Unless either extreme position (i.e. between "we've already lost and can't do a thing about it" on one end, and "climate change does not matter at all/can easily be solved with today's or tomorrow's technologies without any drastic impact to anyone/will fix itself/was a hoax..." on the other one) ends up being absolutely true in retrospect (which I consider quite unlikely), this might well be a game-theoretical problem:
If everybody ends up a defeatist, we really might end up losing primarily for that reason (due to most people, including decisionmakers, not even bothering doing forward-looking research, not conserving resources we have, accelerating resource depletion for the sake of "living life to its fullest" etc. as a result of that ideology), and vice versa.
In the book, one proposed solution of humanity to that meta-problem is a mind-altering machine that can instill an absolute belief in any chosen fact in everybody undergoing the procedure...
I seriously hope we won't ever look to any such dystopian measures, but I think the more important metaphor here is that defeatism, even if intellectually more honest and "true" (as far as that's an appropriate label for ideologies) in some contexts than an irrational believe that we can still succeed, can indeed become a self-fulfilling prophecy.
However there is a huge gap in humanity will emit less green house gases (GHG) because we switched to alternative energy sources and we emit less GHG because we mostly died off.