"The world's governments alone cannot make the progress that is needed on global climate change," Schwarzenegger said at the 192-nation conference. "They need the cities, the states, the provinces, the regions. They need the corporations, the activists, the scientists, the universities."
Since becoming California governor in 2003, Schwarzenegger has made combating climate change one of his top priorities. California is on track to reduce greenhouse gas emissions to 1990 levels by 2020, about a 30 percent cut from projected emissions. The statewide mandate was the first in the United States.
Schwarzenegger, a Republican, called critics of climate change out of touch with reality.
"There are people who just don't believe about working on the environment," he said. "They don't believe there is such a thing as global warming. They're still living in the Stone Age, which is OK. We need people like that too."
Obama and more than 100 other national leaders are heading to Copenhagen later this week in hopes of forging the framework of a plan to limit the causes of climate change.
ABC News' Kristina Wong and The Associated Press contributed to this report.