This essay is addressed to members of the 9/11 Truth Movement, who believe that 9/11 attack was a false-flag operation, orchestrated by the Bush-Cheney administration so as to appear to be an attack by Muslims. Some members of this movement believe that, given the way in which people have been deceived by the official account of 9/11, we should suspect global warming theory is another false conspiracy theory. I argue that the conclusion that the official account of 9/11 is false provides no reason to suspect global warming theory to being another hoax. Written to challenge a view of some members of the 9/11 Truth Movement, this essay makes no effort to evaluate this movement's beliefs.