2015 was an important year for C40, and for our mayors. We saw cities firmly establish their place in the global dialogue on climate change, from gathering at the Vatican to committing in large numbers to the Compact of Mayors, culminating in a fantastic series of events at COP21 in Paris. On top of these milestones, 2015 also marked C40’s 10th anniversary. Throughout the year C40’s 10 Years of Results series featured contributions from our mayors, partners, international political figures and global thought leaders. Below we take a look back through a very productive and exciting year.  

C40 Executive Director Mark Watts kicked off our 10th anniversary year, reflecting on the growth of C40 and Celebrating 10 Years of Results. We also took a look back on 10 Defining Moments in C40 History.

As a data-driven organization, C40 loves to talk numbers. This month we shared the 10 most important metrics of 2015.

This month C40 Chair and Rio de Janeiro Mayor Eduardo Paes told us why 2015 will be a critical year for C40 as well as his city, and discussed the creation of the Compact of Mayors and how committed cities are leading the way in filling the emissions reductions gap.

In a video address, special guest 42nd President of the United States William J. Clinton looked back fondly on his participation in C40 over the years and congratulated the organization on becoming the preeminent network of cities working to address climate change.


A photo posted by C40 (@c40cities) on

Following on the success of our first-ever Latin American Mayors Forum, we also looked at 10 ways that Latin America is driving climate action.

This month we featured a video message from World Resources Institute President & CEO Andrew Steer, who wished C40 a ‘Happy Birthday’ and reflected upon the impact C40 has had over the last ten years.

In 2015, C40 continued to expand its reach through our social media channels, where we post the most important news about cities and climate change. To honour another successful year on Twitter (a big ‘thank you’ to our more than 29,000 followers!), we shared 10 of our favourite Twitter handles to follow. Don’t forget to join the conversation and follow @c40cities and the hashtag #ycities for updates.

We featured a guest post from UNFCCC Executive Secretary Christiana Figueres, who applauded C40 for ten years of excellent work, discussed some of the co-benefits of climate action already experienced across the world, and called for the scaling up of climate action.

To commemorate C40’s 10th Anniversary, we launched a new booklet celebrating 10 years of climate action and showcasing our vision for a bright, urban future. We also heard from Deputy Mayor of London for Environment & Energy, Matthew Pencharz, who highlighted some of C40’s best accomplishments in London.

We featured two guest posts as part of our Mayors Voices series, one from Addis Ababa Mayor Deriba Kuma commending C40 on reaching this 10 year milestone, and one from Lord Mayor of Copenhagen Frank Jensen on Copenhagen’s achievements, and plans for further progress.   

We also featured a video message from the UN Secretary-General’s Special Envoy for Cities and Climate Change Michael R. Bloomberg, who discussed the importance of cities and city leaders in tackling climate change and congratulated C40 on 10 years of results. 

In the final post of our ’10 Years of Results’ series, we heard from former C40 Chair and Mayor of Toronto David Miller, who reflected upon his time at C40 and the past decade of achievements, and highlighted the importance of C40’s Climate Action in Megacities 3.0 report in helping mayors set and achieve ambitious targets. 

2015 has been an incredible year for C40. Thank you to those who contributed and congratulated – we’re looking forward to another exciting year following the successful COP in Paris, and to another ten years of helping to make cities healthier, wealthier and more sustainable places to live for urban citizens everywhere.  

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