How are cities using sustainable transport to clean our air?

Credit: C40 Cities

The United Nations’ International Day of Clean Air for blue skies highlights a fundamental human right that so many people are denied — the right to breathe clean air.

Around nine in ten people around the world breathe dirty air every day, which not only leads to avoidable health issues…


By Mayor of Barcelona and Vice-Chair of C40 Cities Ada Colau.

Ajuntament Barcelona on Flickr. This was originally published in Metropolis on 11 October 2021.

The recent report by the Intergovernmental Panel on Climate Change (IPCC) was abundantly clear — climate change is a dire threat to humanity. Ignoring the science or failing to take real action to combat this crisis is simply not…


By Mark Watts, Executive Director of C40 Cities, and Julia Lipton, Director of Climate Action Planning and Innovation at C40 Cities

© Alexis Gonzalez / Getty Images

Last month’s Intergovernmental Panel on Climate Change report — labelled ‘code red for humanity’ — has been one headline in a summer of bad news about the climate, as…


Ahead of COP26, we, the C40 Global Youth & Mayors Forum, call on national governments to take radical action within the next year to address the climate crisis, in line with at least halving global emissions by 2030.

The science is clear — we must collectively at least halve global emissions by 2030 — and Global North countries must go further and faster to reduce their fair share of emissions. If we allow greed for more money, power and oil to prevent us reaching this goal, we will…


By Mark Watts, Executive Director, C40 Cities

© eyesfoto — Getty Images

Today 15 of the world’s most influential mayors — all members of the C40 Cities network — are setting out how they will power a green and just recovery from the COVID-19 pandemic. By setting ambitious targets for accelerating the full decarbonisation of…


Data: a foundation for cleaner air

Credit: Open-Seneca, C40 Cities

C40 cities are working to clean the air that we breathe. As part of their commitments to the C40 Clean Air Cities Declaration, cities are taking bold, innovative steps towards making air pollution a thing of the past, and guaranteeing their populations can breathe healthy, clean air.

Nine out of…


How cities are focusing on renewable energy and buildings to provide cleaner air

Credit: C40 Cities, City of Oslo

To mark the second United Nations’ International Day of Clean Air for blue skies, we are highlighting the action being taken by cities around the world to ensure everyone, everywhere can breathe clean air.

Here we focus on three ways that cities can reach the goals set out in the


Nature breathes life into our cities. As part of a new campaign to highlight the importance of urban nature to our everyday lives, C40 has invited mayors, artists, cultural influencers and other thought leaders from cities around the world to write a ‘Letter to Nature’.

Read what Mayor of Cape…


The latest report from the Intergovernmental Panel on Climate Change contains irrefutable scientific evidence for what C40 mayors already know: that climate breakdown will make major cities uninhabitable if we don’t cut greenhouse gas emissions immediately.

Some of the changes to our climate are irreversible and as the Climate Crisis…


On behalf of C40 Cities, I would like to thank the Intergovernmental Panel on Climate Change for its Working Group 1, 6th assessment report, which sets the gold standard for climate science.

The evidence laid out in these pages confirms what we are all witnessing each and every day. The…

C40 Cities

C40 is a leading global network of cities taking bold and ambitious climate action to deliver a healthy, equitable and sustainable future for all.

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