Scientific literature increasingly recognizes air quality (AQ) and climate change (CC) as two interconnected issues since many of the same sources are responsible for both greenhouse gas (GHG) emissions and air pollutants. This overlap means that integrated strategies could result in relevant synergies covering not only environmental issues but also social, economic and public health-related implications. This research explores how air-climate integration is approached within a multi-level governance framework, with a focus on identifying the main factors driving upscaling dynamics. To support this, the study emphasizes the importance of knowledge exchange among cities (horizontal upscaling) and engagement with regional governments to both enhance the conditions for replicability (vertical upscaling) and establish binding standards across municipalities (hierarchical upscaling). Targeting resilient, carbon-neutral and healthy cities, the results provide insights into a better understanding of how well-performing climate actions can be multiplied, accelerated and broadened to pursue a more effective air quality and climate integration.