Khan has joined the globalist C40 Climate Leadership group which comprises, in its own words, "a network of nearly 100 mayors of the world's leading cities that are united in action to confront the climate crisis", and has commissioned a report making demands for cities to slash their greenhouse gas emissions by 2030.

Khan, who chairs the C40 group, has received backlash from Londoners following this month's Ulez (ultra low emissions zone) expansion. Though the C40 Cities initiative, under the guise of the Clean Air Wins campaign, has shared videos in favour of Ulez, the Wall Street Journal this week highlighted the less highly-publicized proposals in its report, authored in collaboration with the University of Leeds, such as "no meat, no dairy and no private vehicles".