Serendipity

1. Because their salaries depend on them not understanding. Applies to anyone working for the big oil companies, and apparently to a handful of “scientists” funded by them .
2. Because they cannot distinguish between pseudo-science and science. Seems to apply to some journalists, unfortunately.
3. Because the dynamics of complex systems are inherently hard to understand. Shown to be a major factor by the experiments Sterman did on MIT students.
4. Because all of the proposed solutions are incompatible with their ideology. Applies to most rightwing political parties, unfortunately.
5. Because scientists are poor communicators. Or, more precisely, few scientists can explain their work well to non-scientists.
6. Because they believe their god(s) would never let it happen. And there’s also a lunatic subgroup who welcome it as part of god’s plan (see rapture).
7. Because most of the key ideas are counter-intuitive. After all, a couple of degrees warmer is too small to feel.
8. Because the truth is just too scary. There seem to be plenty of people who accept that it’s happening, but don’t want to know any more because the whole thing is just too huge to think about.
9. Because they’ve learned that anyone who claims the end of the world is coming must be a crackpot. Although these days, I suspect this one is just a rhetorical device used by people in groups (1) and (4), rather than a genuine reason.
10. Because most of the people they talk to, and most of the stuff they read in the media also suffers from some of the above. Selective attention allows people to ignore anything that challenges their worldview.

But I fear the most insidious is because people think that changing their lightbulbs and sorting their recyclables counts as “doing your bit”. This idea allow you to stop thinking about it, and hence ignore just how serious a problem it really is.