Pope Francis’ scheduled address to a joint session of Congress this fall could put Republican lawmakers who reject a human role in global warming in the hot seat.

The timing of his appearance suggests the pontiff might have global warming on his mind.

Francis’ Sept. 24 visit to Capitol Hill will be bookended by the expected release this spring of an encyclical, or papal letter, on global warming and the high-stakes U.N. climate talks in Paris at year’s end.

John Carr, the director of Georgetown University’s Initiative on Catholic Social Thought and Public Life, said the pope’s visit could be a bipartisan case of “careful what you wish for.”

Catholic Republicans like House Speaker John Boehner of Ohio, Rep. Paul Ryan of Wisconsin and Sen. Marco Rubio of Florida will hear from a pontiff who has spoken out in recent months about the human role in driving global warming – a link the lawmakers don’t accept. He’s also likely to remind liberal Catholics like House Minority Leader Nancy Pelosi (D-Calif.) that their stances on abortion and gay marriage aren’t in line with church teaching.

“Everybody will feel uncomfortable at points of the speech, and everybody is going to be challenged in some way,” Carr said.

Liberals hope Francis will make an impassioned plea for climate action along with arguments against income inequality, the dangers of unfettered capitalism and Catholics’ becoming “obsessed” with abortion and homosexuality – positions that have chipped away at the alignment between American conservatives and the Vatican under John Paul II and Benedict XVI.

Francis hasn’t been shy about speaking out on global warming and environmental concerns. He did, after all, take the name Francis upon his 2013 election as pope, for Francis of Assisi, a 13th-century friar considered the patron saint of ecology.

“I don’t know if it is all [man-made], but the majority is,” he said in an interview last month. “For the most part, it is man who continuously slaps down nature.”

And in a homily last week at his Vatican City residence, Francis called on Christians to “protect creation.”

“When we hear that people have meetings about how to preserve creation, we can say: ‘No, they are the greens!’ No, they are not the greens! This is the Christian [duty]! This is our response to the first creation of God. And our responsibility,” the pope said, according to Vatican Radio. “A Christian who does not protect creation, who does not let it grow, is a Christian who does not care about the work of God, that work that was born from the love of God for us.”

And last week, a Vatican spokesman said cardinals were discussing in closed-door meetings the possible launch of an environmental think tank. “We see a growth in the awareness [of environmental problems] and in the importance of reflection, commitment and study of environmental issues and their relation to social and human questions,” the Rev. Federico Lombardi told reporters, according to Reuters.

Some see a political edge to the pope’s views on nature.

“I don’t want to call anybody out, but it just seems like there needs to be a greater understanding of the science of climate change and then, more importantly, how do we move beyond that to figure out what do we need to do,” said Dan Misleh of Catholic Climate Covenant.

But conservative Catholics say climate change will never rise to the level of doctrinal importance reserved for issues like abortion and homosexuality – on which the Vatican takes a hard and fast position to which all Catholics are expected to adhere. They say Republicans who disagree with Francis’ saying warming is “mostly” the result of industrial greenhouse gas emissions cannot be seen to be as much in error as pro-abortion-rights Catholic Democrats.

“Abortion is very clear-cut. It’s regarded as an intrinsic evil,” said Bill Donohue of the conservative Catholic League, who once sent Pelosi a copy of the book “Catholicism for Dummies” in response to her pro-abortion-rights views. “I don’t think you’re going to see the pope regard climate change as an intrinsic evil. It’s just simply too broad.”

Francis’ immediate predecessor, Benedict XVI, went so far as to support Mexican bishops in their decision to excommunicate lawmakers who voted to liberalize abortion laws in Mexico City. Some U.S. bishops have promoted similar policies.

There is a difference, Donohue said, between official statements made in documents like the upcoming encyclical and off-the-cuff remarks like the ones Francis made during an interview with reporters last month aboard his papal airplane. It remains to be seen how this year’s encyclical could change that.

As for the Capitol Hill visit, Donohue predicted that the pope’s remarks this fall would be relatively conservative, though he might make more news in sideline interviews with reporters – as he has in the past, sometimes to the chagrin of Vatican communications officials.

“I don’t think he minds playing the role of a maverick,” he said.

Brian Burch, president of CatholicVote.org, said in an email that a Catholic politician would have to advocate environmental destruction for its own sake to be as out of touch with church teachings as a pro-abortion-rights Catholic Democrat. CatholicVote.org endorses lawmakers for their opposition to abortion and gay marriage, as well as conservative positions on issues like Obamacare and national security.

Asked about the climate positions of Catholic conservatives like Ryan and Rubio, Burch commended them for calling “for a careful balancing of the interests of workers, the economy and the environment in light of the ever-changing data, science and the associated theories.”

“Furthermore, both Ryan and Rubio likely have some reservations about what level of society is best suited to manage these difficult questions,” he said. “For example, must the United States submit to the judgments and control of international bodies that may violate our national sovereignty, or coerce Americans in other ways?”

Shaking people up

The Vatican has said it will release Francis’ encyclical on climate change early this year because it hopes to influence the Paris talks in December, which aim to produce a global agreement on curbing greenhouse gas emissions.

The pope has said he wants to spur U.N. negotiators to act “courageously.”

Carr of Georgetown University said the pope would be unlikely to weigh in on specifics of what the agreement should look like.

“He will make the case that there is a moral imperative to address the damage we’re doing to creation and the climate,” he said. “And that’s a very powerful message from one of the pre-eminent moral leaders in our world.”

While there are fault lines between the pontiff and the U.S. conservative faithful on global warming, the pope’s moral teachings do not fit neatly into either party’s platform. Francis has decried what he calls “the throwaway culture.”

Economic and social injustice, abortion, euthanasia and environmental degradation are all symptoms of that culture, he has said.

“He sees these things as linked, so he doesn’t fit the ideological or partisan categories of our debate,” Carr said.

Both Democrats and Republicans can be counted on to emphasize the parts of the pope’s message that agree with their views and to downplay the rest, he said.

Donohue said the pope’s “quixotic” style is intended to keep the faithful of all stripes from getting too comfortable.

“I think he understands that we need to shake people up out of their little paradigms, whether they be liberals or conservatives,” he said. “He has a little something for everybody.”

While Donohue himself said he thinks the human link to climate change is still an area of disagreement, he called the pope’s willingness to wade into controversy “refreshing.”

“And these Republicans are going to have to get over it,” Donohue said, “as some Democrats are going to have to get over it on some other things he says.”