An anonymous reader quotes a report from The Guardian: Mayors of more than 7,400 cities across the world have vowed that Donald Trump's decision to withdraw from the Paris accord will spur greater local efforts to combat climate change. At the first meeting of a "global covenant of mayors," city leaders from across the US, Europe and elsewhere pledged to work together to keep to the commitments made by Barack Obama two years ago. Cities will devise a standard measurement of emission reductions to help them monitor their progress. They will also share ideas for delivering carbon-free transport and housing. Kassim Reed, the mayor of Atlanta, told reporters he had travelled to Europe to "send a signal" that US states and cities would execute the policies Obama committed to, whether the current White House occupants agreed or not. Reed, whose administration has promised that the city of Atlanta will use 100% renewable energy by 2035, said 75% of the US population and GDP lay in urban areas, where local leaders were committed to fighting climate change. "We have the ability to still achieve between 35% and 45% CO2 emission reductions without the involvement of the national government and it is why I chose to be here at this time to send a signal to 7,400 cities around the world that now should be a time of optimism, passion and action," he said.