Aggregating the Impacts of Non-State and Subnational Climate Actions: An Exploration of Methods

The document provides guidance on the methodological assumptions required to aggregate the climate mitigation impacts of cities, businesses, and states. It emphasizes that variations in assumptions—such as the scope of included actions and the degree of conservativeness—significantly influence the credibility and comparability of assessment results. The paper aims to enhance transparency in reporting and support users of the ICAT Non-State and Subnational Action (NSA) Guide and the Climate Action Aggregation Tool (CAAT) in making informed design choices for their assessments.

• Methodologies for calculating the collective impact of multiple non-state and subnational actors are still evolving and require specific assumptions to accurately determine potential emission reductions and prevent double-counting or overlaps between different actors.
• The choice of assumptions regarding the scope of actions and the level of conservativeness directly affects the results of an assessment; a broad scope may show higher potential reductions but risk including unachievable actions, while high conservativeness may produce more realistic results but exclude ambitious actors needing support.
• Transparent communication of methodological assumptions is essential because studies that appear comparable by using the same actor groups or following the same ICAT NSA guide steps may actually produce different results due to differing underlying assumptions.
• The Initiative for Climate Action Transparency (ICAT) provides a step-by-step Non-State and Subnational Action (NSA) Guide and an excel-based Climate Action Aggregation Tool (CAAT) to help national policymakers and analysts collect data and assess the impact of these actions.

APA

World Resources Institute (n.d.). Aggregating the Impacts of Non-State and Subnational Climate Actions: An Exploration of Methods. https://www.wri.org/research/aggregating-impacts-non-state-and-subnational-climate-actions-exploration-methods

Chicago

World Resources Institute. Aggregating the Impacts of Non-State and Subnational Climate Actions: An Exploration of Methods. n.d. https://www.wri.org/research/aggregating-impacts-non-state-and-subnational-climate-actions-exploration-methods.

Wikipedia

{{cite report |author=World Resources Institute |title=Aggregating the Impacts of Non-State and Subnational Climate Actions: An Exploration of Methods |url=https://www.wri.org/research/aggregating-impacts-non-state-and-subnational-climate-actions-exploration-methods |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{worldresourcesinstitutendaggregating, author = {{World Resources Institute}}, title = {{Aggregating the Impacts of Non-State and Subnational Climate Actions: An Exploration of Methods}}, institution = {World Resources Institute}, url = {https://www.wri.org/research/aggregating-impacts-non-state-and-subnational-climate-actions-exploration-methods}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }