Taking a forceful step into the international debate over how best to address global warming, Pope Francis issued the Catholic Church’s first-ever encyclical exclusively on the environment Thursday morning, making a sweeping moral and scientific case for addressing what he acknowledged as human-caused climate change that he said threatens “all of us,” but especially the poor.

"Climate change is a global problem with grave implications: environmental, social, economic, political and for the distribution of goods," the encyclical declares. "It represents one of the principal challenges facing humanity in our day. Its worst impact will probably be felt by developing countries in coming decades."

The 184-page letter, in the works for more than a year, was sent to bishops around the world. But it was addressed to “all humanity,” not just the faith’s more than 1.2 billion Roman Catholics.

Leaked Tuesday by an Italian magazine that broke a Vatican embargo on publishing the letter ahead of its official roll-out Thursday, some environmental advocates feared its potential impact had been blunted -- perhaps "sabotaged," in the words of a Vatican official, by conservatives within the Church opposed to Francis' more progressive stances on birth control, gay marriage and now climate change. The encyclical comes ahead of a U.N. meeting in New York City in September and a potentially historic climate summit in Paris this winter, something climate scientists and environmentalists alike say they hope will spur policymakers to action: specifically, an accord to reduce the heat-trapping carbon emissions causing climate change.

"We must now seize this narrow window of opportunity and embark on ambitious actions and policies to help protect people and the environment," World Bank Group president Jim Yong Kim said in a statement. "This is an urgent, moral, and ethical task for all of us.”

The Franciscan Action Network, an advocacy group that's called for action on immigration reform, the environment and human trafficking, said the encyclical only strengthens the legacy Francis began to establish as soon as he assumed office, one founded on a focus on the world's poor and gaps between the powerful and the vulnerable.

"From the start of his papacy when he chose the name Francis, to today, starting his encyclical by quoting the Canticle of Creatures, it's clear that the Pope believes that the environment is one of the most pressing issues of our day," the group said in a statement. "We must work together to find solutions to this problem."

Like a thesis or a Supreme Court brief, the encyclical – translated into five languages – cited both scripture and studies and reports by the U.N. Intergovernmental Panel on Climate Change and the Pontifical Academy of Sciences, a 400-year-old body of scientists funded by the Vatican. The prose is at once technical and elegaic, with references to both "bioaccumulation" and Earth as a “sister” that's been made a victim of "plunder.” The letter warns of the dangers of nonstop development, excess waste and, most urgently, runaway climate change.

“It is true that there are other factors (such as volcanic activity, variations in the earth’s orbit and axis, the solar cycle), yet a number of scientific studies indicate that most global warming in recent decades is due to the great concentration of greenhouse gases (carbon dioxide, methane, nitrogen oxides and others) released mainly as a result of human activity," Francis said. “This century may well witness extraordinary climate change and an unprecedented destruction of ecosystems, with serious consequences for all of us."

It also voices skepticism of so-called carbon cap-and-trade programs, which allow heavy polluters, such as coal-fired power plants, to buy credits from cleaner industries, like solar, wind or natural gas plants. While in place in the European Union and parts of the United States, Francis argues these programs do not "allow for the radical change which present circumstances require" for reducing carbon emissions.

"Rather, it may simply become a ploy which permits maintaining the excessive consumption of some countries and sectors," the pope wrote.

Even before the letter’s release, Republican lawmakers and presidential candidates dismissed the pope’s warnings.

“Everyone is going to ride the pope now. Isn’t that wonderful,” Oklahoma Republican James Inhofe, chairman of the Senate Environment and Public Works Committee and author of a book describing manmade climate change a “hoax,” said last week. “The pope ought to stay with his job, and we’ll stay with ours.”

Francis earned a degree as a chemical technician and, among other jobs, worked in a chemical laboratory before entering the seminary. Nonetheless, former Florida Governor and presidential candidate Jeb Bush, who is Catholic, was similarly unimpressed.

“I hope I’m not going to get castigated for saying this by my priest back home,” he said, “but I don’t get economic policy from my bishops or my cardinals or my pope.”

Catholicism, he added, “ought to be about making us better as people, less about things [that] end up getting into the political realm.”

Nevertheless, environmental groups and liberal lawmakers, including Vermont Senator and Democratic presidential candidate Bernie Sanders, voiced strong support for the encyclical and the action they hope it will inspire.

“Pope Francis’ powerful message on climate change should change the debate around the world and become a catalyst for the bold actions needed to reverse global warming," Sanders, an independent who tends to side with Democrats in the Senate, said in a statement.