The event, which includes a discussion on modern slavery, will draw an international collection of government officials and
"This unprecedented gathering of global leaders is a wake-up call to face up to the common threats of climate change and human exploitation," Brown said in a statement Thursday. "This is about the future of humanity and how we as human beings live and treat one another and the natural world around us."
Brown, who once considered a life in the priesthood and spent years in a Jesuit seminary before dropping out, has traveled widely to urge stronger action against the advance of global warming. He spoke at a conference here on Wednesday and told reporters that he wanted to "light a fire" under national leaders.
In an interview this week, Brown said Francis, who urged in a recent encyclical that more effort was needed to fight global warming, was "bringing a moral and theological dimension that adds to the market and political calculations" about climate change.
"We face an existential threat to human existence as we know it," he said. "It's not being taken seriously by the vast majority of powerful people. When the pope, as a powerful person, issues this encyclical, it's a helpful addition to the mix."
The pope has expressed concern, however, over cap and trade, a system used in California, Europe and elsewhere to cap polluting emissions by forcing businesses to buy and trade permits for releasing carbon into the atmosphere.
"In no way does it allow for the radical change which present circumstances require," Francis wrote. "Rather, it may simply become a ploy which permits maintaining the excessive consumption of some countries and sectors."
Brown said that the program, created under his predecessor, Republican Gov. Arnold Schwarzenegger, is part of California's successful strategy to combat climate change.
The governor also is promoting legislation, currently pending in the Assembly, that would reduce the use of gasoline, increase energy efficiency and require more electricity from renewable sources.