Pope Francis on Tuesday called on world leaders to take "a very strong stand" on climate change at a U.N. summit this year in Paris.
The pope spoke at a Vatican conference attended by dozens of mayors and governors from major world jurisdictions, who signed a joint declaration demanding action on human-induced global warming. The document states the Paris summit in December "may be the last effective opportunity" for world leaders to negotiate meaningful environmental policy.
"I have great hopes for the Paris summit," Francis said. "I have great hopes that a fundamental agreement is reached."
In unprepared remarks Tuesday, the pope told his audience that he also hoped the summit would address links between climate change and human trafficking. Conference documents linked the two phenomena, saying that global warming is a key contributor to "poverty and forced migration" in the developing world.
The Vatican conference, attended by 60 government officials from the United States, Europe, South America, Africa and Asia, came just weeks after the pontiff issued the first papal encyclical dedicated to environmental concerns.
In that strongly worded landmark letter, Francis said global warming was pushing the Earth toward environmental ruin. He also said human activity linked to climate change could lead to "an unprecedented destruction of ecosystems" in this century.
He also called for massive and immediate political and economic transformation in the developed world, saying it was needed to curb global dependence on highly polluting fossil fuels linked to global warming.
President Barack Obama, speaking in June, welcomed the papal initiatives, saying they "make the case [for environmental action], clearly and powerfully and with the clear moral authority of [the pope's] position."
Climate change skeptics, including some U.S. Republican presidential candidates, have dismissed the pope's environmental messages. Candidate Jeb Bush, a convert to Roman Catholicism, said in June: "I don't get economic policy from my bishops or my cardinal or my pope."
Many U.S. conservatives say they do not believe human activity is the cause of global warming. They point to natural fluctuations in global temperatures as the primary cause of rising temperatures.