"There's no such thing as settled science" is the last, best line of defense for those who don't believe in global warming, because it sounds so, well, scientific. It perhaps was most eloquently articulated by Texas Gov. Rick Perry in a 2011 Republican presidential debate.
"The idea that we would put Americans' economy at jeopardy based on scientific theory that's not settled yet to me is just nonsense," Perry explained. "Just because you have a group of scientists who stood up and said, here is the fact. Galileo got outvoted for a spell" [source: Saenz].
Besides the fact that this argument doesn't really refute any of the specifics of climate change theory, there's another problem: It's a debate in search of participants. Of the 4,014 scientific papers published between 1991 and 2011 that took a position on whether humans were causing global warming, for example, 97.1 percent endorsed the idea, while only 1.9 percent rejected it, and another 1 percent were uncertain [source: Cook et al.].
Additionally, just about every major scientific academy and professional organization in the world — some 200 of them — have adopted the position that the climate is changing and humans are largely responsible [source: Ca.gov]. That may not be absolute unanimity, but it's pretty close to it.