The latest in the Vatican's meeting of mayors on fighting climate change and human trafficking. All times local.

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11:00 a.m.

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.