The mayors of more than 7,400 cities around the world have vowed that Donald Trump's decision to withdraw the United States from the Paris climate deal will spur greater local efforts to combat climate change. In the United States itself, authorities in 12 states as well as cities, towns, businesses and universities nationwide are all keen to show their support for the Paris agreement. But what exactly can they do? Our US correspondent reports from Pennsylvania.
A programme prepared by Patrick Lovett and Aline Schmidt.