Ten Years After Paris: Climate Action Depends on Cities

In December 2015, COP 21 made Paris the beating heart of the world. With its universal scope and the immense expectations it raised, this climate summit represented a historic moment of unity in the face of climate change. For the first time, 195 countries agreed on a common framework for combating global warming.

This major step forward rewarded the decisive work of French climate diplomacy, embodied by Laurent Fabius, accompanied by a team of outstanding negotiators led by Laurence Tubiana, which enabled COP 21 to reach this crucial agreement that still offered us a chance for a livable world, a world at +1.5°C. Behind this agreement stood a strong promise: that of a sustainable future, a fairer and more breathable world. The Paris Agreement is a new major declaration for the rights of humanity, following the Declaration of the Rights of Man and of the Citizen of 1789 and the Universal Declaration of Human Rights of 1948, all three signed in Paris, the capital of human rights. True to its humanist tradition, Paris continues to inspire and play its full part in the march of the world.

This defining moment was made possible by the unprecedented mobilization and coalition of states, cities, civil society, scientists, activists, trade unions, politicians, and the private sector committed to decarbonization. In other words, the driving forces behind the fight against global warming.

Beyond the states, cities were already at work. As national governments signed the Paris Agreement, I gathered at the Hôtel de Ville in Paris, with the essential support of Michael Bloomberg, former mayor of New York and then UN Special Envoy for Cities and Climate, a thousand mayors from around the world, scientific experts, activists, renowned artists, entrepreneurs, and friends of the climate and the planet. This unprecedented mobilization of local governments, initiated by our city and city networks such as the C40 Cities Climate Leadership Group (C40) and the International Association of Francophone Mayors (AIMF), demonstrated a profound awareness that the climate battle would also be fought in cities. This is one of the key lessons of COP 21: no climate transition can now take place without cities and regions. In other words, we must think globally and act locally, as former UN Secretary-General Boutros Boutros-Ghali so often proclaimed.

We said it then, and we have repeated it ever since, that cities can and must play a major role in the fight against global warming. Quite simply because they are on the front line, where everything is happening, where all global challenges have local consequences, very concretely and very immediately, on human lives. It is up to local elected officials to protect their fellow citizens from the effects of extreme heat, air pollution, drought, flooding, and even fires and mega-fires. Our conviction was that the Paris Agreement should not only be a roadmap for states, but also define the common goal of our local policies to mitigate the consequences of climate change and adapt our living environment. 

We had come a long way. Before the Paris Agreement, mayors, it must be acknowledged, were mere extras in global climate action. For the first time, with COP 21, we got a foot in the door. Since then, we have become recognized, legitimate, and decisive players in the fight against global warming.

Today, cities are clearly the strategic location for climate action. They are both the first to be affected by the effects of global warming and the right scale for climate adaptation and mitigation policies. Why? Let’s not forget that today, more than half of the world’s population lives in cities, i.e. 4 billion people, a figure that will reach 70% by 2050. Growing urbanization makes cities the main emitters of greenhouse gases, responsible for 70% of global emissions, while generating 80% of global GDP. It is at this level that concrete, life-changing actions must be taken, rooted in everyday life, close to residents and ambitious in scope.

Mayors are not waiting for governments to act. When governments back down, they stand firm. I keep in mind the words of United Nations Secretary-General António Guterres: “Cities are where the climate battle will largely be won or lost.”

In Paris, this awareness, which began in 2001 with the measurement of the carbon impact of our actions, enabled us to launch our first Climate Plan in 2007, followed by three others.

In 2014, when I was elected Mayor of Paris, I decided to go even further by firmly committing my city to adapting to global warming and phasing out fossil fuels. Quite simply because pollution kills. We did this by freeing the capital from cars: by giving the riverbanks back to Parisians, by putting an end to urban highways in the heart of Paris, and, more recently, by lowering the speed limit on the ring road to 50 km/h, creating a lane reserved for clean vehicles and carpooling, establishing limited traffic zones in the center of our city, and increasing parking fees for SUVs, as requested by Parisians in a citizen vote.

And the results are clear: in twenty years, car traffic has fallen by 56.2%, leading to a 60% reduction in air pollution, including a 40% reduction in nitrogen dioxide emissions.

