Greenhouse gas Abatement Cost Model (GACMO)

Calculating current and future greenhouse gas emissions is a prerequisite for countries to inform political decisions concerning climate action. It is also the foundation for transparent and credible climate action at national and global levels.

The GACMO (Greenhouse Gas Abatement Cost Model) is a greenhouse gas emissions projections tool developed over more than twenty years by the UNEP Copenhagen Climate Centre.

It allows countries to carry out rapid but accurate scenario analysis of how a variety of mitigation options impact emissions, thereby increasing transparency and contributing to informed decision making.

The tool can provide valuable input for preparing and updating NDCs by identifying NDC targets for emissions reductions and by providing assessments of future emissions in different climate action scenarios. It can also be used to prepare biennial transparency reports (BTRs) under the Paris Agreement.

The GACMO tool can be downloaded and used free of charge.

The tool is regularly updated. The last version of the GACMO tool is always made available on this webpage.

A new version of the GACMO tool (version 2.2) is now available as of March 2025. This new version follows the same methodological approach as the previous GACMO versions. The version 2.2 includes the following changes:

1. An additional Step 9 “Results in BTR format” was added. This new Step 9 includes two tables identical to the CTF Tables of the Biennial Transparency Report, namely CTF Tables 7 (Projections in scenario with measures) and CTF Table 9 (Projections in scenario without measures). GACMO automatically converts the results from the “Results” sheet and automatically filled in the two tables of the “Results BTR” sheet.
2. A revised sectoral disaggregation in the emissions data for the start year and projected years (Step 3 and Step 6). The revised disaggregation is now defined so that the categories are identical to the categories of the Common Reporting Tables (CRT) agreed upon by the Parties to the Paris Agreement. These changes have been made to align the GACMO input tables and output results with the IPCC inventory categories.
3. A disaggregation of the projections by gases: CO2, CH4, and N2O in kilotonnes of CO2 equivalent.
4. New results tables in Step 8 (“Results” sheet) incorporating total GHG emissions projections with and without LULUCF, as well as total GHG emissions projections by sectors and by sub-sectors (in line with CRT) and by gases.

The GACMO version 2 has been developed with the support of the Initiative for Climate Action Transparency (ICAT).

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