By C40 Cities Co-Chairs Yvonne Aki-Sawyerr, Mayor of Freetown and Sadiq Khan, Mayor of London

Dear Heads of State,

We are writing to you with an inescapable truth. The era of fossil fuels is coming to an end. 

As co-chairs of C40 Cities, we bring together nearly 100 of the world’s greatest cities to act together to take courageous steps to reduce fossil fuel use across energy, buildings and transport in line with our goal to halve global emissions across our network by 2030.  We are working with our partners in the private sector, trade unions, civil society and at the state and regional level to drive investment to deliver a just transition that includes fossil fuel workers.

But to fully meet the challenge and urgency of the climate crisis, we need three key things from you as you gather at COP28: to curb the undue influence of the fossil fuel industry, to move public money from fossil fuels to a just and clean energy transition and partner with us to accelerate action and prosperity.

We are in a moment of peril. Scientists, youth and communities are sounding the alarm. The world is teetering on the brink of exceeding the 1.5°C guardrail, after which climate systems don’t just heat up but drastically break down, threatening economies and livelihoods everywhere, causing loss, damage and conflict. These challenges will even further stretch the ability of countries, regions and cities to respond. 

Fossil fuels are responsible for the overwhelming majority of the world’s carbon emissions and most pollutants in our air. Fatal flooding, record-breaking heat waves, deadly wildfires, toxic air quality and water scarcity are already threatening millions of our residents. Across the world, people are struggling to access or afford energy while fossil fuel companies report record profits.  Communities most affected are usually the least responsible for fossil fuel use. We must phase out fossil fuels to protect our climate but also to protect people from the unjust impacts on their health and standard of living.

Crucially, we must not be lured into false solutions. There is no viable technology currently available or expected to be in the near future that can extract carbon created by fossil fuels at the scale, pace and cost we need.

That is why the world must deliver, at the minimum, the calls of the International Energy Agency to halve global fossil fuel use by 2035 and stop any further investment in new fossil fuel projects. The global goals of tripling renewable energy and doubling energy efficiency by 2030 are essential to provide energy security and boost sustainable development. The most developed and historically responsible countries must act faster, in line with the UN Secretary General’s Acceleration Agenda.

This is also a moment to acknowledge progress. For emerging economies expanding energy access, renewables are the cheapest power source in most parts of the world. They require no fuel to run. Unlike fossil fuels, therefore, they do not create volatile price hikes that add huge costs to people’s energy bills while creating record profits for fossil fuel companies. Moreover, renewable energy has provided employment to millions around the world in the last 10 years.  

There is significant potential for us as local leaders to accelerate the end of fossil fuels and opportunities for everyone in the new green economy. C40 cities represent more than 700 million people and 25% of the global economy and are demonstrating the scale and pace of this progress first-hand.

Mayors are already improving the energy efficiency of homes, schools, offices, expanding and electrifying bus fleets worldwide while lowering energy bills, improving people’s health, and driving the creation of good green jobs. We are doing our part to move money away from fossil fuels by divesting from polluting sources, working towards cities that are powered by 100% renewable energy by 2035, developing skills academies that reach under-served groups and establishing funds for affected workers.  

Together, we are sending clear signals that the future of our cities will be clean and just. But without further and collective action from national governments to overcome key barriers, progress will not move fast enough.

The first is simple – curb the undue influence of the fossil fuel industry in compromising the future of humanity.

The second is to move the money currently used to subsidise fossil fuels to accelerate a just clean energy transition. Last year, fossil fuels subsidies in G20 countries reached an alarming US$1.4 trillion. The financial benefits of these subsidies are deeply unjust. In low and middle-income countries, the poorest receive only 7% of this benefit, while the already rich receive 43%. Action must be taken to reverse this situation so that at least 40% of public climate investments go to low-income communities, deprived neighbourhoods and those affected by the energy transition. ‘Just transition’ is too often an empty phrase. Vital support could make it a reality by ensuring the workforce has targeted support, training and a real voice in the transition.

The final action is our offer to you: work with us.

We cannot end the era of fossil fuels without working together. We need partnerships across all levels of government, the economy and society to accelerate collective progress, building strong climate and investment plans to end the injustices caused by continued fossil fuel use. The solutions are proven. Together, we can raise global ambition and accelerate a fair and fast transition.


Yvonne Aki-Sawyerr, Mayor of Freetown and C40 Cities Co-Chair

Sadiq Khan, Mayor of London and C40 Cities Co-Chair

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