Climate & Environment
Tier 1/2/3 Method
Definition
The tier structure is the IPCC's graded approach to greenhouse gas inventory methods: Tier 1 applies default emission factors to basic activity data; Tier 2 uses country- or region-specific factors for key categories; Tier 3 uses facility-level data and detailed models or direct measurement. Higher tiers reduce uncertainty but demand more data and capacity, and good practice requires higher tiers for a country's key (largest or fastest-growing) source categories.
References
This reference provides supporting context for how “Tier 1/2/3 Method” is defined and used.
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Overview
How it is used
The structure structures national inventory compilation, UNFCCC technical review, capacity building priorities and the design of monitoring protocols in carbon markets.
Why it matters
Tiered methods are the reason universal reporting is possible — the ladder that lets every country onto the same accounting system.