Most Scope 3 numbers are secondary data, and the disclosure should say so

Companies reporting to CDP disclosed Scope 3 supply chain emissions that were on average 26 times their operational emissions. Only 15 percent had set a Scope 3 target.¹

The GHG Protocol Scope 3 Standard groups those emissions into 15 categories and allows spend-based and average-data methods where supplier data is unavailable.² That is legitimate. Presenting the result as if it were measured is the problem.

What to disclose

The standard's five data quality indicators are technological, temporal and geographical representativeness, completeness and reliability. Its scoring example rates temporal representativeness as very good for data less than three years old and poor for data more than ten years old or of unknown age.³ Score each category against those indicators and publish the share calculated from supplier-specific data.

Then go after primary data where it moves the total. That is usually the largest suppliers by emissions, which are not always the largest by spend.

After Omnibus I

Directive (EU) 2026/470 narrowed the CSRD to companies with more than 1,000 employees and more than €450 million net turnover, for financial years starting on or after 1 January 2027.⁴ Fewer companies will report under ESRS, but those that do still need their suppliers' data, so requests continue down the value chain through large customers. The GHG Protocol is also revising the Scope 3 Standard; its March 2026 progress update says a full draft for public consultation is still to come.⁵