Five years ago, during my second term as mayor of Paris, our urban planning agency projected the city would experience 20.5 tropical nights – where temperatures stay above 20 degrees by 2050.
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This summer has already seen 28 degrees, a quarter century ahead of schedule. And recently, thousands of miles away, the Himalayas told a similar story: glacial collapse triggered flash floods of a scale Nepal and Tibet had never seen, overwhelming homes, infrastructure, and communities built for a different climate.
This is what climate overshoot looks like. The UN Environment Programme’s latest report, Limiting Overshoot, makes clear that every city will feel it: longer heat waves, more intense flooding, and rising energy costs, with low-income cities bearing the heaviest burden. But overshooting does not mean defeat. It means we must move faster, and more than a decade of experience has taught us exactly how: by working together.
The report underscores why: flexible, multilevel governance is essential to implementing deep mitigation measures while managing growing climate risks. As global ambassador for the Global Covenant of Mayors (GCoM), I am proud to be part of the world’s largest alliance of local climate leaders – spanning more than 14,000 cities and local governments across 150 countries – who could reduce their annual emissions by 4.5 gigatonnes of carbon dioxide equivalent by 2050, equivalent to removing about 1 billion gasoline-powered vehicles for one year.
For over a decade, since the Paris Agreement was signed, cities have been implementing policies, incubating solutions, and driving emissions down, showing that when cities and national governments work together, we can deliver at the scale this moment demands. We cannot afford to work in silos. Where that coordination exists, we know what is possible.
As mayor, I actively advocated to secure a formal role for local governments in global climate governance, beginning with COP21 in Paris in 2015. Eleven years later, the Coalition for High Ambition Multilevel Partnerships (CHAMP) is turning that vision into reality, embedding multilevel governance as a working part of Paris Agreement implementation.
Through CHAMP, Brazil and Germany are now leading a group of 77 countries and the European Union who are committed to genuine national-local collaboration, at a moment when international cooperation itself is under pressure.
Last year, in Brazil, I witnessed first-hand what this kind of collaboration can achieve. Ahead of COP30 in Belém, the Brazilian government called for a “global mutirão,” borrowing an Indigenous Tupi-Guarani concept for a collective, community wide effort. Domestically, Brazil is proving what this spirit achieves: GCoM, C40 Cities, and federal partners are working together to deploy electric buses in Belo Horizonte, fund municipal composting in Curitiba and Ananindeua, and scale food waste reduction across Rio Grande do Sul.
This kind of multilevel cooperation has the potential to unlock two critical levers to accelerate the green transition and make communities more resilient to climate impacts: finance and innovation. Cities in the global south – despite their low emissions contributions – face the most severe climate impacts and compounding challenges. Looking ahead to COP32 in Addis Ababa, Ethiopia has a chance to convert its host nation status into lasting leverage for Africa’s climate finance agenda that recognises African cities, which are already leading on the ground, as central actors in this issue.
More broadly, cities all around the world need easier and more direct access to climate finance to mitigate both the financial and human cost incurred by future disasters. The economic logic is clear: every dollar invested in making infrastructure disaster-resilient saves society an average of four in future recovery costs. And yet, less than 10 per cent of global climate finance reaches cities and local governments directly, even though they are responsible for, and hold the solutions to, over 70 per cent of global emissions.
This imbalance is not just a technical funding gap. It’s a coordination gap that countries like Morocco are already closing. Since becoming a CHAMP member, the Moroccan government has worked to establish a dedicated national program for subnational climate action. This ensures that climate initiatives across its regions and communes have access to project preparation, financial planning, technical capacity building, and other mechanisms that enable local leaders to turn local ideas into real results for local communities.
This financing also allows cities, which are hubs for research institutions, infrastructure networks, and engaged communities, to become laboratories for new climate solutions. Reaching net zero will require not only deep and rapid emissions cuts, but harnessing nature, one of our most powerful tools for resilience, as both a carbon dioxide removal solution and a built-in defence against climate impacts.
Today, one in seven people worldwide lives in a village, town, or city taking decisive action on climate through GCoM. This global alliance – and our ability to scale mitigation and adaptation solutions together – form the backbone of delivering on the Paris Agreement.
Effective cooperation between local and national authorities is not optional. When cities and nations design climate action together, it works. The last decade has proven it. And we cannot afford to let disinformation manufacture doubt where trust is needed between national and local governments. Overshooting 1.5 degrees is not a defeat. It is a call to action – no amount of denial or disinformation can change this reality. National governments, multilateral institutions, and cities must act together, faster, and with far greater ambition than we have shown so far. This is what CHAMP shows is possible. And it is the work of the next decade.
