Brown was speaking in Beijing where he is hoping to drum up Chinese support for his state's aggressive efforts.
Brown was speaking in Beijing where he is hoping to drum up Chinese support for his state's aggressive efforts to curb emissions in the wake of President Donald Trump's decision to pull the United States out of the Paris Accord.
"There are still some in powerful places who are resisting reality, who are resisting the obvious science that we know governs our lives," Brown said during a speech on the sidelines of a ministerial-level clean energy meeting.
Brown is making several public appearances in the Chinese capital as part of a week-long trip to the country.
His full-throated call to action on the environment contrasted sharply with the low-key presence of US Secretary of Energy Rick Perry, who used his appearance at the conference to talk up the benefits of carbon capture, utilisation and storage (CCUS) in future energy production.
"Our experience with CCUS proves that you can do the right thing for the environment and the economy too," Perry said, adding that he looked "forward to international collaboration between US and Canada, and with other countries”.
The US retreat from the Paris deal struck in 2015 is seen as giving China, the world's biggest polluter, a chance to snatch the lead in the global battle against climate change.
Beijing has said it will stick with the agreement despite the US withdrawal.
During his week-long tour of China, Brown plans to sign agreements focused on clean energy and technology cooperation with local governments.
His itinerary included a meeting with President Xi Jinping on Tuesday to discuss cooperation on green development.
"The world is not doing enough," Brown said.
"We’re on the road to a very negative and disastrous future unless we increase the tempo of change," he added, comparing the fight to efforts to defeat fascism during World War II.
"The threat of climate is not of the same nature as the fascist forces that were threatening the world, but in some ways it may even be more devastating."
California, which has the world's sixth-largest economy, is one of a handful of American states that have pledged to continue fighting climate change regardless of action at the federal level.
The state -- which has some of the worst air pollution in the country -- has dramatically slashed its climate-warming emissions in the last decade.
It has pledged to cut greenhouse gas emissions to 1990 levels by 2020, and to 40 percent below 1990 levels by 2030.
Before setting off for China, Brown pledged California would resist Trump's decision to abandon the Paris deal, describing the move as "misguided and insane".