Explain a year-on-year emissions change before calling it progress

Fictional example: location-based purchased-electricity emissions only, in tCO2e. Recalculate Year 1, the assumed base year, first: 600 − 100 (divested site) − 20 (duplicate record) = 480. Then reconcile comparable periods in the stated activity-first order: 480 − 80 (electricity activity effect) − 50 (factor effect) = 350. Comparable electricity figures are 1,200 MWh × 0.40 tCO2e/MWh and 1,000 MWh × 0.35 tCO2e/MWh. The sold site existed in Year 1, and recalculation eligibility is assumed under a documented significance policy. The illustration does not establish causation or verified operational savings.

Before describing lower emissions as progress, reconcile the old reported figure to a comparable starting point, then explain the movement to the current year. A divestment, a corrected record, lower electricity consumption and a changing grid factor can all reduce a reported number. They support different conclusions.

This guide helps finance, operations and sustainability teams review an inventory movement. It provides an optional analytical method and a fictional example, not a prescribed GHG Protocol decomposition or a complete inventory.

Keep the comparison identifiable

Save the original reported total before making changes. Record the two reporting periods, entities and sites, consolidation approach, scopes, gases, units, calculation methods and factor versions. Identify the base year; it need not be the previous year.

Prepare separate movement records for:

• Boundary changes: transferred operations, dates and historical emissions.

• Method and data restatements: revisions and corrections, with reasons and affected years.

• Activity changes: changed quantities such as electricity consumed, fuel used or distance travelled, on a comparable basis.

• Factor changes: distinguish real changes from corrections or methodological updates.

Assign each effect once. Keep historical factor corrections out of current-year factor effects. Keep supporting calculations beside each entry rather than using an unexplained balancing figure.

Apply the recalculation policy before building the bridge

Apply a documented base-year policy consistently in both directions. Significant structural changes, method or accuracy improvements significantly affecting base-year figures, and significant errors, including cumulatively significant errors, trigger recalculation. Disclose its threshold; no universal percentage applies. Check programme rules. GHG Protocol recalculation FAQ

Organic growth or decline and real activity or factor changes do not trigger recalculation. Do not add an acquired operation to years before it existed. Assess outsourcing by scope. Corporate Standard, Chapter 5, pages 38–39

Keep an approved inventory restatement distinct from an exploratory management comparison. If an adjustment is still unresolved, label the analysis provisional and describe the missing evidence. Do not silently overwrite the published history or present an analytical subtotal as an approved recalculated base year.

First reconcile the original and comparable figures

All figures in this example are invented. The example covers only location-based purchased-electricity emissions, in tonnes of carbon dioxide equivalent (tCO2e). It is not a company's complete footprint. Year 1 is assumed to be the selected base year, with two complete twelve-month periods.

A fictional business originally reported 600 tCO2e in Year 1. It sold one site before Year 2 began; that site existed throughout Year 1 and contributed 100 tCO2e. Review also found a duplicate record worth 20 tCO2e at the continuing operations. Assume the documented policy and applicable requirements call for both historical recalculations, supported by adequate records.

• Original Year 1 report: 600 tCO2e.

• Remove the divested site's Year 1 emissions: −100 tCO2e.

• Remove the duplicate at continuing operations: −20 tCO2e.

• Recalculated, comparable Year 1: 600 − 100 − 20 = 480 tCO2e.

The 120-tonne adjustment changes the historical comparison. No operational saving has been demonstrated by those two entries. Retain both the original and revised records, with the adjustment decisions.

Then separate activity from the factor effect

For the continuing operations, assume comparable metering, geography, gas coverage and calculation methods. Year-specific factors are invented for arithmetic only and must not be used in real reporting:

• Year 1: 1,200 MWh × 0.40 tCO2e/MWh = 480 tCO2e.

• Year 2: 1,000 MWh × 0.35 tCO2e/MWh = 350 tCO2e.

Assume the factor decline represents a real change in the grid's emissions rate, not improved historical data or a changed methodology. Actual factor selection needs its own evidence; see Nitium's factor-selection guide.

Use an activity-first sequence: change consumption while holding the old factor fixed, then change the factor using current consumption.

1. Activity effect: (1,000 − 1,200) MWh × 0.40 tCO2e/MWh = −80 tCO2e.

2. Factor effect: 1,000 MWh × (0.35 − 0.40) tCO2e/MWh = −50 tCO2e.

The comparable movement is −80 − 50 = −130 tCO2e. The complete bridge reconciles: 600 − 100 − 20 − 80 − 50 = 350 tCO2e. The residual, current emissions minus the reconciled result, is zero.

For several sources, calculate each comparable source separately before adding effects. Missing records, mixed units or a changing source mix can be hidden by an aggregate average factor. Show unresolved differences openly; a zero residual establishes arithmetic closure, not evidence quality.

Show why the calculation order matters

Changing the factor first gives 1,200 × (0.35 − 0.40) = −60 tCO2e, followed by (1,000 − 1,200) × 0.35 = −70 tCO2e for activity. The total remains −130, but the allocation differs.

The interaction is (−200 MWh) × (−0.05 tCO2e/MWh) = +10 tCO2e. Activity-first places it in the factor effect; factor-first places it in the activity effect. State the sequence and use it consistently. Do not include the interaction again after it has already been allocated, or present either allocation as a uniquely measured causal contribution.

Write the conclusion using the right comparison

Compared with the original 600 tCO2e, the reported figure falls by 41.7%. Against the recalculated 480 tCO2e, it falls by 27.1%. Both percentages use unrounded calculations and are displayed to one decimal place. They answer different questions; name the denominator whenever stating the change.

If matched output at the continuing operations is an invented 300 tonnes in Year 1 and 250 tonnes in Year 2, emissions intensity falls from 1.6 to 1.4 tCO2e per tonne, or 12.5%. Electricity per tonne remains 4 MWh in both years. Keep absolute emissions, output and intensity visible; the matched-intensity guide covers constructing that ratio.

A suitable conclusion for this example is: “Location-based electricity emissions fell by 130 tCO2e against recalculated Year 1. In the stated activity-first analysis, lower consumption contributes 80 tonnes and the lower grid factor 50 tonnes. The separate 120-tonne historical adjustment comprises the divestment and correction.”

The Scope 2 Guidance notes that a lower grid factor can reduce reported emissions without a specific corporate action. Scope 2 Guidance, section 9.3 Investigate output, operating hours, weather and interventions before calling the consumption effect an efficiency saving. See Separate energy savings from changes in production. Where dual reporting applies, prepare distinct comparisons for each method; keep location-based and market-based results separate.

Keep the evidence and edition with the explanation

Retain the bridge, supporting records, approvals, decomposition order and open questions. Have a second reviewer reproduce the bridge and challenge the proposed claim. Nitium's related Emissions movement explanation workbook is listed separately in the resource directory.

This guide uses the Corporate Standard Revised Edition (2004) and Scope 2 Guidance (2015). As checked on 13 October 2026, their consolidated replacement remains under development. GHG Protocol's September 2026 update anticipates consultation in Q2 2027 and publication in Q4 2028; proposals are not final requirements. Official development update

Nitium's carbon inventory support covers inventory preparation, calculation workbooks and source-and-assumptions records within an agreed scope. Discuss your inventory needs with a non-confidential description of the movement you need to explain.

Sources checked 13 October 2026. The example is fictional and simplified. This guide does not provide independent assurance, certify compliance or establish a project's emissions reduction.