By John Baimba Sesay
Rio in Brazil was buzzed with energy as over 300 mayors from around the world gathered for the C40 World Mayors Summit, held from 3–5 November 2025. A key precursor to COP30, the summit of mayors and global climate leaders provided a platform for city to share solutions, forge partnerships, and discuss how to accelerate bold, city-led climate action toward a sustainable and resilient urban future.
Across plenaries, closed-door dialogues, and strategic discussions, mayors emphasised the urgent need for direct access to climate finance, inclusive green transitions, and stronger city-national collaboration.
This call is crucial: while cities produce over 70% of global emissions, they currently receive less than 10% of available climate funding. Equitable investment flows are needed to empower local governments to tackle urgent challenges such as flooding, waste management, and extreme heat, which already threaten millions of lives across African cities. Yes, Africa!
The scale of the challenge is also stark. Studies by C40 Cities and the Mayors Migration Council (MMC) project that by 2050, up to eight million people could migrate to just ten Global South cities due to climate-related risks. Freetown alone could receive around 269,000 internal climate migrants under higher-emission scenarios, while Karachi could see as many as 2.3 million if global warming exceeds 1.5°C.
Yet there is reason for optimism. A global survey of 130,000 people across 125 countries found that 89% want their governments to do more on climate. To meet this demand, cities must have direct access to funding for adaptation, resilience, and loss and damage, while national governments must mobilise US$1.3 trillion annuallyin climate finance, prioritising urban and subnational contexts where solutions protect lives most effectively.
The scale of investment required is also massive: global urban infrastructure needs range from USD 4.5–5.4 trillion per year, yet only a fraction aligns with climate goals. Developing countries alone require at least USD 384 billion annuallyin urban climate finance to meet the Paris Agreement targets.
Unlocking urban investment has the propensity to unlocks climate ambition. Empowered cities mean empowered residents and that is how the world builds a resilient, inclusive, and low-carbon future.
But there are other positives; Cities are already demonstrating leadership. Nearly 100 C40 cities, representing 700 million residents, have climate investment plans capable of removing nearly 400 million cars off the road for a year.
From Lagos’s waste-to-energy PPP, London’s fossil-free pension fund and Ultra Low Emission Zone, to Freetown’s over $90m cable car project, cities show that robust governance, innovative finance, and credible climate plans can deliver measurable impact and attract investment.
The Rio summit reinforced a vital truth: cities especially in the Global South are not just participants, they are leaders, shaping a just, climate-resilient future on the road to COP30.
