The vikings stopped pillaging Europe, founded colonies in Iceland, Greenland and what is now Newfoundland, planted grape arbors, raised large herds of dairy cattle and experienced the good life until temperatures reverted to more or less normal patterns and ushered in the Little Ice Age.
There are no credible accounts of global cities being flooded or islands sinking beneath the oceans.
Not since the end of the last ice age anyway. What I want to know is, if they are soooo certain of impending climate flood doomage, where are all the dykes? Where are the sea walls? Surely there ought to be some serious flood abatement construction underway.