From case studies to climate action plans: an assessment of the efficacy and integrity of subnational climate action

Momentum is building in non-state climate action, evidenced by the increasing number of climate pledges from cities, states, and regions around the world. Subnational governments can play a pivotal role in global efforts to avoid the worst impacts of climate change and limit warming to 1.5°C or below, yet the integrity of their commitments and plans remains uncertain. We address these critical questions through two related studies focused on understanding the efficacy of subnational climate action: a meta-analysis of mitigation case studies and a qualitative assessment of city climate action plans.

Based on a prior systematic literature review and synthesis of 234 subnational climate change mitigation case studies from peer-reviewed literature to understand the effectiveness and reliability of various subnational mitigation strategies and policy instruments, we found that there are substantial differences in the size and certainty of expected impacts from different mitigation strategies. A wide range of mitigation strategies are used in cities and regions, and misalignment exists between the strategies with the highest expected impacts and those that are most frequently implemented by policymakers.

This disconnect motivates the need for further research to understand subnational governments’ choices over mitigation strategies and the implications of these choices for the credibility of subnational climate action. Here, we introduce a framework for evaluating the transparency and integrity of city climate pledges and plans and present initial findings for Global North cities. This analysis will enable us to identify best-practice strategies for cities, highlight areas of weakness, and assess interactions between mitigation and other climate goals. Together, these studies provide the groundwork for more systematic, quantitative evaluations of integrity in subnational climate action and contribute to the ongoing discussion of the role of subnational governments in achieving global climate goals.