Definitely a part of it. Another part is the intellectual understanding that this is probably going to happen, but the lack of an appropriate emotional reaction to imminent catastrophe. Aided by the sense that somehow it will be sorted at the last minute, everything will turn out OK, which I think is typical to human behaviour, an adaptation even to the gravest circumstances.
i don't know if this article has been posted in this thread already, but i found it quite interesting/moving at the time i read it:
http://www.lifeworth.com/deepadaptation.pdf
I suppose the issue for non-specialists is that they need to be convinced, or that the stakes for them need to be high enough. ie their lack of appropriate emotional reaction is based upon them being able to file it away, which could be for various reasons. One is, like you say, they think it will all be OK in the end, but another could be that they need to feel/see/experience something that does make them understand? And they haven't yet? As in, Jem Bendell, the author of the paper, looked at all the data, and made his decision. That same experience won'h happen for everyone who reads his paper though, they might need the information in a different way.
Yet another reason could be that for some people, they have more pressing issues to deal with day to day eg going to work, getting paid, surviving in debt or whatever.