Pope Francis released a highly anticipated papal document on climate change and the environment on Thursday, calling the fight against global warming a moral imperative and "one of the principal challenges facing humanity."
In the 180-page letter, which carries enormous weight within the Catholic community and marks a significant milestone in the global climate change debate, Francis warns that human activity is largely responsible for "global environmental deterioration" and that humans must fundamentally change their consumption patterns.
The encyclical is already resonating in American politics.
Social conservatives in the Republican Party have long been aligned with the Catholic Church on controversial issues such as same-sex marriage, abortion, euthanasia and embryonic stem cell research. But since assuming the papacy in 2013, Francis has adopted a notably progressive tone, drawing a contrast between himself and his predecessor, Pope Benedict XVI. He's cautioned that the church has become "obsessed" with issues such as abortion, same-sex marriage and contraception and has appealed to Catholic leaders to focus on preaching inclusion and love.
Now, his official exploration of climate change presents a new and delicate dilemma for some Catholic Republican politicians, including several candidates seeking the GOP nomination for president in 2016.
Their challenge is to navigate the tension between the church's aggressive stance on climate, with a powerful slice of the party's base -- including the fossil fuel industry -- that balks at sweeping environmental regulations.
"Having the Pope weigh in on this topic will help the debate transcend some of the partisan divide that it's caught in now," Miami Archbishop Thomas Wenski told CNN.
Wenski, who chairs the committee on domestic justice and human development at the U.S. Conference of Bishops, said he'll be paying close attention to how the 2016 GOP presidential candidates respond to the pope's message.
"I'm going to look for how they're going to react in the next couple of weeks," he said.
Some Republican candidates have deeply resisted the notion of climate change.
"The satellite data demonstrate that there has been no significant warming whatsoever for 17 years," Texas Sen. Ted Cruz said earlier this year.
Former South Carolina Rep. Bob Inglis, a Republican environmentalist who lost re-election in a primary to Rep. Trey Gowdy in 2010, said the papal document will force global warming skeptics and critics of environmental regulations in the GOP to do some soul-searching.
"There's a lot of Republicans who may have in the past been critical of fellow Catholics who they call 'cafeteria Catholics' who don't follow the church's teachings -- say, on abortion," said Inglis, an Episcopalian. "But now, are they going to become 'cafeteria Catholics' themselves and not follow the church's teachings on climate change?"
The Pope's entry into the U.S. debate on climate change will come in two stages: first the release of his encyclical this week, and then a speech before a joint session of Congress in September.
On the 2016 campaign trail, Republican candidates have started fielding questions about the Pope's climate message. Former Florida Gov. Jeb Bush, a Catholic, questioned whether Pope Francis was qualified to address such a divisive political issue.
"I don't get economic policies from my bishops or my cardinals or my Pope," Bush said at a town hall in New Hampshire this week. "I think religion ought to be about making us better as people and less about things that end up getting into the political realm."
Others White House aspirants are treading carefully.
"The last person on Earth I want to try to argue with will be the Pope," former Arkansas Gov. Mike Huckabee, a Southern Baptist preacher, told CNN in South Carolina.
Ohio Gov. John Kasich, who has yet to officially launch a White House bid, said in an interview that while humans have an "obligation" to take care of the environment, he's wary of any kind of "extremism" that translates to "worshiping the environment." (Kasich was raised Catholic and later became
Like Bush, some of his fellow Catholic candidates in the GOP field, such as Florida Sen. Marco Rubio and New Jersey Gov. Chris Christie, have in the past expressed skepticism about the extent to which human activity contributes to global warming.
Many Republicans have an interest in appeasing the deep-pocketed energy industry.
The oil and gas industry contributed $52 million to Republican candidates and committees in the 2012 cycle, compared with around $6.5 million to Democratic candidates and committee, according to data from the Center for Responsive Politics
(these figures do not include contributions to groups that don't disclose their donors).
The Pope's encyclical pointed to the "intensive use of fossil fuels" as one of the core causes of global warming.
But Republicans also face the political reality that climate change is an important electoral issue. National polls show that swing voters including independents, millennials and Hispanics tend to be more alarmed about global warming than the more traditional GOP base.
Environmental advocates hope GOP elected officials who view global warming as a serious problem but fear the political ramifications of advocating for climate action will seek refuge in the Pope.
"The Pope is the leader of the church, and he's taking this issue as seriously as he can," said John Coequyt, director of federal and international climate campaigns at the Sierra Club. "This provides a huge opening for a number of politicians to change their position."
Others are more skeptical.
Maine Sen. Susan Collins, who recently hosted Catholic bishops on Capitol Hill last month to discuss Francis' encyclical, told CNN this week that it seems unlikely that the document will sway her fellow GOP colleagues who do not view global warming as a serious problem.
In fact, surveys show that Catholic Republicans tend to be far less concerned about global warming than their Democratic counterparts.
Just 24% of Catholic Republicans believe that the Earth's warming is caused by human activity and that it is a "very serious problem," compared with more than six in 10 Catholic Democrats who hold these views, according to a new Pew Research Center poll
out this week.
Democratic Sen. Sheldon Whitehouse of Rhode Island, who co-hosted the Catholic bishops with Collins, said the "moral dimension" of the Pope's argument should not be underestimated.
"Every Catholic school, every Catholic parish, every Catholic university, all the Catholic societies -- they take on the responsibility to propagate the encyclical and make sure that people are aware of it," Whitehouse said. "It's going to be huge."