Key figures in the Republican Party verbally attacked Pope Francis as he is set to call for an ethical and economic revolution this week through an encyclical.

On Thursday, the pope is expected to release a letter about the increase in poverty and the prevention of climate change, reported the Guardian.

Pope Francis has been very vocal with his stand on climate change, saying it is mostly caused by human activity.

"I don't know if it [human activity] is the only cause, but mostly, in great part, it is man who has slapped nature in the face," said the pope. "We have, in a sense, taken over nature. I think we have exploited nature too much. Thanks be to God that today there are voices, so many people who are speaking out about it."

The encyclical, which is to be sent to 5,000 bishops and addressed to 1.2 billion Catholics worldwide, is expected to dwell on environmental issues such as the humans' role in exploitation of the world's resources, crossing the planet's natural boundaries, according to the Guardian.

"The pope ought to stay with his job, and we'll stay with ours," said James Inhofe, a climate change denier in the U.S. Congress and chairman of the Senate Environment and Public Works Committee. 

"The church has gotten it wrong a few times on science, and I think that we probably are better off leaving science to the scientists and focusing on what we're really good at, which is theology and morality," Catholic Republican presidential contender Rick Santorum told a Philadelphia radio station, according to the Huffington Post. "When we get involved with political and controversial scientific theories, I think the church is not as forceful and credible."

A majority of Republicans reject beliefs on the existence of climate change and counter regulations to cut emissions of greenhouse gases.