California Governor Jerry Brown speaks on climate at Vatican

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.

The Sacramento Bee reports Tuesday that Brown addressed mayors and other government officials from around the world, issuing criticism of Republican politicians and business interests skeptical of climate change.

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.