Everybody who cares at least slightly knows this, and I am pretty sure author knows this too, he could have spared us the initial hyperbole. Analysis itself is good but not everything needs to read like dramatic novel.
If all the ice melted it would raise the oceans by something like 230 feet, so modern Vienna would still be above water at 495 – 1778 ft elevation.
Although some estimates suggest Earth loses 20 - 30 cubic kilometres of water to space annually. Plus whatever water is bound up in mineralisation annually.
450 million cubic kilometres of water lost over a 15 million year period would lower ocean by something like … a bit?
The total volume of water on Earth is presently estimated to be around the 1.386 billion cubic kilometre mark.
The volume of a sphere increases to the cube of its radius … carry the 1 … nup, that’s to hard for me.
Beach front property in Vienna, at a guess?
https://www.usgs.gov/faqs/how-would-sea-level-change-if-all-...
https://www.ewash.org/how-much-water-disappears-from-earth-e...
https://science.nasa.gov/earth/earth-observatory/the-water-c...