A Review of Multi-scale Analytical Approaches to Assessing the Impact of Urban Morphology on CO₂ Emissions

The significant impact of urban morphology on CO₂ emissions is widely recognised. However, existing studies exhibit considerable variations in findings and conclusions. These discrepancies stem from differences in research scales, selected urban morphology factors, CO₂ inventory data, and analysis methods, hindering the development of robust and generalizable knowledge. These discrepancies underscore the need for a comprehensive synthesis to identify the root causes of inconsistency and comparable results. This review synthesises 408 articles to address these discrepancies. Key findings include the identification and categorisation of 147 urban morphology factors into six groups (e.g., building embodied, transport operational, tangible production), and the development of a multi-scale factor selection framework. The identification of 'tele-connection' factors as a primary source of cross-scale inconsistency. Moreover, a comparative assessment shows that uncertainties across nine CO₂ inventory datasets remain below 20%. Crucially, an integrated multi-scale framework is developed and proposed, which provides a systematic procedure for selecting factors, methods, and inventory data specific to research different scales. This synthesis not only clarifies the root causes of variation within the field but also provides an actionable path toward more reliable, comparable, and policy-relevant research outcomes.