Cities are central to our fight against climate change. They are responsible for more than 70% of all carbon emissions and at high risk from the climate impacts these emissions are causing, with floods, hurricanes and heatwaves causing devastation worldwide. More than 11,600 cities globally with a billion people have already recognised the need to take action and joined the Global Covenant of Mayors, the largest alliance for city climate leadership. A growing number have set ambitious net zero targets.

But the wholesale decarbonisation of a city is something that has never been done before and the challenge is absolutely enormous. There's no lack of ideas - cities are swamped with initiatives, proposals and reports - but it is increasingly difficult to see how they are linked and what the consequences might be - to get the whole picture.