In an interview before his trip, the governor said the world needs to make significant changes in order to prevent an irreversible "tipping point" in the environment, and he compared the situation to the sinking of the Titanic.
"The music was playing. They were all in their finest clothing. But the damn thing went down," he said. "We're talking about something like that for the whole human experiment."
Brown said the threats from climate change are grave and numerous: "Migration, hunger, war, a major assault on civilization as we know it. The stakes couldn't be higher, even though they're not immediate."
The governor is one of the featured speakers at the conference, along with former Vice President Al Gore and former Mexican President Felipe Calderón.
Before his speech Wednesday, Brown is scheduled to hold a news conference with Ontario Premier Kathleen Wynne and Quebec Premier Philippe Couillard. The governor has been trying to rally more states and provinces to agree to stricter standards for reducing greenhouse gas emissions.
"What we're seeking is to increase the number of states and provinces that join with California in committing themselves to serious and significant climate reductions," Brown said. "That's the purpose of the meeting."
With some countries slow to take action on a national level, Brown is pushing a "bottom up" approach to addressing climate change, in which individual states and provinces set their own targets in hopes of spurring broader action. World leaders plan to meet in Paris this year to develop a new environmental accord.
"I'm going to do whatever I can. You can say, well, is that enough?" he said. "Nothing is enough. But doing nothing is not an option."