The Global Covenant of Mayors for Climate & Energy (GCoM) is a coalition that brings together city and local-government climate initiatives, including the EU Covenant of Mayors and the Compact of Mayors. It was announced in Mexico City on 1 December 2016, with Michael R. Bloomberg and then-European Commission Vice-President Maroš Šefčovič among its founding leaders.6 Its global secretariat is based in Brussels, Belgium.4
GCoM’s purpose is to help local governments turn climate commitments into measurable action. Its approach combines support for city planning with common reporting: participating cities track greenhouse-gas emissions, climate hazards and vulnerabilities, and develop mitigation and adaptation plans. The alliance also works through regional and city networks, national governments and other partners, with technical support covering reporting, finance, research and communications.511
The alliance’s scale has grown substantially. Its website reports more than 14,000 participating cities and local governments across 148 countries, representing over 1.2 billion people.4 The supplied homepage excerpt gives a current headline figure of 14,141 cities and more than 100 global partners. A 2025 impact report, meanwhile, describes more than 13,800 participating cities and estimates that their actions could reduce global emissions by up to 4.5 gigatonnes of CO₂ annually by 2050.2 These figures reflect different reporting snapshots and should not be treated as identical measures.
GCoM’s work also includes research and investment support. Its 2025 materials report that cities are disclosing climate projects through the CDP–ICLEI Track, while the alliance’s reporting highlights the potential for city action to contribute to emissions reductions and resilience.92 The organization’s stated role is to connect local climate leadership with data, finance and partnerships, rather than to implement every city project itself.4