Roger Pielke Jr. writes that it has not yet been proven or disproven that any part of the increase in flooding damage in recent decades up to the present is due to climate change up to the present. It took me a little while to figure that out from his post, but I'm pretty sure I've got it right.
I'm somewhat less interested in that proposition and more interested in what will happen in the future, as in the title I've written to this post. Now, the title to this post would be misleading if all that science told us was that only very small percentages of the global population will suffer from increased damaging floods. Similarly, it would be misleading if someone attacked the title's accuracy only because the science was unclear as to what will happen in some small areas.
The reason why global warming will clearly cause flooding is that sea level rise will exacerbate damaging, precipitation-induced, river flooding in and near coastal areas. That's a reasonable, general statement about flooding giving how much of the world population lives near sea level.
This site gives a range for the predicted sea level rise, but it centers around a half-meter rise. That may not sound like much, but it will result in significantly greater damage for areas that would have already been flooded, and a larger total area that is flooded. Even areas substantially upstream could suffer worse floods. Flood control structures might choose to not release enough water to prevent upstream floods, because of the impact it would have on severe flooding downstream near sea level.
This ignores the additional possibility that warmer temperatures will result in more intense storm events - I have no idea how good the science is for that proposition, but that sea level will rise from global warming is a very strong conclusion.
Long story shortened: global warming will cause flooding. If one has time to say more, the flooding will clearly happen in and near coastal areas where the world's population lives, and may happen further inland as well.
(BTW, I self-plagiarized some of this post from comments I wrote to Roger's post.)
key: science, global warming