Data Provenance

Overview

co2e bundles three lookup tables (gwp_values, gases, gas_synonyms), built from a small set of source files in data-raw/. This vignette documents where each value comes from and the choices made assembling them, so a user checking a specific GWP figure against a published table can trace it back to its source.

Sources

File	Contents	Source
`gwp_shortlist_epa.csv`	GWP values by gas, IPCC Assessment Report, and time horizon	EPA/data.gov IPCC AR4-AR6 GWPs (Federal LCA Commons), doi:10.23719/1529821; AR6 methane fossil/non-fossil split rows from the GHG Protocol’s Global Warming Potential Values (August 2024)
`gas_identity.csv`	Chemical formula and CAS Registry Number per gas	IPCC AR6 WGI Chapter 7 Supplementary Material, Table 7.SM.7 (via the chrisroadmap/ar6 CSV mirror); `gas_group` assigned manually
`gas_synonyms_seed.csv`	Documented alternate names per gas	GHG Protocol Global Warming Potential Values (August 2024) footnotes, IPCC AR6 Table 7.SM.7, and EPA/data.gov naming

gas_synonyms also includes each gas’s EPA/data.gov name, added automatically from gwp_shortlist_epa.csv’s epa_name column during the build (see data-raw/build_data.R).

AR6 values are taken from the final published tables

IPCC AR6 WGI Chapter 7 Supplementary Material, Table 7.SM.7, as hosted on ipcc.ch, contains incorrect values for CFC-11 and CFC-12. This is acknowledged by the chapter’s lead author for the metrics section (Bill Collins) via the chapter’s supplementary GitHub repository, but as of this writing no formal IPCC corrigendum has been issued. co2e uses the corrected values (sourced from the chapter author’s repository and independently corroborated by the GHG Protocol’s Global Warming Potential Values, August 2024) rather than the literal printed table for these two substances. This is the only known discrepancy between co2e and the printed Table 7.SM.7.

Scope

Single substances only. gases$is_blend is currently always FALSE
- refrigerant blends (e.g. R-410A) and ASHRAE R-number naming generally are not yet in scope. standardize_gas() will return "unmatched" for R-number names like "R-134a" until blend support is added.
Three time horizons. Only the 20-, 100-, and 500-year GWP horizons are included, matching what the source tables report.

Reproducing the built data

The tables shipped in data/ are built from the CSVs in data-raw/ by data-raw/build_data.R. Run it from the package root to regenerate them after editing a source CSV:

source("data-raw/build_data.R")