Baseline year

“A baseline is a fixed point for comparison, not a permission to forget what changed around it. ”

A climate target usually promises a percentage reduction from a baseline year. The choice establishes the inventory against which progress will be judged. It seems administrative, but it can materially affect ambition and interpretation. Organisations often choose a recent year with reliable data.

Some choose a year before an unusual disruption; others choose a year with high emissions that makes subsequent reductions appear larger. Standards generally require the year to be representative and the inventory complete enough to support consistent tracking. The baseline must also survive organisational change. Acquisitions, divestments, outsourcing and methodological improvements can alter the boundary.

Without recalculation rules, a company may claim reductions created by selling assets or correcting data rather than changing emissions.

Structural changes above a significance threshold should trigger restatement of the baseline. Exceptional years require judgement. Pandemic closures, strikes, extreme weather or one-off production changes may make a year unrepresentative. Selecting another year can be legitimate, but the rationale should be transparent and applied before results are known.

Base years can create perverse incentives when they become political artefacts. A target anchored in an old high-emissions year may look ambitious while requiring little new action. The more useful test is the annual trajectory from current performance to the required end state. For practitioners, baseline governance matters as much as baseline selection.

The inventory should be reproducible, changes documented and restatements visible so users can distinguish real-world reduction from accounting movement.

Practical application

Publish the baseline year, boundary, scopes, data completeness and rationale. Define a recalculation policy for structural changes, methodology updates and significant errors. Preserve both originally reported and restated series.

Why it matters

Target credibility depends on a stable, representative reference. Weak baseline governance can manufacture progress or make performance incomparable.

Common misconception

Once selected, a baseline must never change. It should be recalculated when defined structural or methodological changes would otherwise distort comparison.

Connections

Science-Based Targets use baseline years. Restatement preserves comparability. Absolute Target and Carbon Intensity determine how progress is expressed.

A question worth asking

Would your claimed reduction remain after adjusting the baseline for acquisitions, divestments and improved data?

Selected references

GHG Protocol, Corporate Standard, base-year recalculation guidance. Science Based Targets initiative, target validation criteria and FAQs. ISO 14064-1, organisation-level greenhouse-gas inventories.