Climate Reporting Standards: ISSB, GRI, and Mandatory Disclosure
What Are the Key Climate Reporting Standards and What Do They Require?
Corporate climate disclosure has shifted from voluntary best practice to mandated compliance with measurable and auditable requirements. The proliferation of reporting frameworks — GRI, TCFD, CDP, CDSB, SASB — that characterized the 2010s is giving way to convergence around a smaller number of authoritative standards. The ISSB's IFRS S2 represents the most significant step toward a global baseline; CSRD's ESRS E1 creates the most detailed requirements in any jurisdiction; and the SEC's climate disclosure rule extends mandatory requirements to US-listed companies. Understanding these standards is essential for investors who rely on disclosed data and for companies that must comply.
Climate reporting standards are codified frameworks specifying what climate-related information companies must disclose, in what form, with what level of assurance, and when — enabling investors to make comparable assessments of climate risk and opportunity across companies.
Key Takeaways
- IFRS S2 (ISSB) provides a global baseline aligned with TCFD, requiring governance, strategy, risk management, and metrics/targets disclosures.
- CSRD's ESRS E1 is the most detailed mandatory standard, covering double materiality, full Scope 1/2/3 emissions, physical risk, and transition planning.
- The SEC climate disclosure rule (finalized 2024, subsequently stayed pending litigation) would require Scope 1 and 2 disclosures from US-listed companies, with Scope 3 requirements removed.
- GRI 305 remains the most widely used emissions disclosure standard globally by number of reporting companies.
- Convergence between ISSB and CSRD is ongoing; EU sustainability reports using ESRS can achieve "equivalent" status with IFRS S2, reducing dual-reporting burden.
The Pre-2020 Landscape: Fragmentation and Voluntary Disclosure
Before 2020, corporate climate disclosure was characterized by:
- CDP: Voluntary questionnaire collecting detailed emissions, energy, and risk data from thousands of companies annually
- GRI Standards: Widely adopted framework; GRI 305 covers atmospheric emissions
- TCFD: Four-pillar framework (Governance, Strategy, Risk Management, Metrics and Targets) recommended in 2017; adopted voluntarily by thousands of companies and mandated in some jurisdictions
- SASB: Sector-specific standards for financially material sustainability topics
- CDSB: Climate Disclosure Standards Board framework aligned with financial reporting
This fragmentation created inconsistency, incomparability, and high reporting burden. The IFRS Foundation's 2020 consultation on a Sustainability Standards Board led to the formation of the ISSB in 2021, consolidating TCFD, SASB, CDSB, and other frameworks into a single body.
IFRS S2: The Global Baseline
Overview
IFRS S2 Climate-related Disclosures was published by the International Sustainability Standards Board (ISSB) in June 2023, effective for annual reporting periods beginning on or after January 1, 2024. It is designed as a global baseline — jurisdictions can build upon it with additional requirements but should not reduce its core disclosures.
IFRS S2 is modeled directly on TCFD, incorporating and superseding the TCFD recommendations. The four disclosure pillars are:
Governance — Board and management-level processes for overseeing climate-related risks and opportunities. Requires description of board committees responsible for climate oversight, management positions with climate accountability, and incentive structures linked to climate targets.
Strategy — Climate-related risks and opportunities over short, medium, and long-term; their effects on business model and strategy; resilience of strategy under climate scenarios. Requires scenario analysis disclosure, including the scenarios used and key assumptions.
Risk Management — Processes for identifying, assessing, and managing climate-related risks; how these processes integrate into overall enterprise risk management.
Metrics and Targets — Scope 1, 2, and 3 GHG emissions, cross-industry metric categories (climate-related transition risks/opportunities, physical risks/opportunities, climate-related targets, carbon offsets), and industry-specific metrics from SASB standards.
Scope 3 under IFRS S2
ISSB S2 requires Scope 3 disclosure if deemed material, with a one-year phase-in provision allowing companies to begin Scope 3 reporting one year after Scope 1 and 2. The materiality assessment for Scope 3 follows IFRS financial materiality (single materiality: investor perspective), not double materiality. This distinguishes ISSB from the EU approach.
Adoption
By mid-2024, ISSB standards had been adopted or committed to by over 30 jurisdictions including Australia, Canada, Hong Kong, Japan, Malaysia, New Zealand, Singapore, and the UK. IOSCO endorsed the ISSB standards in 2023, creating a pathway for adoption across securities regulators globally.
CSRD and ESRS E1: The European Standard
The CSRD Framework
The Corporate Sustainability Reporting Directive (CSRD), which entered into force in January 2023, requires EU-based large companies and non-EU companies with significant EU presence to report under European Sustainability Reporting Standards (ESRS). The ESRS were adopted by the European Commission as delegated regulations. Mandatory climate reporting falls under ESRS E1 (Climate Change).
CSRD applies to:
- Large EU public-interest entities: reporting from 2024 (FY 2023)
- Other large EU companies: reporting from 2025 (FY 2024)
- Listed SMEs: reporting from 2027 (FY 2026, with opt-out to 2028)
- Non-EU companies with >€150M EU net turnover and at least one EU subsidiary or branch: from 2028 (FY 2028)
ESRS E1 Requirements
ESRS E1 is the most detailed mandatory climate standard globally. Key disclosure requirements include:
Transition plan — A description of the company's transition plan for climate change mitigation, including targets, milestones, and capital expenditure plans.
Physical and transition risk assessment — Detailed assessment of acute and chronic physical risks and policy/technology/market transition risks using scenario analysis, with explicit geographic asset-level exposure where material.
Gross Scope 1, 2, and 3 emissions — All three scopes required without phase-in or materiality escape hatch for large companies. Scope 3 must cover all 15 categories where material.
