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Scope 3 Reporting Reliability and Assurance Gaps in FTSE 100 Transition Plans

Value chain greenhouse gas accounting forms the foundational pillar of contemporary corporate decarbonisation strategies yet exhibits structural vulnerabilities in measurement reliability and third-party verification. Disparities in boundary delimitation, indirect estimation models, and superficial assurance scopes systematically weaken the evidentiary integrity of public transition plans across capital markets. Evaluating these systemic accounting and auditing deficits enables the formulation of rigorous governance criteria to enhance the transparency and institutional credibility of corporate net-zero commitments.

Goal of work

How do Scope 3 calculation discrepancies and external assurance limitations affect the credibility of climate transition plans among FTSE 100 companies?

Methodology

Comparative secondary analysis of corporate transition disclosures, non-financial assurance reports, and regulatory frameworks using Critical Systems Thinking.

Scientific novelty

Synthesises Critical Systems Thinking with climate assurance analysis to expose structural carve-outs and estimation vulnerabilities in corporate transition governance.

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PhD Thesis

Degree:
Scope 3 Reporting Reliability and Assurance Gaps in FTSE 100 Transition Plans

Author:

Group

First M. Last

Advisor:

Dr. First Last

City, 2026

Contents

Declaration of Originality
Abstract
Introduction
Chapter 1. Conceptual Framework of Value Chain Emissions and Assurance
1.1 GHG Protocol and Scope 3 Boundary Delimitation
1.2 Institutional and Stakeholder Pressures on Corporate Transition Disclosures
1.3 Epistemic Gaps and Methodological Pluralism in Upstream and Downstream Accounting
1.4 Critical Systems Perspectives on Value Chain Boundary Ambiguity
Chapter 2. Regulatory Architecture and Corporate Transition Governance
2.1 UK Transition Plan Taskforce Framework and Listing Rules
2.2 Comparative Alignment with ISSB and European Reporting Directives
2.3 Corporate Governance Mechanisms and Sustainability Committee Oversight
2.4 Statutory Ambiguities and the Persistence of Voluntary Reporting Regimes
Chapter 3. Methodological Framework for Transition Plan and Assurance Assessment
3.1 Research Philosophy and Multi-Tier Document Analysis Protocol
3.2 Corpus Selection and Longitudinal Categorisation Criteria
3.3 Qualitative Verification Metrics for Value Chain Disclosures
3.4 Reliability, Methodological Limitations, and Epistemic Risk Management
Chapter 4. Evaluation of Scope 3 Disclosure Reliability across the FTSE 100
4.1 Heterogeneity in Scope 3 Calculation Models and Estimation Proxies
4.2 Double Counting and Boundary Allocation Vulnerabilities
4.3 Strategic Decoupling between Net-Zero Pledges and Physical Value Chain Decarbonisation
4.4 Cross-Sectoral Disparities in Upstream Supplier Engagement and Data Maturity
Chapter 5. Critical Analysis of Third-Party Assurance Gaps and Audit Practice
5.1 Limited versus Reasonable Assurance Standards in Non-Financial Disclosures
5.2 Scope Carve-Outs and Caveats in External Audit Engagements
5.3 Emerging Technological Interventions and Systems-Based Verification Models
5.4 Institutional Impediments to Comprehensive Value Chain Verification
Chapter 6. Strategic and Policy Implications for Transition Integrity
6.1 Standardisation Pathways for Robust Value Chain Attribution
6.2 Enhancing Audit Accountability and Governance Protocols for Corporate Boards
6.3 Recommendations for Financial Regulators and Standard-Setting Bodies
Appendix
Conclusion
Bibliography

Introduction

Corporate decarbonisation pledges within the United Kingdom increasingly hinge upon the credibility of long-term climate transition plans published by large public corporations. Within the FTSE 100 index, voluntary and quasi-mandatory disclosures have expanded rapidly to satisfy capital market demands for transparent environmental, social, and governance reporting [1]. However, indirect value chain emissions classified under Scope 3 constitute the overwhelming majority of aggregate corporate footprints, while simultaneously presenting acute structural vulnerabilities in data integrity, boundary delimitation, and longitudinal reliability across industrial sectors [3].

