Carbon baseline

A carbon baseline is the footprint you compare everything else against. You pick a base year, measure your emissions for that period in tonnes of CO2e, and from then on every target and every claim of progress is measured from that number. “We will cut emissions by 50% by 2035” only means something once you know what the 100% was.

What it means for a small business

You need a baseline as soon as anyone asks you to show change over time. That includes:

• Carbon targets, such as net zero or a percentage cut, which are always set against a base year
• Grant applications, where funders want to see your starting point and the savings a project will deliver
• Carbon Reduction Plans for central government tenders under PPN 006, which ask for baseline emissions
• The SME Climate Hub commitment, which asks you to halve emissions and report progress each year
• Science-based targets, which are set from a defined base year

Choose a recent 12-month period you have good data for, such as your last financial year. A year distorted by something unusual, like a long office closure, makes a poor baseline.

The GHG Protocol also expects you to recalculate your baseline when your business changes significantly. Typical triggers are buying or selling part of the business, bringing an outsourced activity in-house, changing your calculation method, or finding a significant error. You set your own threshold for “significant” and apply it consistently. Normal growth, such as hiring more staff, is not a reason to recalculate. That growth is part of the progress you are measuring.

An example

A 10-person architecture practice measures 14.2 tCO2e for the year to 31 March 2026 and sets that as its baseline. It commits to halving emissions within ten years. In 2028 it merges with a smaller studio that brings its own office and two company cars. Because that is a structural change, the practice adds the studio’s base-year emissions to its baseline, so its progress figures still compare like with like.

How ESG Now handles it

Your ESG Now report gives you a baseline by scope and source, calculated with the UK Government conversion factors matched to your reporting period, with every line of working shown. The targets section records your baseline year, target year and any previous footprint. For grant forms, see our guide to a carbon baseline for grant applications, or start your free report.