SB 253 Scope 3 supplier data: start with a focused pilot to improve emissions data quality
California Climate Disclosure — Scope 3 Supplier Data
Scope 3 preparation is not a mass-email exercise. The fastest route to better data is to identify the categories and suppliers that materially influence the inventory, request only information that will be used, and create a repeatable review process.
Why act early
CARB describes SB 253 as covering Scope 1, Scope 2 and Scope 3 emissions, with the statutory program phased across reporting cycles. Detailed 2027-and-beyond methods and timing should be checked against the latest CARB rulemaking before publication or implementation.
Begin with the inventory, not the questionnaire
Use the current spend-based or activity-based estimate to identify likely hotspots. Segment suppliers by emissions relevance, spend, strategic importance, data maturity and ease of engagement. A small pilot with representative suppliers can expose process failures before the request expands.
A practical supplier-data hierarchy
- Level 1 — Supplier-specific, product- or activity-level primary data: Preferred where material, credible and supported by methodology
- Level 2 — Supplier corporate emissions allocated using a documented basis: Useful when product-level data is unavailable
- Level 3 — Physical activity data with recognized emission factors: Stronger than spend where quantities and specifications exist
- Level 4 — Spend or industry-average estimates: Useful for screening and gaps, with limitations recorded
What to request from suppliers
- Reporting period and organizational or product boundary.
- Emissions value, unit and greenhouse gases included.
- Calculation methodology and emission-factor sources.
- Allocation method, if the result is assigned to a product or customer.
- Verification or assurance status.
- Primary versus estimated data share and known exclusions.
- Named contact and permission to use the information for reporting.
Build quality checks into intake
Validate units, periods, boundaries and duplicates before loading data. Flag unexplained year-on-year changes, unsupported zero values, incompatible product units and totals that cannot be reconciled. Store the original supplier response alongside any transformed value used in the inventory.
A 90-day pilot
- Days 1–20: prioritize. Confirm material Scope 3 categories, select a manageable supplier cohort and agree success measures with procurement and sustainability teams.
- Days 21–45: request. Send a short, role-specific request with definitions, acceptable formats, support contacts and a realistic deadline. Explain why the data is needed and how it will be used.
- Days 46–70: validate. Review completeness and methodology. Resolve the highest-impact gaps first; do not spend equal effort on immaterial suppliers.
- Days 71–90: learn and scale. Measure response rate, usable-data rate, time per review and emissions coverage. Refine the request and integration process before adding more suppliers.
How smaller suppliers are affected
A supplier may be below California’s direct revenue thresholds and still receive data requests from covered customers. Buyers can improve response quality by avoiding legalistic questionnaires, accepting staged improvements and providing a clear route for questions.
Success measures
- Percentage of estimated category emissions covered by the pilot.
- Supplier response rate and usable-data rate.
- Share of primary versus secondary data.
- Average review time and number of clarification cycles.
- Number of material methodology issues resolved.
Design your supplier-data pilot
Design a GreenKPO supplier-data pilot that focuses procurement effort on the suppliers and categories that can materially improve the Scope 3 inventory.