The idea that THE POPE is speaking before congress about environmental policy and responsibility is huge. Separation of church and state is one of the ideas our country was founded upon, but religion often makes it into the decision caclculus of our elected officials. Try having a discussion examining our government's relationship to religion and how it impacts policy.
What has been the traditional role of the pope? How has it changed over time? Pope Francis is the first Jesuit Pope, what does that mean and where do the Jesuits come from? If you need the TEK, it's WH.5A.
The Pope is driving around in a Fiat for crying out loud. Climate change and the discussion of the human impact or lack there of is an extremely valuable discussion to have with your students.
Take the time now. You never know when you'll get another chance like this.