In cities worldwide, low-carbon urban initiatives (LCUIs) are realised by pioneers that prove that climate mitigation strategies can be integrated in urban development trajectories. Practitioners and scholars reflect on the need to scale-up such initiatives in order to accelerate the transition to low-carbon cities. Yet, limited conceptual clarity exists regarding the meaning of the concept of ‘scaling-up’ and the factors driving this process. This article aims to contribute to practice and theory on low-carbon urban development by presenting a taxonomy on the concept of scalingup. Moreover, an explanatory framework is presented consisting of factors expected to contribute to the impact and scaling-up of LCUIs. Two case studies were conducted to illustrate the explanatory framework. The studies are illustrative but suggest that the explanatory framework allows for a systematic understanding of how the impact of former initiatives can be explained, and how their scaling-up can be promoted. 在全球各个城市，先驱者们实施了低碳城市举措（LCUI) ，证明气候缓解战略可以融入城市发 展轨迹。从业人员和学者反思需要扩展这些举措，以加快向低碳城市的转型。然而，关于“扩 展” 概念的意义和驱动这一过程的因素，其概念清晰度依然有限。本文旨在通过提出“扩展” 概念的分类法，为低碳城市发展的实践和理论做出贡献。此外，本文提出了一个解释性框架， 纳入了有助于扩大LCUI影响和扩展LCUI本身的因素。我们开展了两项案例研宄来说明这一解 释性框架。这些研宄是说明性的，但表明该解释性框架能便于系统地了解如何解释先前各项举 措的影响，以及如何扩展其规模化影响。