Scope 1–3 emissions model

The previous year's figure had been built in a spreadsheet nobody could fully explain. Assurance raised evidence requests the team could not answer quickly, and each one cost days.

Scope 3 was the hardest part: spend-based estimates mixed with supplier-reported actuals, with no consistent record of which method had been used where.

Each emissions source became a modelled table carrying its activity data, emission factor, factor source and calculation method as columns — so the method is part of the record, not a footnote.

Factor versions are pinned by reporting year, which means a restatement is explicit rather than a silent change when a factor library updates.

The assurance pack became a query. Evidence requests that previously meant reconstructing a calculation now resolve by pointing at the row and its lineage.