The Greenhouse Gas Protocol Initiative: Measurement and Estimation of Uncertainty of GHG Emissions
The Greenhouse Gas Protocol Uncertainty Tool is designed to facilitate a quantitative and qualitative estimation of uncertainty associated with a GHG inventory. The tool aggregates statistical parameter uncertainties associated with the calculation of GHG emissions. The methodologies embedded in the tool are based on the Greenhouse Gas Protocol developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). This calculator can be used facilitate an assessment of the quality of a GHG emissions baseline and/or annual emissions inventory.
Inputs and Outputs
Inputs include: For each indirectly measured emissions source, the user must input the activity data (e.g., gallons of fuel consumed or kWh of electricity purchased) and the emission factor associated with that data. The tool also requires the user to assign an uncertainty range (e.g., +/-10%) with both the activity data and the emission factor.
For each directly measured emissions source, the user must input the estimated GHG emissions and the estimated uncertainty range associated with those emissions calculations.
Outputs include: The tool can be used to estimate uncertainty associated with both indirectly and directly measured emissions. Based on user inputs, the tool automatically calculates the uncertainty range (e.g., +/- 15%) associated with each emission source as well as an aggregated uncertainty measurement associated with the entire inventory as a whole. Similarly, both the individual and aggregated emissions sources are automatically assigned a qualitative uncertainty ranking (e.g., High, Good, Fair, and Poor) based on the quantitative uncertainty range.
The GHG Protocol Uncertainty Tool can be used in conjunction with other WRI tools (e.g., the GHG Protocol tools for stationary combustion and purchased electricity), or in conjunction with other non-WRI tools that a community might use to develop a GHG inventory. The tool is accompanied by a detailed guidance document, "GHG Protocol guidance on uncertainty assessment in GHG inventories and calculating statistical parameter uncertainty"  This document provides instructions on using the tool along with guidance on the different types of uncertainty associated with a GHG inventory. Additionally, the guidance document provides detailed information on collecting uncertainty data and interpreting the results of an uncertainty assessment.
This tool represents one of the Greenhouse Gas Protocol Initiative's several cross-sector spreadsheets that can be used separately or in conjunction to develop a GHG inventory of various emissions sources within a community. Separate calculators are available for emissions from purchased electricity, stationary combustion, mobile combustion, refrigeration and air conditioning equipment, and several industrial sectors.