Gov. Jerry Brown of California on Thursday reinforced his reputation as America’s de facto leader on climate change, announcing to cheering crowds in Hamburg, Germany that his state would gather leaders from around the world for a global warming summit next year.

Speaking by videoconference to the Global Citizens Festival in Hamburg, where President Donald Trump is joining other world leaders for the Group of 20 economic summit, Governor Brown said the president “doesn’t speak for the rest of America” in pulling out of the Paris agreement on climate change.

“Look, it’s up to you and it’s up to me and tens of millions of other people to get it together to roll back the forces of carbonization and join together to combat the existential threat of climate change. That is why we’re having the Climate Action Summit in San Francisco, September 2018,” Governor Brown told the crowd.