The release on Thursday of Pope Francis’s new encyclical, Laudato Si' (Praised Be to You), has provided a rare moment of hope in the worldwide battle over climate change. The environmental movement’s powerful new ally appeals for a “new dialogue about how we are shaping the future of our planet.” He argues that we face “a global problem with grave implications,” and that fossil fuels “need to be progressively replaced without delay.”

Francis, the leader of 1.2 billion Catholics worldwide, has timed the document’s release to have the greatest possible impact on global policy: to influence negotiations at the United Nations Climate Change Conference in Paris later this year.

For many, the Pope’s message will not only propel the U.N. talks, but eclipse them. NASA climatologist Gavin Schmidt said the encyclical “is probably going to have a bigger impact than the Paris negotiations,” explaining in an email that Francis's “value judgments will likely count for more in terms of moving people to act (whether that is at an individual, community, state or federal level).” Senator Sheldon Whitehouse of Rhode Island told National Journal, “I think it will change the debate by lending a moral aspect to it, by bringing discussions into parishes and Catholic schools and universities and societies across the country.” Andrew Freedman, a climate reporter for Mashable, tweeted:

The Pope’s message is a game-changer, they argue, because he fills a key, missing role in the climate debate—the moral case for why people should care. And Francis acknowledges as much: “many efforts to seek concrete solutions to the environmental crisis have proved ineffective, not only because of powerful opposition but also because of a more general lack of interest. Obstructionist attitudes, even on the part of believers, can range from denial of the problem to indifference, nonchalant resignation or blind confidence in technical solutions. We require a new and universal solidarity.”

That the Vatican is throwing its weight behind the climate change movement is certainly exciting compared to the tedious deliberations of the U.N., which is collecting countries’ voluntary pledges to cut greenhouse gas emissions after 2020. Though the conference doesn't begin until November 30, it's already likely that the world will fail to limit warming to 2 degrees Celsius. So if the Pope can move public consciousness on the issue, the hopeful thinking goes, then politics and policy will eventually follow suit.

The real test is whether Francis can convince conservative politicians of the reality, and urgency, of climate change. The reaction so far, at least in the United States, suggests he can't. John Boehner, Paul Ryan, Jeb Bush, and Marco Rubio—all Catholic—have all dismissed Francis at some point.

Rubio has ignored the Pope on Cuba and Israel, arguing that “he’s not a political figure.” Ryan criticized his anti-poverty policy in 2013, saying, “The guy is from Argentina, they haven’t had real capitalism in Argentina.” And Bush has responded directly to the encyclical: “I hope I’m not going to get castigated for saying this by my priest back home, but I don’t get economic policy from my bishops or my cardinals or my pope.”

The implication is that Bush and company divine their policies from experts, not from religious figures. But if that were true, and Bush trusted economists’ advice on economic policy, he’d want a carbon tax for greenhouse gasses. The majority of economists, by the way, say that’s the best way to account for the externalities of pollution. Or if Bush were relying on expert opinion for his scientific policy, he would openly admit that expert science opinion says climate change is real and caused by humans. Bush has other interests in mind when he equivocates on climate change and when he dismisses policies like a carbon tax (he may be thinking of $7,500 per-person fly-fishing retreat he took with coal executives in May). There is no sign any of these politicians intend to listen to the Pope’s expert opinion on morality, either.

The United States is home to one of the world’s largest populations of Catholics, who are just as unlikely to be moved by the Pope’s argument. A recent Pew poll shows that over two-thirds of American Catholics view global warming as real, but only half attribute it to humans or as a serious problem. Pew notes the divide among Catholics falls along predictable partisan lines, which is another hint that it will take more than the Pope’s words to break this division. What it likely takes is leaders within the Republican party to speak out on climate change, but most of these leaders already align with climate change deniers. 

Climate advocates may argue that the Pope’s encyclical will have a broader impact on climate policy abroad. “We’re talking about a worldwide reaction to his speech, not just in the United States,” Representative Raul Grijalva, ranking member of the House Natural Resources Committee, said. “In the Third World and developing countries, that’s where the destruction is occurring. By being an encyclical, it becomes part of the agenda for the pope and the Catholic Church.”

Awareness in developing countries doesn’t do much good. Francis is addressing the same political stalemate that’s existed in climate politics for decades. The encyclical says, “developing countries, where the most important reserves of the biosphere are found, continue to fuel the development of richer countries at the cost of their own present and future.”

The way international agreements on climate change have long been structured, going back to the days of the Kyoto Protocol, is that rich nations should carry more of the burden for slashing pollution, since they are historically the biggest polluters. It’s a great approach, in theory, but has contributed to the decades of stalemate in agreements. The upcoming U.N. conference is different, we’re told, because for the first time every country is expected to contribute, whether it’s aid or emissions cuts. The traditional divide still makes progress difficult. India, one of the world’s largest polluters and growing, points to its new arrival as an industrial economy for why its government is reluctant to take more aggressive action.

Francis’s words hardly break the stalemate, and if the United States is any indication, his words aren’t powerful enough to dislodge politicians from their fossil fuel backers. Morals and faith may play a role in the global climate debate, but they're not enough to change policy.