For some time now, as optimistic as I am about the long term future of mankind (or at least hopeful that we'll sort our shit out eventually), I have been fairly pessimistic about the medium term. Funnily enough, I've been hopeful about the short term as well - we're currently showing signs of beginning to get the immediate problems sorted. Medium term though, the big problem is population growth. Sometime in the next 40 years or so, we have to increase food production by 50%. Which is going to be ... hard. And it has been my understanding that the numbers of people we would have to feed would continue to increase in a geometric progression, or at least it would without some sort of effort to control the population.
So watching Hans Roslings latest talk engendered a significant amount of optimism. Yes, we're going to hit the 10 billion mark. It's not inevitable that we'll go significantly past that though. There's a number of countries where the birth rate is less than 2 children per woman. And it appears one of the bigger factors involved is education, specifically of women. Which is something that can be worked on, levels are far from perfect now, but it's a problem that can be tackled sensibly. A lot better than attempting to institute population controls.