In his first official day on the presidential campaign trail, yesterday, Republican Jeb Bush, a Catholic, had sharp words on Pope Francis' decision to leap into the climate change debate, saying the pontiff should steer clear of political issues.

Bush said he was eager to read an encyclical the Vatican is set to release tomorrow on climate change, but will take it with a grain of salt, even as he called Francis an extraordinary leader.

"I hope I'm not going to get castigated for saying this by my priest back home," Bush said. "But I don't get my economic policy from my bishops or my cardinals or my pope."

Bush, a former Florida governor who converted to Catholicism 25 years ago, said religion "ought to be about making us better as people and less about things that end up getting into the political realm."

Francis, according to a leaked draft version of his encyclical, or a letter to bishops, says the world could see destruction of entire ecosystems this century without urgent action on climate change.

In the Italian version of the 192-page document, posted on Monday by the weekly magazine l'Espresso, the pope again backs scientists who say global warming is mostly man-made and says that developed countries have a particular responsibility to stem a trend that will hurt the poor the most.

Bush is not the only Republican presidential candidate to differ publicly with Pope Francis.

In January, after the pope said there was no need to procreate "like rabbits" in order to be a faithful Catholic, Rick Santorum, a former U.S. senator and also a Catholic who announced his bid for the Republican nomination in May, said that it was "sometimes very difficult to listen to the pope and some of the things he says off the cuff."

More than 70 percent of U.S. Catholics believe the planet is getting warmer, though only 47 percent attribute that warming to human causes, according to the Pew Research Center. The views of Catholics on the issue are similar to those of Americans overall.