The fundamental challenge in evaluating corporate transition integrity lies in the profound divergence between public net-zero commitments and the verification mechanisms governing indirect emissions. Highly fragmented supply chains, reliance on unstandardised secondary proxies, and systemic estimation biases frequently obscure the boundary between genuine operational abatement and symbolic reporting compliance [5]. Concurrently, third-party assurance protocols remain predominantly confined to limited assurance levels or routinely exclude complex Scope 3 categories from formal audit scopes, thereby exacerbating information asymmetries between disclosing boards and external institutional investors [6].

This inquiry addresses these systemic disclosure deficiencies by investigating how Scope 3 reporting inaccuracies and external verification deficits interact across FTSE 100 transition frameworks. By synthesizing critical systems perspectives with comparative regulatory analysis and non-financial audit scholarship, the research conceptualises how market-driven transition planning negotiates systemic data fragmentation and evolving statutory mandates [2], [3]. The resulting analytical framework establishes rigorous criteria to diagnose structural assurance boundaries, evaluate value chain accountability, and strengthen institutional oversight of corporate net-zero commitments.

3.1 Research Philosophy and Multi-Tier Document Analysis Protocol

Developing a robust methodological approach to evaluate non-financial reporting requires addressing the profound fragmentation inherent in value chain greenhouse gas disclosures. In assessing corporate climate transition plans, traditional documentary analysis encounters systemic challenges stemming from the opaque, distributed, and unstandardised nature of upstream and downstream data streams. Rather than relying on simple linear compliance frameworks, a Critical Systems Thinking perspective provides a structured lens to examine the underlying assumptions, boundary definitions, and power asymmetries that govern reporting practices across complex corporate value chains [6]. The comparative evaluation framework focuses on secondary documentary evidence, encompassing published corporate transition strategies, non-financial disclosure statements, and external assurance statements issued by professional service providers. By applying qualitative assessment criteria to these documentary corpora, the research examines the depth and scope of external verification, contrasting broad narrative disclosures with specific audit limitations and carve-outs. This systematic categorization distinguishes between limited assurance engagements—which provide only negative assurance regarding material misstatements—and comprehensive validation of technical estimation proxies [3]. Consequently, the secondary analytical architecture evaluates whether the chosen measurement boundaries and accounting methodologies provide an auditable basis for corporate climate alignment, identifying the structural junctures where assurance deficits undermine overall disclosure credibility.

References

  1. Sustainability Reporting Practices in FTSE 100 Companies
    Nuha Ceesay, Moade Shubita, Fiona Robertson
    DOI Link
  2. “Transition Plans Are Dead, Long Live Transition Plans?”: The Rise, Fall and Persistence of Climate Transition Plans in the EU
    Federica Agostini, Nicolo' Galasso
    DOI Link
  3. Navigating Climate Risks: Reporting Practices and Assurance for a Sustainable Future
    Fasilat Aramide Sanusi, Muhammad Nurul Houqe, Dimu Ehalaiye
    DOI Link
  4. The Reporting of Greenhouse Gas Emissions: Market-based Scope 2 Emissions and Renewable Energy Instruments
    Mary Brooke Billings, Svenja Dube, Han Yan
  5. Scope 3 emissions reporting and virtue signaling
    Neil McNaughton
  6. Conceptualization of Artificial Intelligence Use for GHG Scope 3 Emissions Measurement, Reporting, Monitoring, and Assurance: A Critical Systems Perspective
    Tehmina Khan, David Teh
  7. Quality Assurance Project Plan for radioactive airborne emissions data compilation and reporting
    S.A. Burris, S.P. Thomas
  8. A Systematic Review of Public Sector Climate-Risk Reporting and Assurance Practices: A Conceptual Framework Towards Responsible Governance in Sub-Saharan Africa
    Joseph Tinarwo, Lourens Erasmus

Bibliography

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