Why your Scope 3 number will move, and why that is fine

Almost every company that takes Scope 3 seriously has the same uncomfortable moment. After a year of supplier engagement and better data, the footprint goes up. Sometimes by a lot.

This is not failure. It is what happens when estimates are replaced by evidence.

Why the number moves

• Method changes. Moving from spend-based factors to supplier-specific data can change a category's emissions in either direction.
• New categories. First inventories often skip categories that seemed small, such as use of sold products or investments, and these can turn out to be large.
• Better factors. Emission factor databases are updated, and industry averages are replaced with more specific ones.
• Boundary corrections. Acquisitions, divestments and clearer organisational boundaries change what is counted.

What good practice looks like

The GHG Protocol expects companies to set a recalculation policy: a threshold (often around 5%) above which the base year is restated when methods, data or boundaries change significantly. Applied consistently, this keeps the trend comparable, even when the absolute number moves.

1. Disclose the method by category. Readers need to know which numbers are spend-based and which are primary data.
2. Separate real change from method change. Show how much of the movement came from operations and how much from better data.
3. Restate the base year when your policy says so. Do it openly, with an explanation.
4. Track data quality as a metric. The share of Scope 3 based on supplier-specific data is itself a sign of progress.

The credibility test

Investors and assurance providers are not alarmed by restatements. They are alarmed by numbers that never change, by methods that are not explained, and by targets that are met only because of an accounting choice. A company that says "our footprint rose 12% because we replaced estimates with supplier data, and here is the like-for-like trend" is more credible than one that reports a smooth decline nobody can check.

Educational content, not legal advice.