Al Gore and Jerry Brown on America’s Renewable Future

Cities and states around the U.S. are vowing to fight climate change, using President Trump’s decision to leave the Paris accords to galvanize their movement. Many climate policy experts say there is promise in a bottom-up approach, with sub-national governments leading charges to reduce greenhouse gas emissions and spur innovation in clean energy regardless of what might be materializing on the national stage.

Dozens of American cities have pledged to use 100% renewable energy by 2050 or earlier. But the most ambitious goal may be coming from California. Lawmakers in the state, which is home to one in eight Americans, are considering legislation that would require all of the state’s power to come from sources such as wind and solar by 2045. “It’s about the world,” California Gov. Jerry Brown said at a recent signing ceremony for another climate bill, “and California is leading that world in dealing with a principal existential threat humanity faces.”

TIME spoke with Brown, as well as environmental crusader Al Gore, about what’s happening in energy now and how it might shape America’s future.