So most religious politicians pick and mix their supposed "divine" beliefs to back up their preconceived thoughts. Who'd have thunk it?
(And yes lefty religionists do this as well. It's a two way street. Still intensely amusing to see people like Sicoko Santorum suddenly lose his pious warbling when it comes in conflict with the donors)
Faith in climate change is not a doctrine of the Roman Catholic Church. If Francis publicly proclaimed his preference for Pepsi over Coca-Cola, Catholics would not be obliged to drink it.
But here's the thing. Frannie isn't just saying "oh it would be super nice if we built some solar panels 
" - he's making it out that Catholics have a moral imperative to fight Climate Change.
What makes that different from previous Catholic indictments to fight the scourge of abortion, which Jeb and Rick so stridently support?
The Catholic position on abortion was dogmatically and infallibly defined in Evangelium Vitae. We won't know if the new encyclical does the same for climate change until we can actually read it.
The Pope's authority to teach infallible doctrine ex cathedra only extends to issues of morality and faith but his statements about humanity's duty to protect the environment could be interpreted as a moral teaching and therefore one that binds Catholics. I think that this has always been a tacitly held belief by Catholics, though. I believe that Bush, Santorum etc. would only be in conflict with Church teaching if he publicly stated that the environment wasn't worth preserving.
The encyclical won't. It can't really and the reason is because the entire concept of global warming is fundamentally a scientific question. The pope will almost undoubtedly say that the scientific consensus is that global warming is real and cause by carbon emissions. We may go so far as to say that given this consensus we have a moral duty to act. But an infallible declaration of man-caused global warning would be a radical departure of the Catholic teachings on faith and reason, and that of science in general. The Catholic Church teaches that faith and reason both lead us to the truth, and that science and the faith are not contradictory. If the Pope were to start making dogmatic decrees about science the entire framework would become incredibly messed up. It will likely be similar to how it is sinful to drop an anvil on someone's head even though the Catholic Church makes no dogmatic declaration about the existence of gravity. I suspect the Pope will also have some language about how science must be open to debate etc etc. The leaked draft was 191 pages long so he'll probably say pretty much everything related to the topic consistent with his views on the social effects of global warming and the Catholic Church's teachings.
As for the quotes here, Jeb's is awful theology and Santorum's is coherent and reasonable.
