In 2005, countries around the world ratified the Kyoto Protocol. It was the first big, legally-binding international climate policy, but there was a big drawback: The United States, the world’s richest country and second-highest emitter, didn’t ratify it.In response, American mayors took action. Even if the US wouldn’t commit to cutting climate emissions, their cities would. It was the classic “think global, act local” move.It started with mayoral resolutions—a bunch of “whereases” laying out the reasons cities needed their own climate targets. Whereas manmade climate change is happening. Whereas cities are responsible for 70% of the world’s emissions. Whereas more than half the world’s people live in cities. Whereas cities are most vulnerable to the effects of climate change.Therefore? Our city is going to do something about it. Mayors proclaimed, city councils adopted, and gavels cracked on podiums across the country as city climate plans were created, along with a new job to manage it all: the chief sustainability officer.Twenty years later, hundreds of US cities have climate plans. Their chief sustainability officers are responsible for aggressive decarbonization goals that require deep cuts to emissions, and fast. But are cities actually meeting their targets? And do city sustainability officers have what they need to meet them?Read the rest of this story at sciencefriday.com.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.