Small cities can achieve great accomplishments: Transnational climate actions and carbon emissions – Evidence at the city level

Strategies for addressing climate risk are commonly developed at the national level, often overlooking the role of cities as the actual implementers of specific actions. We examine the contributions of urban actions to transnational climate initiatives by investigating cities that have joined the European Union Covenant of Mayors for Climate and Energy Initiative (EUCoM), which aims to reduce global greenhouse gas emissions. Adopting a city perspective enables us to observe the micro mechanisms through which transnational climate actions make a difference. Using a stacked difference-in-differences strategy, our analysis reveals that joining the EUCoM leads to an 8.6 % reduction in carbon dioxide emissions, which also spills over to neighboring cities. This positive impact persists for 3–5 years. The effect of joining the initiative is more pronounced in coastal and densely populated cities, whereas spatial spillover effects weaken beyond a distance of 30 km. Moreover, the spatial linkages between cities significantly influence local authorities' decision to participate in the initiative and may result in an “joining for appearance” phenomenon. Importantly, self-reported emission inventories reflect cities' ambitions and capacities for emission reduction, but there is a disconnect between their mitigation performance and ambitious emission reduction goals. • Quantifying the contribution of signatories in transnational climate action (EUCoM) using stacked DID Models. • Machine learning approach to construct and validate the dataset. • There are spatial contagion and clustering effects of urban behavior in EUCoM. • There is a disconnect between emission reduction performance and emission reduction targets. • Signatories' willingness and determination are key factors in moving beyond specific emission reduction measures.