Hope is definitely not the same thing as optimism. It is not the conviction that something will turn out well but the certainty that something makes sense, regardless of how it turns out.This is a profoundly important distinction. We can be hopeful, even when pessimistic.
Endless debates about whether we "should" be optimistic or pessimistic are useless. They suggest no action. Bozo optimism is rampant these days, but we can (must) ignore such nonsense.
Otoh, hope (focusing on what makes sense) is all important. Once we have a proper plan we can start to make that plan come to pass. This will be far from easy: there are powerful forces committed to folly. The alternative is despair, the notion that no plan makes sense.
The paper, "A roadmap for rapid decarbonization", Science 24 March 2017, page 1269, is a perfect example of hope in action. It lays out a reasonable plan for dealing with global warming. It (rightly) ignores the myriad obstacles that such a reasonable plan will face. It focuses exclusively on what should happen, and ignores fruitless speculation about what will happen. This is a superior model for public policy and superb paper: powerful, concise and hard hitting.