a full Monte Carlo analysis. Since this influential report, the method using the classic analytical equations for error propagation (well known by most students of the experimental sciences) has now become widely referred to as the 'TIER 1' approach.