GHG removal and carbon credits — Separate disclosure of GHG removals, carbon credits used for net calculation, and the quality of those credits.
GHG intensity metrics — Revenue-normalized GHG intensity disclosed alongside absolute emissions.
Double materiality — ESRS E1 requires both impact materiality (the company's effects on climate) and financial materiality (climate's effects on the company), integrating both perspectives into risk and opportunity assessment.
Limited assurance — Initially required for all sustainability data; pathway to reasonable assurance by 2028.
The SEC Climate Disclosure Rule
History
The US Securities and Exchange Commission proposed comprehensive climate disclosure rules in March 2022, covering Scope 1, 2, and 3 emissions for US-listed companies. After receiving thousands of public comments, the SEC adopted a final rule in March 2024. Before implementation, the rule was stayed by federal courts pending challenges from business groups arguing the rule exceeded SEC authority.
What the Final Rule Required (Before Stay)
The March 2024 final rule, compared to the initial proposal, was significantly reduced in scope:
- Scope 1 and 2: Required for large accelerated filers and accelerated filers if material; required with reasonable assurance for large accelerated filers after transition periods.
- Scope 3: Removed entirely from the final rule (a major retreat from the proposal).
- Financial statement footnote: Climate-related financial impacts above a materiality threshold must be disclosed in financial statement footnotes with standard financial auditing requirements.
- Scenario analysis and transition plans: Not required; only required to disclose whether the company uses scenario analysis, not the results.
Status
The rule's legal status remained uncertain as of mid-2024, with multiple circuit courts potentially hearing challenges. California's SB 253 (Climate Corporate Data Accountability Act, enacted 2023) independently requires Scope 1, 2, and 3 disclosure from companies with >$1 billion revenue doing business in California, effective from 2026, potentially covering thousands of US companies regardless of federal SEC rule status.
GRI 305: The Most Widely Used Standard
GRI 305 (Emissions) within the GRI Universal Standards covers Scope 1, 2 (both location-based and market-based), and Scope 3 GHG emissions; other significant air emissions (NOx, SOx, particulate matter); and biogenic CO₂. GRI 305 is used by thousands of companies globally as the basis for sustainability report emissions sections.
GRI revised its standards in 2021 with GRI 305-1, 305-2, 305-3 aligning more closely with GHG Protocol methodology. CSRD explicitly states that companies complying with ESRS E1 should satisfy the corresponding GRI 305 requirements.
Convergence and Interoperability
A key development since 2022 has been formal collaboration between ISSB and GRI on an interoperability mapping, allowing companies that report under both to avoid duplicating effort. EFRAG (European Financial Reporting Advisory Group), which develops ESRS, has published an interoperability index with ISSB S1/S2, showing how ESRS reporters can simultaneously achieve ISSB-aligned disclosure.
This convergence reduces the concern that global companies would face incompatible requirements from different jurisdictions — though full harmonization remains a long-term aspiration rather than a current reality.
What Investors Should Look For
Completeness of Scope 3 disclosure — Companies reporting all 15 Scope 3 categories with methodology explanations provide fundamentally different analytical utility than those reporting one or two categories.
Third-party assurance scope — Reasonable assurance provides stronger reliability signals than limited assurance; limited assurance is better than no assurance. The scope of assurance (which emissions categories, which boundaries) matters as much as the assurance type.
Scenario analysis quality — Generic "we used 2°C scenarios" disclosures are less useful than detailed scenario narratives including the IEA/NGFS scenarios used, key assumptions, and how results inform strategy.
Target robustness — SBTi-validated targets with interim milestones and Scope 3 coverage are more credible than internal targets without external validation.
Common Mistakes
Assuming ISSB adoption means ESRS-level disclosure. ISSB S2 is a baseline; ESRS E1 is significantly more demanding in Scope 3 requirements, double materiality, and transition plan detail. Companies meeting ESRS E1 exceed ISSB; companies meeting only ISSB minimum may fall short of what EU investors expect.
Treating the SEC rule as settled. The legal uncertainty around the US federal rule means US companies' disclosure obligations may be determined by state law (California) or investor pressure rather than federal securities regulation.
Overlooking base year restatements. ISSB and ESRS both allow or require base year restatements when significant changes occur (acquisitions, divestitures, methodology changes). Time-series analysis must account for restated base years to avoid misleading trend analysis.
Frequently Asked Questions
Is TCFD now obsolete? TCFD was formally disbanded in October 2023 after recommending that ISSB take over monitoring of corporate climate disclosure progress. TCFD recommendations are incorporated in IFRS S2, so companies reporting under S2 satisfy TCFD simultaneously. TCFD as a standalone recommendation is no longer being updated, but its four pillars remain the structural backbone of climate reporting globally.
What is double materiality? Double materiality requires companies to assess both (1) how climate change affects the company (financial materiality, investor perspective) and (2) how the company affects climate (impact materiality, stakeholder perspective). ESRS E1 requires both; ISSB S2 requires only financial materiality. This distinction significantly affects the scope of required disclosure, particularly for Scope 3 emissions.
When must EU companies comply with ESRS E1? Large EU public-interest entities (listed companies, banks, insurers with >500 employees) must report under ESRS for fiscal year 2024, with reports published in 2025. Other large EU companies begin for FY2025. Listed SMEs can delay to 2027 with an opt-out to 2028.
Related Concepts
Summary
The climate reporting landscape is converging toward two main poles: IFRS S2 as the global baseline for financial markets, and CSRD/ESRS E1 as the more detailed EU mandatory standard incorporating double materiality. The SEC climate rule's legal status adds uncertainty for US-listed companies, while California's SB 253 independently extends Scope 3 requirements to large companies doing business in the state. For investors, the most important development is the shift from voluntary to mandatory disclosure with assurance requirements — significantly improving data quality and comparability for climate financial analysis.