A US activist group that has received funding from energy companies and the foundation controlled by conservative activist Charles Koch is trying to persuade the Vatican that “there is no global warming crisis” ahead of an environmental statement by Pope Francis this summer that is expected to call for strong action to combat climate change.

The Heartland Institute, a Chicago-based conservative thinktank that seeks to discredit established science on climate change, said it was sending a team of climate scientists to Rome “to inform Pope Francis of the truth about climate science”.

“Though Pope Francis’s heart is surely in the right place, he would do his flock and the world a disservice by putting his moral authority behind the United Nations’ unscientific agenda on the climate,” Joseph Bast, Heartland’s president, said in a statement.

Jim Lakely, a Heartland spokesman, said the thinktank was “working on” securing a meeting with the Vatican. “I think Catholics should examine the evidence for themselves, and understand that the Holy Father is an authority on spiritual matters, not scientific ones,” he said.

A 2013 survey of thousands of peer-reviewed papers in scientific journals found that 97.1% agreed that climate change is caused by human activity.

The lobbying push underlines the sensitivity surrounding Pope Francis’s highly anticipated encyclical on the environment, whose aim will be to frame the climate change issue as a moral imperative.

While it is not yet clear exactly what the encyclical will say, Pope Francis has been an outspoken advocate for action on the issue. In a speech in March, Cardinal Peter Turkson, who has played a key role in drafting the document, said Pope Francis was not attempting a “greening of the church”, but instead would emphasise that “for the Christian, to care for God’s ongoing work of creation is a duty, irrespective of the causes of climate change”.

The encyclical is expected to be released in June or July, and Pope Francis is expected to use a planned address before the United Nations in September to discuss the statement.

Any push by the Vatican on climate change could prove politically challenging for conservative Catholic lawmakers in the US who have denied the veracity of climate change science and fought against regulations to curb greenhouse gas emissions, including the Republican speaker of the House of Representatives, John Boehner.

The American Petroleum Institute, the biggest lobby group representing oil companies in Washington, declined to respond directly to questions from the Guardian about whether it was lobbying the Vatican on the issue.



But - in a sign of how energy groups and those who oppose greenhouse gas regulations are framing their argument to the Vatican - it said that “fossil fuels are a a vital tool for lifting people out of poverty around the world, which is something we’re committed to”.

Heartland has also targeted its argument to appeal to the pope’s views on poverty. It said in a press release that the world’s poor would “suffer horribly if reliable energy – the engine of prosperity and a better life – is made more expensive and less reliable by the decree of global planners”.

The group’s trip to Rome is designed to coincide with a workshop hosted by the Pontifical Academy of Sciences on Tuesday called Protect the Earth, Dignify Humanity, which will feature speeches by Ban Ki-moon, UN secretary-general, and Columbia University economist Jeffrey Sachs.

The Vatican declined to comment.

The Heartland Institute says it is a non-profit organisation that seeks to promote “free-market solutions” to social and economic problems. It does not disclose its donors, but says on its website that it has received a single donation of $25,000 in 2012 from the Charles G Koch Foundation, which was for the group’s work on health care policy. Charles Koch is the billionaire co-owner of Koch Industries, an oil refining and chemicals group, and is a major donor to Republicans causes and politicians.

Heartland said contributions from oil and tobacco groups have never amounted to more than 5% of its income.