Skip to main content
Back to Glossary
Definition

GHG inventory uncertainty

GHG inventory uncertainty is the range or limitation around an emissions estimate caused by imperfect measurements, emission factors, assumptions, sampling, or calculation choices.

What is GHG inventory uncertainty?

GHG inventory uncertainty shows what may change an emissions estimate. GHG Protocol separates uncertainty in activity data and emission factors from uncertainty in the calculation model. It also separates random variation from systematic bias, a one-direction error such as a missing source or poorly matched factor.

Why does GHG inventory uncertainty matter to you?

Customers and verifiers may challenge an estimated total. For Australian entities within the reporting thresholds, AASB S2 Appendix D paragraphs 77-81 require the sources, assumptions and judgements behind highly uncertain amounts; sensitivity and possible outcomes may also need disclosure.

How does GHG inventory uncertainty work?

Start with the lines that could change the total most. Record the central result, the source of uncertainty, and the upper and lower bounds. State the confidence level, meaning how strongly the range is expected to contain the true value, and show whether it came from samples, a calibration certificate, or a documented judgement. Keep possible bias separate. Do not turn a missing source or country mismatch into an unsupported plus-or-minus percentage.

What mistakes should you avoid?

  • Giving a range without its confidence level or calculation basis.
  • Using a narrow measurement range as proof that the boundary and method are correct.
  • Combining ranges when the same assumption affects several inventory lines.

Does a wide uncertainty range mean the result is wrong?

No. Uncertainty describes a limit around an estimate; an error is something known to be incorrect. Correct known errors first, then label the remaining range and the data improvement that would narrow it.

What should you send when someone asks about uncertainty?

Send the affected line, result and unit, bounds, confidence level, calculation basis, activity record, factor key and version, assumptions, known bias, and the owner and date for the planned improvement.

Example

Suppose a steel fabricator in South Africa weighs an HFC-32 cylinder before and after charging a repaired air-conditioning unit. The service record shows a 6.0 kg difference after the unit was empty. A measurement procedure based on the scale's calibration certificate gives that difference an uncertainty of plus or minus 0.2 kg at 95% confidence, so the activity range is 5.8 to 6.2 kg.

Keslio factor key refrigerant_hfc_32_desnz_2026 is 677 kg CO2e/kg refrigerant. It is a non-geographic 100-year global warming potential factor from UK DESNZ and DEFRA's 2026 Government GHG Conversion Factors for Company Reporting. The central result is 6.0 kg x 677 kg CO2e/kg = 4,062 kg CO2e. The lower bound is 5.8 x 677 = 3,926.6 kg CO2e. The upper bound is 6.2 x 677 = 4,197.4 kg CO2e. Report this line as 4,062 kg CO2e plus or minus 135.4 kg, or 3.33%, at 95% confidence.

This range covers only the recorded refrigerant mass. It does not quantify scientific uncertainty in the global warming potential factor or a possible error in identifying the gas.

Where it comes up

GHG Protocol separation of statistical variation and systematic bias, calibration-based ranges, and uncertainty documentationShort Guidance for Calculating Measurement and Estimation Uncertainty, sections 2.2, 6.2 and 9Official sourceAASB S2 disclosure of highly uncertain amounts, sources, assumptions, sensitivity, and possible outcomesAASB S2 Appendix D, paragraphs 77-81

Related terms

GHG inventory

A GHG inventory is a dated record that fixes an organisation's boundary, lists its emissions sources and calculations, separates Scope 1, Scope 2 and Scope 3 totals, and documents methods, exclusions and supporting files.

Emission factor

An emission factor converts a measured activity, such as kilowatt-hours of electricity or litres of fuel, into greenhouse gas emissions by stating the emissions released per unit of that activity.

Primary vs secondary GHG data

Primary GHG data records a specific site, product, activity, or supplier, while secondary GHG data estimates that activity with external averages, databases, financial factors, or other proxies.

GHG accounting principles

GHG accounting principles require an inventory to be relevant, complete, consistent, transparent, and accurate so its boundary, methods, exclusions, and results can support decisions and withstand review.

Sustainability assurance

Sustainability assurance is an independent assessment of defined sustainability information against named criteria, ending in a report that states the provider's conclusion and level of assurance.

Sources

Last verified 2026-08-20

Ready to start?

Tell us what you need.

Bring us the sustainability request, reporting deadline, or strategy question you are facing. We will read it and suggest a practical first step, and the first conversation is free.

Get in touch
GHG inventory uncertainty Definition | Keslio