## 1 Introduction  
Over more than a decade, climate change has become one of the main concerns for 68% of Europeans [1], which, together with the confirmation of the effect that cities have on the global emissions of greenhouse gases (GHG) [2] (with 2% of the Earth's surface generating between 31% and 80% of such gases at global level [3]), has led to the transformation of international political agendas in recent years [4]. Within the framework of the European 20-20-20 targets [5], which set a reduction of 20% of the European Union's GHGs, an increase to 20% of energy consumption being based on renewable resources and the improvement of 20% of energy efficiency in general terms by 2020, a major municipal-level initiative called \"The Covenant of Mayors\" (CoM) was launched in January 2008 and updated in October 2015. It arose to support the efforts of local entities regarding the implementation of a Sustainable Energy Action Plan (SEAP) and to support their contribution to the mitigation of emissions. The seminal and probably most important idea of the CoM is the exchange and application of best practices between European cities and towns [6]. The initiative takes advantage of the resilience and ingenuity of individual cities as they pursue ambitious policy [7], while up-scaling such achievements through the constitution of European transnational network [8]. In 2014, the EU updated its 20-20-20 targets [9], intensifying its commitments, albeit in a non-binding way for the countries involved. The Commissioner for Climate Action considered that, together with the reduction of GHG to mitigate climate change, the European Union needed to strengthen its resilience to the unavoidable effects of climate change [10]. The path had already been paved in The European Commission White Paper 2009, \"Adapting to climate change: Toward a European framework for action\" [11]. According to [PERSON] and [PERSON], we mitigate climate risk-cutting GHGs emissions to reduce the likelihood of adverse environmental or climatological conditions, and we adapt to climate risk by modifying production and consumption decisions to reduce the severity of adverse environmental or climatological conditions should they occur [12]. To address this incipient need to boost adaptation, on 16 October 2014, the European Commission's Directorate General for Climate Action launched a new, local initiative called Mayors Adapt (MA), which should coexist with pre-existing programs such as LIFE (L'Instrument Financier pour l'Environnement) [13] or CoM. Even before the official constitution of the MA, the European Committee of the Regions (CoR) recommended the consolidation of municipal programs for the exchange of good practices, such as the CoM, as well as the promotion of new ones [14], such as the MA, highlighting the key role of the local level, as well as the relevance of forums for the exchange of ideas, guaranteeing policy coherence and synergies between the different initiatives. While the CoM focuses on the reduction of GHG, which is a clear mitigation strategy, the MA is endeavored to the adaptation of cities to the effects of climate change. In spite of their well-defined objectives and clear strategic differences, in 2015, the CoM and the MA merged into the Covenant of Mayors for Climate and Energy (CoM-C&E), the latter being integrated in 2016 with the Compact of Mayors (a trans-European initiative) in what would then be named the Global Covenant of Mayors for Climate and Energy (GCoM), with a clear global aspiration beyond European borders. This process of transformation and integration with other initiatives, until the current GCoM, has not been exempt from controversy, being considered by some authors as an incomplete initiative [15].