In summary, it goes like this: the sea levels rise due to melting ice, which puts so much water vapor into the atmosphere that the resulting dense cloud cover blocks sunlight, causing Nuclear Winter and resulting in Instant Ice Age, as seen in the accompanying D- disaster movie, The Day After Tomorrow, which was "based on real science".
“Back when I was young, around 11,000 or 13,000 BC — I forget which — we were coming out of an Ice Age, and we were going into a 1000 year freeze! We had floods! And hailstorms! Comets were whizzing paat us! You kids today have it easy!” [/very old codger]
What occurred in the middle is a phenomenon called "The Younger Dryas" ~ about 11,000 years ago, after everything had become warm and toasty and even forests were returning to the Midwest, it got nasty and cold again and glaciers built up almost overnight.
This diaster destroyed the Clovis culture in North America, and in some manner wiped out both the Giant Hairy Elephants, which was bad, and the Giant Nasty Saber toothed Tigers, which was good!
It lasted 1000 years.
Studies of nanoparticles left behind at the time indicate that a comet caused the problem one way or the other ~ either by dropping a giant hailstorm on Earth, or blasting holes in the remaining glacial sheet in Canada, or knocking SUVs off the road ~ something like that.
Whatever you learned as a child about the Ice Age(s) is bunk. There were at least 20 major cycles over the last couple of million years. The next one is certainly going to happen.