Precision and uncertainty in emissions calculation models

This Explainer report covers the context and concepts of Greenhouse Gas (GHG) accounting and emission calculation model precision, uncertainty, and materiality. It shows:

• There is a difference between measuring and modelling greenhouse gas (GHG) emissions. Whilst measuring determines the exact amount of GHG emitted, modelling is a simplification of measuring physical processes.
• A model requires a single variable activity data multiplied by an emissions factor (EF).
• Emission factors help us understand the level of greenhouse gases intensity that occurs from certain activities. They have a certain level of accuracy and uncertainty.
• Toitū sources or develops emission factors additional to those published by government agencies, including to improve accuracy.
• Carbon accounting might not give a precise representation of GHGs being emitted, but it does equip organisations with vital insights into their climate impact and areas of influence. If it isn’t measured, it cannot be managed.

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