Which numbers, from where?

The factor choice is part of the result

Two firms can report very different numbers for the same product and both be defensible, because source, geography, year, system boundary and calorific basis all move the answer.

That is why the choice is recorded rather than merely applied: every calculation stores which factor, at which version, from which source produced the figure. A question about methodology has a stored answer.

A versioned, checksummed catalogue

Core factors live in a versioned catalogue with recorded provenance and checksums, so a factor update is a deliberate, dated event rather than a silent change — and past reports remain reproducible against the version they used.

Where the uncertainty concentrates

Not every figure in an inventory is equally solid, and rather than hide that we measure it. The tightest end is Scope 1 and 2 resting on signed meter readings: there the uncertainty is that of the instrument and the grid factor. The widest end is Scope 3 lines estimated from spend: a factor that converts money into emissions is a sector average, and it does not know your supplier.

That is why a calculation returns a number plus an error band, and the band comes from the method itself. When measured supplier data arrives the band narrows and where it came from goes on the record — the moment an estimate is replaced by a measurement becomes visible. Even where supplier data is anchored, its own uncertainty is carried through: an anchor does not make a number certain.

We also record separately where the data came from — a signed instrument reading, a source document, or a declaration. This is an axis SEPARATE from "who verified it": a figure that has passed independent assurance may rest entirely on hand-entered data.

Evidence provenance: same number, three levels of reliability →

You do not have to take any of this on trust

The only meaningful test of everything above is this: can you take a figure and recompute it yourself? That is what the verifier is for — it recomputes the hashes and the Merkle path in your own browser. No account, no API key, no need to trust us.

Verify a record →