From Sierra Leone to Milan, cities are introducing their own rules and innovations in the face of rising temperatures

Wooden stakes bearing pictures of young men were driven into the yellow sands of Copacabana beach this week, opposite Rio de Janeiro’s swanky hotels on Avenida Atlântica where 300 mayors and their entourages were staying during the C40 World Mayors Summit.

Smiling up at the mayors in their hotel suites were photographs of four officers killed in what was the deadliest police raid in Brazilian history, just a few days before the summit. A further 117 people were killed in the operation in two of Rio’s largest clusters of favelas – the Complexo do Alemão and the Complexo da Penha – in what the police said was a clampdown on organised crime.

Sadiq Khan, the city’s first Muslim mayor, says: ‘We are united by something far more fundamental, our belief in the power of politics to change people’s lives for the better’

While the soon-to-be first Muslim mayor of New York, Zohran Mamdani, was in the final throes of his mayoral campaign on a brisk day in New York, Sadiq Khan, the first Muslim of mayor of London, was wrapping up a two-day climate summit in a steamy if overcast Rio de Janeiro.

“Hope is not gone,” Khan told the 300 city mayors gathered in the Brazilian city’s museum of modern art.