EPA Pope Francis puts pressure on climate skeptics Conservatives in the U.S. pushed back on the pope’s message.

Pope Francis on Thursday backed the widespread scientific consensus that climate change is an urgent threat that is largely human-caused, and he called out skeptics for delaying actions to solve it — putting pressure on conservatives and candidates on the presidential campaign trail.

“Climate change is a global problem with grave implications: environmental, social, economic, political and for the distribution of goods. It represents one of the principal challenges facing humanity in our day,” Pope Francis wrote in an encyclical called “Laudato Si,” or “Be Praised.”

The encyclical, a document that outlines Catholic teachings, makes the case that tackling climate change is a moral issue, arguing that poor people suffer most from a warming planet and that everyone has a duty to be responsible stewards of the planet.

“Many of the poor live in areas particularly affected by phenomena related to warming, and their means of subsistence are largely dependent on natural reserves and ecosystemic services such as agriculture, fishing and forestry,” the pope wrote. “They have no other financial activities or resources which can enable them to adapt to climate change or to face natural disasters, and their access to social services and protection is very limited.”

The encyclical is already threatening to drive a wedge between Pope Francis and Catholic politicians like House Speaker John Boehner, former Florida Gov. Jeb Bush, New Jersey Gov. Chris Christie and Sen. Marco Rubio — who have all downplayed or expressed skepticism about climate science.

Following the leak of a draft of the encyclical earlier this week, conservatives pushed back on the pope’s message, arguing the pontiff should stay out of politically charged issues like climate change. But Bush, who unlike some candidates doesn’t dispute that climate change is occurring, appeared to soften his tone slightly this week.

Bush told reporters Tuesday that “I don’t get economic policy from my bishops or my cardinals or my pope.” But on Wednesday, he said, “I’m a Catholic and try to follow the teachings of the church,” and he focused his comments on avoiding policies that he said could hurt the U.S. economy.

In the encyclical, the pope appeared to directly challenge climate change skeptics. “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,” he said. “We require a new and universal solidarity.”

Environmental groups, U.S. Democrats and several Catholic officials were quick to praise the encyclical. Conservatives pushed back.

The encyclical is the second issued by Pope Francis since he became pope in March 2013, and it comes less than six months before delegates from nearly 200 nations arrive in Paris in hopes of clinching an agreement to reduce the greenhouse gases blamed for warming the planet. The pope, noting decades of failed international negotiations, said he was praying for success in reaching an “enforceable” agreement.

“We believers cannot fail to ask God for a positive outcome to the present discussions, so that future generations will not have to suffer the effects of our ill-advised delays,” he wrote.

The pope also used language from previous international environmental pacts to encourage negotiators to structure the agreement in such a way that wealthy and poor countries have different responsibilities for dealing with climate change.

“[S]ince the effects of climate change will be felt for a long time to come, even if stringent measures are taken now, some countries with scarce resources will require assistance in adapting to the effects already being produced, which affect their economies. In this context, there is a need for common and differentiated responsibilities,” he wrote.

And he bashed carbon markets, arguing that “the strategy of buying and selling ‘carbon credits’ can lead to a new form of speculation which would not help reduce the emission of polluting gases worldwide.”

The pope chastised powerful institutions and developed countries, arguing they are not doing enough to tackle climate change.

“Many of those who possess more resources and economic or political power seem mostly to be concerned with masking the problems or concealing their symptoms, simply making efforts to reduce some of the negative impacts of climate change,” he wrote.

Policies are needed “in the next few years” that will drastically cut greenhouse gas emissions, the pope said, recommending “substituting for fossil fuels and developing sources of renewable energy.”

The encyclical includes a sophisticated understanding of climate science. While acknowledging that the climate is a “complex system,” the pope points to a “very solid scientific consensus” that the planet is warming.

“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,” the pope wrote.

The pope said Wednesday at the Vatican that the encyclical is part of the Catholic church’s “social doctrine” and he encouraged “everyone to accept with open hearts this document.”

Environmental groups, Democrats and several Catholic officials were quick to praise the encyclical.

“Pope Francis’s guidance as a pastor and a teacher shines a light on the moral obligation we all share to address the climate crisis that transcends borders and politics,” Sierra Club Executive Director Michael Brune said in a statement. “This Encyclical underscores the need for climate action not just to protect our environment, but to protect humankind and the most vulnerable communities among us.”

Sen. Bernie Sanders, a presidential candidate, said in a statement that the encyclical “should change the debate around the world and become a catalyst for the bold actions needed to reverse global warming.”