Compact of Mayors: The biggest collaboration to accelerate climate action

The Compact of Mayors is an ambitious agreement by mayors and other city officials to publically commit to deep GHG emissions reductions -- making existing mitigation and adaptation targets and plans public and report on their progress annually -- using a newly-standardized measurement system that is compatible with international practices. Through this initiative, cities will be choosing to meet the same requirements proposed for the international climate negotiations that will lead to a global climate treaty in 2015. The Compact of Mayors was launched on September 23, 2014, at the UN Secretary General’s Climate Summit in New York City by the C40  Cities Climate Leadership GroupICLEI  Local Governments for Sustainability, and UCLG  – endorsed by UN-Habitat, UN Secretary General´s Special Envoy for Cities and Climate Change, UN Secretary General´s Climate Change Support Team.

447 cities, representing 390,761,581 people worldwide and 5.39% of the total global population, have committed to the Compact of Mayors.

The Compact of Mayors aims to:

  • Enable recognition of new and existing4 city-level commitments through the Compact by making annual reporting data on local climate action publically available;
  • Establish robust and transparent data collection standards;
  • Commit to common reporting processes for local climate action that allow for consistent and reliable assessment of progress towards meeting those targets;
  • Create an evidence base of the greenhouse gas impact of city action to enable capital flows into cities to support city governments taking further action and to be held responsible for that action and the associated investments;
  • Demonstrate the commitment of city governments to contribute positively towards more ambitious, transparent, and credible national climate targets by voluntarily agreeing to meet standards similar to those followed by national governments; and
  • Encourage national governments to actively support additional city action by recognizing local commitments, establishing more enabling policy environments and directing resources to cities to limit any further increase in global warming and to appropriately resource both mitigation and adaptation local climate action.


Addressing climate change entails making our cities more knowledgeable about their own consumption and resilience. The Compact will contribute to that,” said Kadir Topbaş, Mayor of Istanbul and President of UCLG.

Historic Partnership Between the Compact of Mayors and the Covenant of Mayors

During COP21 and in conjunction with the Climate Summit for Local Leaders, Michael R. Bloomberg, UN Secretary-General’s Special Envoy for Cities and Climate Change, founder of Bloomberg LP and former mayor of New York City, and European Commissioner for Economic and Financial Affairs, Taxation and Customs and Former Finance Minister of France Pierre Moscovici, announced that the Compact of Mayors and the Covenant of Mayors will formally partner to promote and support voluntary city action to combat climate change. The partnership between the Compact of Mayors and the Covenant of Mayors, the European Union’s initiative of several thousand local governments assuming the responsibility of tackling climate change in their territories, will open a new chapter to demonstrate the global impact of local city action.

Join the Compact of Mayors! 

You can use this template letter to send back to us to express your commitment.

Data collected through the Compact will underscore the importance of considering cities’ climate efforts as nations set GHG reduction targets with the ultimate goal of reaching an ambitious, binding, international climate agreement.

Under the Compact, the carbonn Climate Registry will serve as the designated central repository that will enable the compilation of data through existing national, regional, and global city reporting platforms, such as CDP Cities. We are also in early stages of exploring the possibility of aligning with other reporting platforms such as the European Covenant of Mayors– with the overall goal of reducing the need for cities to report more than once.  We will work collaboratively to aggregate these individual efforts across thousands of cities who make up C40, ICLEI and UCLG with the aim of capturing their global impact.