We are continuing this commitment by developing active modes of transport, such as walking and cycling. We have created more than 1,565 km of cycle paths. In 2024, for the first time, cycling overtook cars as the most popular mode of transport for everyday journeys.

This has also been accompanied by a massive greening of the streets, with the planting of 170,000 trees between 2020 and 2026, the creation of urban forests, the development of 300 car-free streets around schools, and the creation of oasis courtyards in schools. This is another great success that has been widely welcomed by Parisians. 

And if I did it, it was because I am convinced that these actions save lives. In twenty years, the number of premature deaths due to air pollution has been halved, and the city’s carbon footprint has been reduced by 32%. These changes improve air quality and reduce heat islands: they are all powerful levers for public health. Climate adaptation is a policy for everyday life, for social justice, for better living, here and now.

But we must go further. Because the goal is to phase out fossil fuels. So we are taking action on all fronts: in our buildings, with the aim of renovating all municipal facilities to improve their energy efficiency, and by developing the heating and cooling network. Not to mention food, by offering organic, sustainable, and accessible products in all catering establishments: nurseries, schools, nursing homes, and municipal restaurants. Paris is now the leading public purchaser of organic products in France, and 100% of the meals served in nurseries are sourced from organic farming. This is an exemplary policy and a tool for public health, social justice, and ecological transition.

What we are doing in Paris goes even further: our policy to combat global warming permeates all our actions. We have voted on numerous plans that inform all our policies: the 4^e Climate Plan, the Biodiversity Plan, the Local Bioclimatic Urban Plan, the Resilience Plan and, of course, the Health and Environment Plan. They form a coherent whole that enables us to anticipate, plan and see further ahead. 

It is also in this spirit that we built our bid for the 2024 Olympic and Paralympic Games. The Paris Games were an extraordinary success, but also a real lever for ecological and social transformation. Proof of this is that the Seine has finally been returned to the people of Paris. One hundred years after it was banned, they can swim in it again.

And it is not only Paris that is taking action. The movement launched by the 1,000 mayors who gathered at City Hall in 2015 has continued to grow, organize, and take shape. It led to the launch of the Coalition for High Ambition Multilevel Partnerships for Climate Action (CHAMP) initiative, the result of these multilateral and multilevel dynamics, which are now essential levers for local climate action. This collective work by cities around the world, and the results it has achieved and measured, are now being highlighted at City Hall through the exhibition “From Paris to Belém.” I am thinking, for example, of Copenhagen, which in the 1990s had one of the most polluted ports in Europe. By installing smart retention basins to filter river water before it reaches the port, Copenhagen has been able to create several swimming areas in the city. Innovative policies are everywhere: ultra-low emission zones (ULEZ) in London; the greening and pedestrianization of the canal in Utrecht; the creation of new green spaces including hills and streams in Medellín; in Beijing, the transformation of a steelworks into an ecological park, symbolizing the city’s urban renewal; the redevelopment of Banco Bay in Abidjan; the redevelopment of the banks of the Tiber in Rome; the “Breathe Rio de Janeiro” initiative to reduce air pollution in Rio, and solar-powered street lighting in Nouakchott. The list is long, and all over the world, mayors are working hard and innovating. This is another reason why cities are indispensable and why they are the driving force behind climate action. They are all moving in the same direction.

These concrete actions demonstrate the unique potential of local areas in the fight against global warming. They require unwavering, ongoing commitment and great determination. I can testify to this, as can many of my colleagues. We mayors are constantly confronted with unprecedented violence: powerful and organized lobbies, constant attempts to discredit us, caricature us, and orchestrated campaigns to make us back down. This is a recurring pattern, because we are often the first to oppose fossil fuel interests, as we did in Paris when we signed the treaty on the non-proliferation of fossil fuels.

Faced with this constant, organized, and aggressive pressure, cities must also turn to the courts to defend their environmental policies. This was the case in May 2018, when my friends, the mayor of Brussels, Philippe Close, and the former mayor of Madrid, Manuela Carmena, and I took legal action in the European courts following the “dieselgate” scandal, which granted car manufacturers a veritable “license to pollute.” And we won. This victory proved that cities can make their voices heard in the face of industrial powers, in the name of public health. 

