What does rational optimism mean?

I read two blogs called Rational Optimist, one by Matt Ridley who is a fairly famous author that talks about environmentalism mostly and one by a much less famous American who talks about politics, religion and economics.  I feel like the descriptor rational optimist definitely applies to me but I wonder if most people would agree on what an optimist means in that context.  I have often described myself as an optimist and had people tell me that I was completely wrong as I often expect a very poor outcome from any given situation.  What I specifically aim for is being completely honest about what I know and what I do not know.  I know, for example, that the human experience has been consistently improving over known history.  We live longer, have more freedom and can connect with each other in so many more ways.  I also know that no matter what point in history you examine you find the same complaints about how society is getting worse, the younger generations are losing their morals, and things in general are headed for a reckoning.

That doesn't mean that nothing goes wrong of course.  We fight in pointless wars, we marginalize members of our society for their gender, sexual expression, skin colour, beliefs, culture, and ancestry, among other things.  Individuals commit all kinds of hideous crimes against others whether those crimes be as personal as a knifing or as sweeping as giving the order to 'kill them all.'  Despite all that things have gotten better and continue to get better.  There will be endless disappointments and steps backward but the trend over time for all of us is monotonically increasing and I expect it to stay that way.

I liken this progress to a drunkard stumbling home from the bar.  We are going to fall into ditches, trip over curbs, land in hedges and puke on our own shoes.  Despite the mess, embarrassment, and minor injuries though we are consistently weaving our way closer and closer to home and a nice comfy bed.  On any given moment we might see the drunkard doing something completely idiotic that obviously helps not at all and be tempted to despair but we must remember that slowly but surely progress is being made.  There will be endless people telling us that the drunkard will never arrive at their destination and countless examples of ridiculous exploits but we can look back at the weaving path the drunkard took and see the inevitable.

Bad things happen.  In any given situation something disastrous and terrible may come out of it.  There is no rational basis for being sure, for example, that we can get ourselves out of climate change, eliminate religion, or prevent any given war.  We can be quite sure that overall things will improve though, and in that way I think there is every reason to be a rational optimist.