We get back to the warming period of about one thousand years ago when Greenland was settled and they were growing grapes. It lasted for about four hundred years. Then it got real cold again, the settlers went back to Scandinavia (or froze to death), and grapes didn't grow there anymore.
What caused it to get that warm that far north, and why did it get cold again? I sincerely doubt humans driving SUVS and burning fossil fuels had anything to do with it.
But the whole northern hemisphere must have much warmer than now. So why didn't every plant and animal die? Why is there no record of cities on the sea coast flooding from sea water from all the melted ice?
Well, there is a record, sorta. You just have to be able to read it. The surface deposits where I grew up in the coastal plain of Maryland (in the tidewater) were the sort of mud found in swamps, complete with the limonite concretions and even preserved mud cracks in the clay. That area, now some 20 ft. above the mean High Tide mark, was once inundated, and for a considerable period. As for cities, nope, none present there, but if the water level was rising in a drowned river valley estuary, I'd have been further inland (especially away from swampy ground and the bugs that brings), and any habitation would have been further inland, too. (absence of advanced technology doesn't translate to stupid, after all).
While some towns and even cities may have been established during the warming period, that is a fairly short time to establish an extensive midden.
There should be beach deposits left from any stable period near then sea level, just as the beaches of Lake Agassiz were left as sand ridges in the Red River Valley of ND and MN. Inland from those, in the vicinity of any river channel (current or now abandoned) should be habitation sites.