A contingent diffusion model of local climate change policy adoption: Evidence from Southern California cities

Climate change policy is an essential driver of urban sustainability, yet minimal research has examined how they emerge and spread across cities in shared metropolitan areas. While policy diffusion or policy mobility theories could explain the aforesaid, much of the international scholarship have not utilized an amalgamation of these two complementary theoretical perspectives. As a result, we lack a comprehensive understanding of the regional dynamics and spillover effects local governments can generate for urban sustainability. This article proposes a contingent diffusion model to examine the intra-regional adoption of local climate action plans within Southern California from 2000 to 2018. We find that neighboring jurisdictions that adopt climate policy increase the likelihood of a home city's adoption. Yet, neighboring effect is contingent on the home city's existing proenvironmental policy propensity. However, in contrast to conventional wisdom, this study finds no evidence that local environmental advocacy groups play a crucial role in the diffusion of municipal climate initiatives. Altogether, the results suggest that a regional diffusion model of policy innovations is more likely successful when adaptive capacity is in place to facilitate green infrastructure. These findings provide implications for policymakers and planners who want to achieve successful spillovers of urban climate policies across local governments.