New Regulatory Era for Corporate Climate Disclosures

California has become the first U.S. state to mandate comprehensive corporate greenhouse gas (GHG) disclosures and climate-related financial risk reporting across a broad swath of the private sector. The California Climate Accountability Package, anchored by Senate Bills 253 and 261 and supported by SB 219, lays the foundation for a climate transparency regime that will affect thousands of large businesses operating in the world’s fifth-largest economy [1][2][3].

This landmark legislative initiative arrives amid growing pressure from regulators, investors, and civil society for companies to disclose and manage climate-related risks. Modeled in part on global frameworks such as the 気候関連財務情報開示タスクフォース（TCFD） そして GHGプロトコル, California’s approach signals a shift from voluntary to mandatory climate accountability [4].

Understanding SB 253 and SB 261

SB 253 (Climate Corporate Data Accountability Act) そして SB 261 (Climate-Related Financial Risk Act) each target distinct but complementary aspects of climate disclosure:

• SB 253 requires public and private companies with total annual revenues over $1 billion and doing business in California to report Scope 1, 2, and 3 GHG emissions.
• SB 261 mandates companies with annual revenues exceeding $500 million to prepare biennial reports detailing 気候関連の金融リスク and measures taken to mitigate them [1][2].

Together, these bills represent a holistic approach to climate transparency, quantifying emissions on the one hand and mapping out risk exposure on the other.

Timeline and Compliance Requirements

The California Air Resources Board (CARB) is tasked with implementation. Key compliance milestones are as follows:

Requirement Type	SB 253	SB 261
Company Revenue Threshold	> $1 billion	> $500 million
First Report Due	2026 (Scope 1 and 2)	2026 (first risk report)
Scope 3 Reporting Deadline	2027	該当なし
Verification Requirement	Third-party assurance (phased)	No third-party assurance
Reporting Frequency	Annually	Biennially
Public Disclosure Platform	Yes (CARB)	Yes (CARB or company website)

[4][5]

SB 253: Mandatory GHG Emissions Disclosure

SB 253 establishes mandatory, public, and standardized disclosure of corporate GHG emissions, including:

• スコープ1: Direct emissions from owned/controlled sources.
• スコープ2: Indirect emissions from purchased electricity.
• スコープ3: All other indirect emissions in the value chain (e.g., supply chain, product use) [1][4].

The legislation explicitly adopts the GHGプロトコル as the methodological framework and requires companies to obtain third-party assurance of their disclosures. Assurance for Scope 1 and 2 begins in 2026, and for Scope 3 by 2030, with CARB defining the technical parameters [5].

The inclusion of スコープ3排出量 is particularly notable. Often comprising over 70% of a company’s total emissions footprint, Scope 3 has historically been excluded from mandatory U.S. disclosures due to measurement complexity. California’s move aligns with global best practices.

SB 261: Climate Financial Risk Transparency

SB 261 shifts the lens to climate risk. It compels companies to publish a biennial report identifying:

• Material climate-related financial risks (both physical and transition-related).
• Strategies and measures adopted to mitigate such risks.

The bill requires alignment with TCFD guidelines, though it does not impose a mandatory format. It emphasizes forward-looking risk management over backward-looking emissions inventory [2][6].

Companies may leverage existing climate reports for compliance, provided they cover all required elements and are made publicly accessible. Unlike SB 253, SB 261 does not require third-party verification, a deliberate decision to reduce compliance burdens while promoting transparency.

Strategic Implications for Corporates

Compliance with SB 253 and SB 261 will demand significant operational and governance shifts, especially in value chain data collection and climate risk governance. Strategic considerations include:

• Data Infrastructure: Companies must invest in emissions tracking and climate scenario modelling tools.
• Supply Chain Engagement: Particularly for Scope 3, firms will need to coordinate with suppliers and distributors.
• Governance Alignment: Risk oversight will need to shift from ESG teams to enterprise-wide risk management functions.
• Investor Communication: These disclosures will likely influence investor assessments and financing terms.

California vs. Global Standards: A Comparative Lens

Element	California (SB 253 / SB 261)	CSRD (EU)	SEC Proposed Rule (U.S.)
Scope 3 Mandatory?	Yes (SB 253, phased)	Yes	Partially (if material)
Risk Disclosure Standard	TCFD (SB 261)	ESRS/TCFD under CSRD	TCFD
Third-Party Assurance	Yes (SB 253)	Yes (phased)	Yes (limited, phased)
Applies to Private Companies	Yes	Yes	No

[1][2][4][5][6]

California’s framework echoes many CSRD and SEC elements but goes further in its applicability to private firms and its strict Scope 3 timeline. It sets a national precedent, likely accelerating federal and state-level adoption.

Emerging Challenges and Criticisms

Despite strong momentum, implementation challenges persist:

• データの品質と可用性: Particularly for Scope 3, data gaps and inconsistent reporting standards could hinder comparability.
• Compliance Costs: Smaller firms may struggle to absorb compliance-related expenses.
• Legal Risks: California’s laws may face judicial challenges around extraterritoriality or federal pre-emption.

Still, the regulatory direction is clear: climate transparency is no longer optional.

Recommendations for Companies

To prepare effectively, companies should:

1. Map GHG Inventory: Begin with a full Scope 1-2-3 inventory under the GHG Protocol.
2. Develop a Risk Assessment Framework: Align with TCFD to identify and disclose physical and transition risks.
3. ステークホルダーの参画: Work with suppliers, investors, and internal teams to align expectations.
4. Establish Internal Controls: Prepare for assurance by integrating climate metrics into existing financial controls.
5. Stay Current: Monitor CARB guidance and stakeholder consultations [5][6][7].

For companies already pursuing forward-looking emissions strategies such as avoided emissions, these regulations provide a baseline from which to build broader impact narratives.

最終的な感想

California’s SB 253 and SB 261 reflect a transformative step in the maturation of climate-related corporate governance. By uniting emissions transparency with financial risk disclosure, the state is signalling a broader shift toward integrated, mandatory ESG reporting. For businesses, the message is clear: align now, or risk being left behind.

参考文献

[1] https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202320240SB253
[2] https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202320240SB261
[3] https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202320240SB219
[4] https://ww2.arb.ca.gov/our-work/programs/california-corporate-greenhouse-gas-ghg-reporting-and-climate-related-financial
[5] https://ww2.arb.ca.gov/sites/default/files/2025-08/SB%20253%20261%20workshop%20slides%208-21.pdf
[6] https://www.insideenergyandenvironment.com/2025/05/key-takeaways-from-california-air-resources-boards-public-workshop-on-implementing-california-climate-disclosure-laws-sb-253-and-sb-261/
[7] https://corpgov.law.harvard.edu/2025/07/15/california-climate-accountability-getting-started-on-sb-253-and-sb-261-reporting/