VATICAN CITY — The governor of California is denouncing global warming deniers who are "bamboozling" the public with propaganda and putting "troglodytes" into office rather than environmentally responsible leaders.

Gov. Jerry Brown was one of the keynote speakers Tuesday at a conference of eco-friendly mayors at the Vatican. California has enacted the toughest greenhouse gas emissions standards in North America.

To rousing applause, Brown denounced the "fierce opposition and blind inertia" in the U.S. by climate skeptics who he says are seeking to "falsify the scientific record" and convince politicians, scientists and the general public that global warming isn't happening.

Brown, a former Jesuit seminarian, urged the mayors to not be complacent in opposing them. He said climate deniers are spending "billions on trying to keep from office people such as yourselves and elect troglodytes and other deniers of the obvious science."

The mayors are expected to sign a Vatican declaration urging world leaders to take bold action at Paris climate talks this December.

Environmentally friendly mayors from around the world are gathering at the Vatican for a two-day conference rallying momentum ahead of Paris climate negotiations later this year.

Pope Francis is expected to address the meeting later Tuesday. He's a new hero to the environmental movement, thanks to his recent encyclical denouncing the world's fossil fuel-based economy that he says exploits the poor and destroys the Earth.

The mayors are expected to sign a declaration at the end of the day demanding that their national leaders approve a "bold climate agreement" at Paris talks in December that keeps global warming at a safe limit for humanity.