The problem is that what’s rational for the group is not what’s rational for the individual.

In general, sure. But here, the disaster extends to all levels, which removes that argument, no?

Unfortunately not.

There are four scenarios to consider:

1. You do what’s best for the world, and the world is saved.

2. You ignore the big picture and the world is lost.

3. You do what’s best for the world, but the world is still lost because too many others didn’t do the same.

4. You ignore the big picture and the world is still saved because enough other people did the right thing.

Regardless of what happens, you’re personally better off ignoring the big picture and hoping that other people fix the problem. If disaster is coming, at least you’ll have a better life in the remaining time you have. If it’s not, why hurt yourself?

The exception to this is if your own personal actions make the difference to avoid disaster, i.e. that you go from scenario 2 to 3 above by changing what you personally do. But the chances of that being the case are extremely tiny. You need collective action to solve these problems.