06/10/2015 06:32 EDT | Updated 06/10/2016 05:59 EDT

Pope Francis might try to talk about climate change with Stephen Harper

Prime Minister Stephen Harper could get an earful on climate change when he meets with Pope Francis at the Vatican Thursday.

The pontiff is set to release one of his occasional "encyclicals" – a letter to one billion Catholics worldwide – with a focus on stewardship of the planet's environment. The June 18 message comes ahead of the United Nations climate conference in Paris this December that will aim to negotiate a new, post-2020 global climate agreement. 

Sources say the encyclical will include references to theology and the biblical links between man and the environment — driving home the message that the environment is a gift from God that Catholics are morally obliged to protect.

Catherine Clifford, a theology professor at St. Paul University in Ottawa, said the Pope will break new ground by addressing climate change.

"He's saying this is the issue — one of the important issues of our times and he wants to put it on the front burner for all Catholics around the world," Clifford said.

"The fact that any bishop of Rome wants to speak about this question in our time is really crucial."

The subject is perhaps not surprising since the Pope took his name from St. Francis of Assisi, the patron saint of animals and the environment.

'Fear of God' could push climate policy

The encyclical is also expected to make the point that poor people in the developed world should not have to bear the brunt of adapting to the effects of climate change, such as extreme weather.

"It's about poverty and justice," said Josianne Gauthier, who works with people in developing countries through Canadian Catholics for Development and Peace.

"It's impacting on the poorest of the world, who have had very little to do with the causes of climate change but who are suffering the highest impacts. So we're looking to Pope Francis to be that voice of the poorest, putting a human face on climate change."

The link between church groups and environmentalists was highlighted last fall during climate change protests in New York City.

Rev. Fletcher Harper, head of an interfaith coalition for the environment called GreenFaith, which is based in New Jersey, predicts the Pope could help dilute the political influence of climate change deniers — many part of the religious far right.

"One of the things that is really vital in terms of getting a good agreement in Paris and beyond is for politicians not only to feel that this is morally the right thing but also to have a little bit of the fear of God in them that if they don't act, there are going to be electoral repercussions," he said. 

Harper's meeting with the Pope comes days after he agreed to a G7 commitment to deep cuts in carbon emissions by 2050 — with an eventual stop in the use of fossil fuels by the end of the century.