Cogito, ergo sum.
I assume you weren't banking on radical skepticism here. If you take for granted that the knowledge granted by our senses is more or less correct (i.e. I can be sure I'm sitting down in front of a computer, I can be sure I'm blond, etc.), and ask about the meatier stuff, it gets more difficult.
I'm sure humanity will one day die out - though that's a given, isn't it? Worst case scenario, the universe ends. Unless you buy into the notion of ever-increasingly-long suspended animation to produce artificial immortality; but I'm not convinced. So I'm sure humanity will die out, and I'm sure I will one day die as well.
As for the rest, the difficult moral questions and questions of how to achieve things, I'm not 100% sure on any of that. I am 100% sure that there is a solution to most of the major problems society faces, but I don't know what they are, and I'm not convinced we'll find them in time (whether "in time" means "within 50 years" or "within 50,000 years").