Executive Summary
Scope 3 emissions are widely recognised as the most significant component of an organisation's total emissions footprint. They represent indirect emissions that occur across an organisation's value chain, including suppliers, logistics, product use and downstream activity. For many organisations, Scope 3 can account for more than 70-90% of total emissions exposure. Despite this, Scope 3 remains one of the least understood and least consistently measured areas of climate reporting. The challenge is not simply one of measurement. It is structural. Scope 3 requires organisations to assess emissions across networks that are: external to the organisation, multi-tiered and interconnected, dominated by entities with limited disclosure, and dynamic and constantly evolving. As a result, organisations often rely on approximations, proxies and partial datasets, leading to outputs that are difficult to validate, compare or use in decision-making. This article explores what Scope 3 actually means in practice, why it is inherently difficult to measure at scale, and what a more effective approach looks like.
1. Context: Why Scope 3 Has Become Critical
Climate reporting has evolved rapidly from voluntary disclosure to structured, mandatory expectation. Frameworks such as AASB S2 and IFRS S2 now require organisations to: disclose emissions, explain exposure across value chains, and demonstrate how climate risk is managed.
Within this, Scope 3 plays a central role. It extends climate analysis beyond internal operations and into the broader ecosystem in which the organisation operates. This includes: upstream suppliers, transportation and logistics, product use and lifecycle, and downstream activities.
The implication is clear: Organisations are now expected to understand emissions not just within their control, but across the systems they depend on.
2. What Scope 3 Actually Represents
At a conceptual level, Scope 3 is straightforward. It captures indirect emissions that occur as a result of an organisation's activities.
In practice, however, it represents something more complex: A map of dependency across the value chain. Each supplier, partner or downstream activity represents a node within a broader network of emissions.
This network is large, fragmented, and often only partially visible. Unlike Scope 1 and 2, which can be measured internally, Scope 3 requires organisations to reach beyond their own boundaries.
3. The Structural Complexity of Scope 3
3.1 Multi-Tier Supply Chains: Most organisations have visibility over their direct suppliers (Tier 1). However, emissions often sit deeper in the chain: Tier 2 suppliers, Tier 3 suppliers, and raw material providers. Risk and emissions do not stop at the first tier. This creates a fundamental limitation: Organisations are being asked to measure emissions across entities they cannot fully see.
3.2 SME Dominance: A significant proportion of supply chain activity is delivered by SMEs. These entities often: do not publish emissions data, lack structured reporting frameworks, operate regionally or locally, and have limited digital footprint. This introduces a major data gap. While large suppliers may be visible, the broader network remains opaque.
3.3 Fragmented Data Sources: Relevant data sits across multiple systems: procurement platforms, supplier databases, logistics systems, and external ESG datasets. These systems are not designed to work together. They use different identifiers, formats, and update cycles. This makes integration difficult.
3.4 Dynamic Supply Chains: Supply chains are not static. They change due to: pricing pressures, availability of materials, project requirements, and supplier turnover. This means that Scope 3 exposure is constantly evolving. However, most analysis is periodic, static, and retrospective. This creates a mismatch between reality and measurement.
4. Why Traditional Approaches Fall Short
To address Scope 3, many organisations rely on: supplier questionnaires, spend-based models, industry averages, and consulting-led assessments. While these approaches provide a starting point, they have clear limitations.
4.1 Surveys and Questionnaires: These depend on supplier participation. Challenges include: low response rates, inconsistent data quality, and limited coverage.
4.2 Spend-Based Estimates: These apply emissions factors based on spend categories. While scalable, they are: highly approximate, not entity-specific, and difficult to validate.
4.3 Industry Averages: These assume that all entities within a sector behave similarly. In reality: businesses vary significantly, activities differ within sectors, and exposure is uneven.
4.4 Manual Analysis: Targeted reviews of key suppliers can be effective, but: do not scale, miss broader population risk, and require significant resource.
5. What This Means in Practice
The structural challenges of Scope 3 result in: incomplete coverage, reliance on proxies, inconsistent methodologies, difficulty comparing outputs over time, and limited auditability.
This affects both reporting quality and decision-making capability. Organisations may produce disclosures, but lack confidence in their accuracy or usefulness.
6. The Scale Problem
Scope 3 becomes exponentially more difficult as scale increases.
Assessing: 10 suppliers is manageable, 100 suppliers is challenging, and 10,000 suppliers becomes a structural problem.
At scale, organisations must: standardise data, ensure consistency, maintain coverage, and update analysis over time. This cannot be achieved through manual processes alone.
7. What Good Looks Like
A more effective approach to Scope 3 focuses on structure rather than estimation.
7.1 Entity-Level Mapping: Suppliers are mapped to consistent business entities. This enables: deduplication, standardisation, and consistent analysis.
7.2 Activity-Based Context: Emissions are linked to what businesses actually do, rather than static classifications.
7.3 Population-Level Coverage: Analysis extends across the full supplier base, not just selected entities.
7.4 Repeatability: Processes are designed to be updated regularly, applied consistently, and compared over time.
7.5 Integration: Scope 3 is connected to procurement, risk, and operations, rather than existing as a standalone exercise.
8. From Approximation to Analysis
The key shift is from estimating emissions to analysing exposure. This involves understanding: where emissions are likely to sit, how they are distributed across suppliers, and which segments are most material.
Closing Insight
Scope 3 is often approached as a calculation problem. In reality, it is a data and visibility problem across supply chains. Addressing it requires a structured way to connect suppliers, business activity, and emissions context across large populations of entities - enabling organisations to move from fragmented estimates to consistent, scalable analysis.