In June 2025, in London, representatives from the world’s smartest cities convened at a Cities Climate Action Summit as part of London Climate Action Week 2025.
The meetings provided the opportunity for policymakers, technologists, and financiers to learn what is working and what is not working in cities ahead of the United Nations Climate Change Conference, COP 30, being held in Brazil from 10 November to 21 November 2025.
The London event is one of a number of meetings that are helping to drive change in cities as they battle against the effects of climate change. And make no mistake, it is cities that are on the front line. By 2050, it is projected that 68% of the world’s population will live in urban areas, a demographic development that has implications for public policymaking, resilience planning, technology adoption, and financial backing.
Cities on the agenda
The event featured discussions on scaling up climate action at the local level and city governance in relation to climate change, notably around the ideas of adaptation and resilience. As the impacts of climate change become more pronounced, cities and local governments have become critical players in the global effort to reduce emissions, build resilience, and deliver sustainable development. Emma Howard Boyd, Chair of the London Climate Resilience Review, discussed how climate action can drive innovation, encourage citizen engagement, and tailor solutions to the specific needs of communities.
The event also heard from Lord Marvin Rees, the former Mayor of Bristol City Council, who discussed the local challenges around meeting net zero targets. The UK has pledged to reach net zero carbon emissions by 2050, and all of the UK’s largest 50 cities have set their own net-zero targets.
The problem was that, during his tenure as Bristol Mayor and Chair of the UK’s Core Cities Group, Rees realised that there was no central government plan to make this happen. He decided to take matters into his own hands and, with others, set up the Cities Climate Investment Commission, 3Ci. He also oversaw the launch of Bristol City Leap, a new approach towards decarbonisation at the city scale. The result is a twenty-year joint venture partnership between Bristol City Council, Ameresco, and Vattenfall Heat UK, which will enable the delivery of GBP1 billion of investment into Bristol’s energy system.
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One of the most familiar sights in cities of the future will be electric vehicles (EVs), and the event featured a panel discussion featuring deputy mayors and transport leads from cities across Europe and North America, showcasing how public-private partnerships can drive clean air, green jobs, and more accessible urban mobility. The panel included Rebecca Tinucci, the global head of sustainability at Uber, and discussed a partnership between C40 Cities and Uber to accelerate the rollout of electric vehicle charging infrastructure in three cities: Phoenix, Boston, and London. The program will support high-mileage commercial drivers, such as ride-hailing, taxi, and freight workers, by using new data-driven tools to plan equitable, high-use charging networks.
One of the key technologies already used by cities worldwide is digital twins, which provide a digital representation or model of a physical thing. The technology provides a virtual model that can be used to run simulations, identify patterns, and interact with real-world objects. As well as all of the digital twins now being used by most cities to respond to climate change is one from Nvidia. Its Earth-2 climate digital twin cloud platform uses AI, GPU acceleration, physical simulations, and computer graphics to develop applications intended to simulate and visualise weather and climate predictions with greater speed and accuracy.
Nvidia has coined the idea of cBottle—dubbed “Climate in a Bottle”—the world’s first generative AI foundation model designed to simulate global climate at kilometer resolution. The model, part of the Nvidia Earth-2 platform, can generate realistic atmospheric states that can be conditioned on inputs like the time of day, day of the year, and sea surface temperatures. Nvidia argues it offers a new way to understand and anticipate Earth’s most complex natural systems.
How cities are delivering urgent and ambitious climate action will be showcased at the C40 World Mayors Summit in Rio de Janeiro from November 3-5, just days before the wider COP climate negotiations take place, not in Rio, but at Belém, a port city located 1500 miles away that provides a gateway to the Amazon River.
