Net‐zero carbon declarations by Japanese local governments: What caused the domino‐like diffusion?

Sub‐national governments are a crucial non‐state actor for mitigating climate change. This importance has recently strengthened as increasing numbers of municipalities declare net‐zero carbon emission goals to support the Paris Agreement, often well ahead of national governments. In Japan, net‐zero declarations have also diffused widely, with nearly 800 declarations appearing in domino‐like fashion over 2019–2022. To elucidate the factors that propelled this rapid diffusion, we used an event‐history analysis based on data from a survey to develop an integrated statistical model. We then deepen understanding of diffusion mechanisms through seven brief case studies informed by interviews and document analysis. We find that the drivers of policy diffusion varied over time. During the early stage, internal factors drove the spread of declarations; namely participation in transnational city networks, endowed human and financial resources, and political leadership. But in later stages, diffusion was mostly propelled by external factors; namely declarations by neighboring cities and the affiliated prefectural government. Through these findings, we contribute to scholarship through two novel perspectives. First, we reveal the factors driving policy diffusion across both early adopters and the ordinary majority. Second, we show how the influence of well‐known factors can vary during different stages of policy diffusion. 地方政府是缓解气候变化的重要非国家行动者。随着越来越多的城市(通常远远领先于国家政府)宣布净零碳排放目标以支持《巴黎协定》，这一重要性最近得以加强。在日本，净零排放声明也广泛传播，在2019–2022年间以类似多米诺骨牌的方式出现了近800项声明。为了阐明这一快速传播的推动因素，我们使用基于调查数据的事件历史分析，提出一项综合统计模型。我们随后通过访谈和文献分析所提供的七个简短案例研究，加深了对扩散机制的理解。我们发现，政策扩散的驱动因素随时间推移而变化。在早期阶段，内部因素推动了声明的扩散，即跨国城市网络的参与、所获得的人力资源和财力资源、以及政治领导力。但在后期阶段，扩散主要由外部因素推动，即邻近城市和附属地政府的声明。通过这些发现，我们透过两个新颖的视角为学术作贡献。第一，我们揭示了在早期采纳者和普通大众中推动政策传播的一系列因素。第二，我们证明了熟知因素的影响力如何在政策扩散的不同阶段发生变化。 Los gobiernos subnacionales son un actor no estatal crucial para mitigar el cambio climático. Esta importancia se ha fortalecido recientemente a medida que un número cada vez mayor de municipios declara objetivos de emisiones netas de carbono cero para apoyar el Acuerdo de París, a menudo mucho antes que los gobiernos nacionales. En Japón, las declaraciones de cero emisiones netas también se han difundido ampliamente, con casi 800 declaraciones que aparecieron en forma de dominó durante 2019–2022. Para dilucidar los factores que impulsaron esta rápida difusión, utilizamos un análisis de historial de eventos basado en datos de una encuesta para desar