For the operational steps, see Calculate greenhouse gas emissions.

The aggregate extension is a GWP-weighted sum of matched gas accounts:

\[E_{\mathrm{GHG},j} = \sum_{g\in G}\mathrm{GWP}_g\,E_{g,j}.\]

The GWP factors come from the selected profile or explicit gwp mapping. The same weighted row sum is applied to final-demand emissions in EY. The aggregate rows are added to E and EY through add_extensions. Input gas rows must share one unit. An explicit unit must match that unit; this operation does not convert input magnitudes. Unmatched accounts are omitted; if no accounts match, the calculation raises KeyError.

Database.calc_ghg(
profile=None,
gwp=None,
label=None,
unit=None,
time_horizon=100,
ipcc_report='AR6',
inplace=True,
)#

Aggregate satellite GHG accounts into a new label row.

Profile (and its default GWP factors) is auto-detected from the parser metadata when profile=None. Pass gwp={...} to use custom factors. The aggregation is registered as a new satellite account in every scenario. Only stored environmental blocks are updated: on a native SUT these include Ea, Ec and EY. No economic matrices or unified SUT views are requested, and no scenarios are deleted.

Existing environmental coefficients, multipliers and footprints receive the same weighted row without further linear solves. Missing results remain available for on-demand calculation. Cached custom operators depending on updated environmental blocks are invalidated. Sparse storage, row labels and column axes are preserved; undefined values propagate for accounts with nonzero GWP factors.

Parameters:

  • profile – Registered profile name (see mario.ops.GHG_PROFILES). BONSAI is auto-detected and characterizes fossil CO2, fossil and non-fossil CH4, and N2O (Dinitrogen monoxide). Biogenic CO2 stays separate from the aggregate; NOx and resource CO2 uptake are not characterized. AR6/GWP100 also includes Accelerated CO2, Air with factor 0.00772, following BONSAI’s LCIA convention. That flow has no built-in factor for other reports or horizons; when present, those requests require an explicit gwp mapping. This profile covers the gases available in the Balanced bundle, which has no fluorinated GHG accounts.

  • gwp – Optional {satellite-account: factor} mapping that overrides the profile defaults.

  • label – Satellite-account label used for the aggregated row. When omitted, the label is derived from the GWP basis: built-in profiles yield "GHG {ipcc_report} GWP-{time_horizon}" (e.g. "GHG AR6 GWP-100"), while custom gwp=... mappings yield "GHG".

  • unit – Optional unit override. When omitted, the new row reuses the shared unit of the aggregated satellite accounts.

  • time_horizon – Time horizon used to resolve built-in profile GWPs when available. Default is 100. A factor must be available for each matched account at the requested horizon. Ignored when gwp=... is provided.

  • ipcc_report – IPCC assessment report used to resolve built-in profile GWPs when available. Supported built-in values currently are AR4, AR5, and AR6. Each matched account must have a factor for the selected report (BONSAI’s accelerated CO2 supports AR6 only). Ignored when gwp=... is provided.

  • inplace – When True mutate the database in place. When False return a modified copy.

Returns:

Modified database when inplace=False, otherwise None.

Return type:

Database | None

The new account is added to each existing scenario using that scenario’s environmental values. Economic blocks remain unchanged. In a native SUT, Ea, Ec and EY can be characterized directly without constructing the unified E, Z or z views.

Already materialized environmental coefficients, multipliers and footprints receive the weighted row directly; no missing matrices or linear systems are computed by this method. Custom operator caches depending on changed blocks are discarded for on-demand recalculation.

For BONSAI, db.calc_ghg() auto-detects the built-in profile. Its default AR6 GWP100 factors are 1 for fossil CO2, 29.8 for fossil methane, 27.0 for non-fossil methane, and 273 for N2O (Dinitrogen monoxide | Air), plus the BONSAI-specific factor 0.00772 for Accelerated CO2, Air | Air when that flow is present. The Nitrogen oxides (NOx) account is excluded. Non-fossil CO2 remains a separate account with factor zero in the aggregate, consistently with the existing EXIOBASE/GLORIA profiles. This convention does not calculate a net biogenic carbon balance or characterize resource CO2 uptake. The Balanced bundle has no fluorinated GHG accounts, so the profile covers its available greenhouse gases.

The conventional gas factors follow the GHG Protocol table of IPCC GWP values.

BONSAI characterization#

The built-in profile applies to both Balanced HSUT and native b2 HIOT inputs:

db.calc_ghg()  # Creates "GHG AR6 GWP-100", including Accelerated CO2.

The additional factor for Accelerated CO2, Air | Air follows the BONSAI LCIA.xlsx and its load_climate_factors / calculate_ghg_footprint routines checked locally on 21 October 2026. It is a BONSAI modelling convention, not a general IPCC factor for CO2. The source account remains available after characterization. No workbook is loaded automatically by MARIO.

Only the checked AR6/GWP100 factor is included for this flow. When it is present, requesting a different report or horizon without an available factor raises ValueError; provide an explicit gwp mapping for another characterization. When the flow is absent, the existing AR4/AR5 factors for the conventional gases remain available. Source UUIDs and readable labels can be matched through db.info["bonsai"]["satellites"].

The aggregate retains the input mass unit. HIOT multipliers f and HSUT commodity multipliers fc are expressed per native product unit. Comparisons with external results require the same source inputs and characterization.

Note

time_horizon and ipcc_report are used only when Database.calc_ghg(...) resolves a built-in profile. In the current built-in registry this affects gases such as CH4 and N2O; scalar entries such as CO2 and total GHG remain unchanged. When a custom flat gwp={...} mapping is passed, the method keeps the previous behavior and ignores these two arguments.