Around the world, well-funded, organised climate deniers are spreading lies about the crisis. We call on governments and tech companies to step up

• Sadiq Khan is mayor of London and Anne Hidalgo is mayor of Paris

As mayors of two of the world’s great cities, we see every day how the climate emergency is already reshaping people’s lives, affecting the people and places we love. From deadly heatwaves and devastating floods to rising inequality and health crises driven by air pollution, the costs of inaction are not theoretical; they are measured in lives taken, homes destroyed and business revenue lost.

Ten years ago, the Paris agreement was signed, marking a turning point in the global fight against climate breakdown. But today, progress is being undermined by a deeply concerning threat: a surge in climate deniers and delayers spreading virulent disinformation. We mustn’t let this hope disappear as the world gathers in Belém at the end of 2025 for Cop30.

Sadiq Khan is mayor of London and co-chair of C40 Cities. Anne Hidalgo is mayor of Paris, global ambassador for the Global Covenant of Mayors and vice-chair of C40 Cities

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