More than 100 faith leaders have launched a campaign, timed to Pope Francis' visit to Philadelphia next week, urging Gov. Wolf to ban natural gas development.

The clergy, joined by a coalition of anti-drilling groups called Pennsylvanians Against Fracking, say their call to Wolf was inspired by the pope's recent encyclical urging Catholics to take action against climate change.

"Gov. Wolf, you have the opportunity and the obligation to act," the clergy said in a letter. "Shale gas development is not only putting us in an increasingly precarious position, it is also keeping us from making the necessary and urgent transition to clean, renewable energy."

The letter and advertising campaign is the second papal-themed anti-drilling action this week. Activists in Catholic clerical garb calling themselves the "Church of No Fracking" picketed Wednesday outside a conference sponsored by the Marcellus Shale Coalition.

David Spigelmyer, president of the trade group, said the industry took issue with claims that natural gas extraction was worsening greenhouse-gas emissions. Natural gas emits about half the carbon dioxide of coal, and by supplanting much coal-fired generation, the industry takes credit for U.S. greenhouse-gas reductions in the last decade.

But Spigelmyer was reluctant to engage in a religious debate. "I'll be honest with you," he said. "I don't want to get into a battle with the pope, because I'll lose that fight every day."