This story has been updated.

Admission to Pope Francis's Thursday address to a joint session of Congress is one of the toughest tickets in Washington in years. But one Catholic congressman says he will not be taking his seat for the speech in protest of the prelate's activism against climate change.

Rep. Paul Gosar (R-Ariz.) said in an op-ed published Friday on Townhall.com that he has "both 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."

"If the Pope stuck to standard Christian theology, I would be the first in line," he wrote. "If the Pope 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. But when the Pope chooses to act and talk like a leftist politician, then he can expect to be treated like one."

The Vatican has not indicated which themes and topics might be included in the papal address. But climate change is widely expected to be among them, given the publication earlier this year of "Laudato Si," Francis's encyclical on the environment, which calls climate change a "global problem with grave implications."

Cardinal Óscar Rodríguez, a close adviser to Francis who is archbishop of Tegucigalpa, Honduras, said in an April discussion at Georgetown University that care for the environment is likely to come up in the papal remarks.

Gosar cited reports on those comments as indicating that Francis "intends to focus the brunt of his speech on climate change." He describes himself as a "proud Catholic" and holds undergraduate and dental degrees from Creighton University, a Jesuit institution in Omaha.

A spokesman, Steven Smith, said Gosar attempted to schedule a meeting with Pope Francis or Vatican officials to share his concerns before the speech but was unable to do so.

Much as the public at large, American Catholics are in sharp, partisan disagreement about climate change. A recent Pew Research Center survey found over six in 10 Catholic Democrats saying global warming is occurring due to human activity and a similar number saying it is a very serious problem, compared with only about one-quarter of Catholic Republicans. Sixty-four percent of Catholics said it was “appropriate” for the pope to take a position on global warming in a July AP-NORC survey, though only 8 percent saw the issue as a religious issue.

Gosar is in his third term representing a swath of western Arizona. A practicing dentist before he entered politics, Gosar was elected in the tea party-fueled wave of 2010 and is considered among the House's most conservative members. He has been a frequent critic of the Environmental Protection Agency, recently calling for the impeachment of Administrator Gina McCarthy, and is an outspoken opponent of government intervention to address climate change.

"The earth’s climate has been changing since God created it, with or without man," he wrote Friday. "On that, we should all agree. ... If the Pope wants to devote his life to fighting climate change then he can do so in his personal time. But to promote questionable science as Catholic dogma is ridiculous."

Other Republicans, many of whom similarly skeptical about the human origins of climate change, have been less willing to challenge the pope. That includes House Speaker John A. Boehner, a devout Catholic who invited Francis to address Congress and said in July that he was "not about to get into an argument" with him. A Boehner spokeswoman declined to comment on Gosar's announcement.

The leader of one progressive Catholic group said Gosar's decision was "extremely disappointing" and that he "disrespected his Catholic Church and millions of Catholics throughout the United States with his decision to boycott Pope Francis."

"Contrary to Congressman Gosar's claim, Francis's call to care for God's creation doesn't diminish in any capacity his respect for all human life and his defense of persecuted Christians," said Christopher J. Hale, executive director of Catholics in Alliance for the Common Good. "We pray that he changes his mind and listens with an open heart to the inspiring leader of our Catholic Church."

Polling analyst Scott Clement contributed to this report.