Introduction and reporting requirements

The global protocol for community-scale greenhouse gas inventories (GPC), version 1.1 sets a standardised framework for cities to measure and report greenhouse gas (GHG) emissions. It supports the creation of base year inventories, target setting, tracking over time, and alignment with national data. The updated version reflects 2019 IPCC refinements and clarifies previous guidance.

Accounting and reporting principles

Inventories must follow five key principles: relevance, completeness, consistency, transparency, and accuracy. Data gaps must be identified using notation keys such as NO (Not Occurring) or NE (Not Estimated), with explanations provided.

Setting the inventory boundary

Cities define their inventory boundary by geography and time, typically one year. Emissions are grouped into six sectors and categorised as scope 1 (within boundary), scope 2 (grid-supplied energy), and scope 3 (outside boundary but city-induced). Scope 1 data supports national-level aggregation.

Reporting requirements

Emissions must be reported by gas, scope, sector, and subsector using two frameworks: scopes and city-induced. BASIC covers scope 1 and 2 from energy and transport, and scope 1 and 3 from waste. BASIC+ includes IPPU, AFOLU, and transboundary transport. Annual updates and data quality assessments are recommended.

Calculation guidance by emission source

Emissions are calculated by multiplying activity data by emission factors. Cities should use local or country-specific data where possible. Emissions are reported in CO₂ equivalents using 100-year global warming potential (GWP). Data and methodology must be documented, and quality rated.

Stationary energy

This includes fuel combustion and fugitive emissions from buildings, industry, and energy supply. scope 1 covers direct combustion, scope 2 includes grid energy use, and Scope 3 accounts for distribution losses. Emissions must be categorised by sub-sector, with further detail encouraged for mitigation planning. Waste-to-energy and district energy systems must be reported accurately, avoiding double counting.

Transportation

Covers emissions from on-road, rail, aviation, water, and off-road transport. BASIC includes Scope 1 combustion and scope 2 electricity use. BASIC+ adds transboundary journeys (scope 3). Cities may use top-down or bottom-up methods based on data availability.

Waste

Emissions arise from solid waste disposal and wastewater treatment. Cities must report based on treatment method and location. scope 1 includes local treatment; scope 3 covers exported waste. Biogenic CO₂ must be reported separately.

Industrial processes and product use

Emissions result from non-energy industrial processes and product use (e.g. refrigerants). These fall under scope 1. Cities should use IPCC categories and report delayed emissions from products where relevant.

Agriculture, forestry and other land use

Covers emissions and removals from livestock, land use change, and fertiliser application. Categories follow IPCC guidance. Where removals occur, these may be reported separately or netted.

Setting goals and tracking emissions over time

Cities may adopt base year, fixed-level, intensity, or scenario targets. Emissions must be tracked consistently. Recalculations are needed if boundary or method changes occur.

Managing inventory quality and verification

Verification is not required but encouraged. Cities should document processes and assess completeness and accuracy. Verification may be internal or external and helps improve data credibility.