WASHINGTON — A Republican lawmaker said he will boycott Pope Francis’ speech to Congress next week because of the possibility the pontiff will discuss his support for policies to fight climate change.

Three-term Rep. Paul Gosar of Arizona said that as a Roman Catholic, he initially was excited to learn of the pope’s visit to Washington and his address to Congress. But Gosar said he decided not to attend after he read media reports that the pope plans to devote much of the speech to advocating for what Gosar calls “flawed climate change policies.”

In a column Thursday on the conservative website townhall.com, Gosar wrote that he was appalled by a papal teaching document that “condemned anyone skeptical of the link between human activity and climate change.” He said that if the Pope stuck to standard Christian theology or spoke out with moral authority against violent Islam, “I would be there cheering him on.”

If the pope “urged the Western nations to rescue persecuted Christians in the Middle East, I would back him wholeheartedly,” Gosar added. “But when the pope chooses to act and talk like a leftist politician, then he can expect to be treated like one.”

As an elected official and a Catholic, Gosar said he has “a moral obligation and leadership responsibility to call out leaders, regardless of their titles, who ignore Christian persecution and fail to embrace opportunities to advocate for religious freedom and the sanctity of human life.”

No one knows exactly what Francis will say to Congress. But Vatican aides have said that throughout his U.S. trip, he will press his message on the environment, immigration and caring for the poor. The pope has called on government leaders worldwide to take bold action to address climate change and has said he hoped his teaching document, or encyclical, would help influence the United Nations climate talks at the end of the year.

The Vatican Secretary of State, Cardinal Pietro Parolin, told Vatican television Thursday that in his speeches to Congress and the UN the pope will emphasize the encyclical’s message on the need to protect the environment.

If Francis wants to devote his life to fighting climate change, Gosar said, he should do so in his personal time — not as pope. “To promote questionable science as Catholic dogma is ridiculous,” he said.

Gosar said he might reconsider the boycott if he were to receive “assurances” from the Vatican that the pope will focus his speech on religious tolerance and the sanctity of life, Gosar said.

“If there is one person that can talk about this in hell’s den — which is right here (in the Capitol) — that’s the pope,” Gosar said. “And if he’s not going to make that his concentrating message, I find it disheartening.”