I see Northamptonshire will disappear (that's where I'm originally from). Can't say that will be any great loss. But I wonder why places like Llangybi are on the map, and Lampeter not? Neither is huge, but Llangybi is literally half a dozen houses and a couple of sheep.
I suspect that the mapmakers used isometric topographic maps and selected a level at which they postulated the world water level will be, which determined the shorelines. I think they put some (arbitrary?) locations on the map as reference points.
Remember, though, if things happen this way, take note at what is being inundated by the rising waters. It's the 'lowlands'. And what is located in most of the 'lowlands'? Arable land. Land which can be farmed to produce food. More people, thanks to the population explosion, and less arable land to raise less food to feed more people. Not to mention destruction of much of the capital of advanced societies and dislocation of communities and means to support those communities.
I think the mapmakers have exaggerated the predicted sea level rise by a factor of 50 to 125. They assume a rise of 100 metres (see link) but other sources suggest a rise of from 0.8 to 2.0 metres (see National Geographic).
I agree that 100 meters, particularly by 2100, is highly unlikely.
This article states that if all ice melted, the world sea level would rise about 70 meters, so we're not talking 'factors of 50 to 125', whatever that means. This particular scientist seems to think that inundation will be at only 70% of the levels assumed on the included map.
But, as I noted, I hardly think that any such a melt level is likely by 2100....But hey, we're ahead of schedule already.
Yes, eventually all life will die out but I'm talking about the era dominated by global warming, that is the next 10,000 years. Global warming, by itself, will not cause Homo sapiens to become extinct.
The human race will survive, it is very resilient, but not in its current form. The Doomsday scenario, where all life on earth dies out won't happen.
As George Carlin was fond of noting...."What's all this worry about the planet? The planet is going to be fine. We're fucked; but the planet will go on just fine without us."
Will humanity survive the coming global changes? Perhaps. But remember 'survive' is something of a baseline term. We could, given the Mathusian postulation, survive in a state of perpetual misery, which is what population dynamics would suggest. At this point, though, our species seems to have overshot its 'survivability' limits and a major die-off event portends. We have overextended on our carrying capacity and the resource base will collapse....that will not be fun. Indeed, it will be horrific beyond imaging. But, it need not mean the end of the species.