The article talks not about "personal" optimism/pessimism, but about a social one. It compares an optimistic society with a pessimistic one. What this choice brings to a society?

> A very driven and confident pessimist might be much more motivated to find a solution for Climate Change, because he knows for sure otherwise Earth is Doomed.

Not so driven pessimists might tell that it is a waste of time, because Earth is Doomed.