SAN FRANCISCO (CBS/AP) — At a climate summit at the Vatican, Gov. Jerry Brown said the world may have reached a tipping point on global warming and that humanity must reverse course or face extinction.

Brown addressed mayors and other government officials from around the world, issuing criticism of Republican politicians and business interests skeptical of climate change.

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Vatican Climate Summit. (GABRIEL BOUYS/AFP/Getty Images)

Vatican Climate Summit.

“We have very powerful opposition that, in at least my country, spends billions on trying to keep from office people such as yourselves and elect troglodytes and other deniers of the obvious science,” Brown told the conference according to the Los Angeles Times.

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Brown is at the Vatican amid stepped up efforts to bring support for policies to reduce greenhouse gas emissions. The summit was called by Pope Francis following the recent release of his encyclical on climate change.

Brown has made climate change a central theme of his governorship, promoting a plan to set a carbon reduction benchmark in North America. The plan would increase statewide renewable electricity use to 50 percent and have drivers use half as much gasoline, among other changes.

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