There are many other obstacles. The past decade has been marked by considerable opposition to those who wanted to take action, notably with the US withdrawal from the Paris Agreement. However, US cities have continued to fight. We are also facing the rise of climate skepticism, climate revisionism, and mistrust of science, which runs counter to all rational considerations, as well as all forms of populism that profit from and feed on this mistrust. or the proliferation of disinformation campaigns amplified by social media, all of which have been challenges that we have had to address directly. And we have done so with ever greater force. One of the peaceful weapons we have deployed is the “15-minute city,” which enables citizens to get involved in their local communities and become agents of change for themselves, their children, and their grandchildren. In other words, for the rights of future generations.

Despite the headwinds, we must stand firm. The climate emergency is not a distant threat: it is here. The figures are clear, and scientists have been warning us for years. 2024 was the hottest year on record, with an average temperature 1.6°C above pre-industrial levels. It was also marked by a dramatic acceleration of extreme weather events: melting ice and rising sea levels, Cyclone Chido in Mayotte last December, deadly floods in Valencia in the fall, devastating fires in Los Angeles in January, and most recently, the floods in Texas. The year 2025 is also likely to break all records. These are not scientific abstractions, they are everyday reality and, sadly, the future of humanity.

So, of course, we must celebrate the tenth anniversary of the Paris Agreement. But today, at the global level, we could reach a global temperature rise of +3°C by 2100. Without COP21, it must be said, it would have been worse. 

To stand firm and achieve these goals, mayors have organized themselves alongside international organizations and willing states. This momentum has given rise to a new, multi-level multilateralism that is now essential for tackling the major global challenges ahead. This has been achieved through international networks of cities, such as C40, which now has 97 member cities among the largest in the world; AIMF; the Global Covenant of Mayors (GCoM), which brings together more than 12,000 mayors representing more than one billion citizens, or about 15% of the world’s population; and the OECD’s Mayors for Inclusive Growth initiative. These are the spearheads of this climate alliance. Between 2015 and 2023, average per capita emissions fell by 6.3% in C40 cities, while those of their national governments remained stable. None of this would have been possible without COP 21.

That is why mayors have been campaigning for greater recognition of the role of local governments in global climate governance. At COP 28 in Dubai in 2023, mayors were included in the official conference agenda for the first time, with the Local Climate Action Summit. This is obviously a positive sign, but much more needs to be done. This is the whole point of CHAMP, an ambitious advocacy initiative aimed at integrating local contributions into nationally determined contributions (NDCs) and, at the same time, facilitating direct financing for cities for the ecological transition, commensurate with their actions. The Pact for the Future, adopted by the United Nations General Assembly in 2024, also significantly strengthens the place of cities in international negotiations. 

Despite these undeniable successes and the place that cities have been recognized as having since COP21, it must be said clearly: they remain marginalized in international climate governance and financing. While global climate finance currently stands at $1.9 trillion per year, cities receive less than 10%.

Mayors need direct access to finance now more than ever to fully assume their responsibilities and go further.

This context gives particular resonance to the next COP 30, to be held in Belém, Brazil, in 2025, under the presidency of Luiz Inácio Lula da Silva. This conference could well be our last chance. It must mark a decisive turning point towards more inclusive climate governance under the auspices of the United Nations. COP 30 will be as important as COP 21. 

Belém, in the heart of the Amazon, will champion the essential alliance between climate and biodiversity. This COP will also see a decisive strengthening of financial and political commitments to cities, as well as a reconsideration and respect for the global South by the North, an intensified fight against disinformation, and the consolidation of global climate justice.

The Belém COP will be the COP of cities, the COP of hope. I will never tire of repeating this. Nothing will happen without them. Because they are the democratic level par excellence, the one that best represents the citizens, territories, and human communities of our entire planet.

Finally, to renew our climate ambitions in these difficult times for the climate and for democracy, it is essential that the planets align once again. All the humanist forces must come together, as they did in Paris ten years ago. With cities alongside states. 

Ten years after Paris, let us ensure that Belém is the birthplace of a new agreement for the climate and for humanity. May it give us the strength to face the challenges of the present with hope. We owe it to those who are alive today. We owe it to future generations.

I believe in this deeply and I am fully committed to it.