Could you elaborate as what about the melting of the Greenland Ice Sheet was concerning to Sir David King? Is it the mercury that is released or the rising sea levels it will cause or something else?
IIRC, when sheet melts, it will release a huge amount of fresh water into the salty Atlantic gulf stream and shut it down. The convection from top warm water sinking into the depth because of a salt concentration gradient will stop functioning.
Besides it's climate impact and heat transfer mechanism it will likely disturb the other ocean currents that are import for a stable climate as well.
Predicted results are huge acceleration of global warming as albedo is decreased and water absorption of GHG is decreased due toreduced mixing. Plus some rather big local climate changes earlier than that.
Easily getting us to the edge of what is livable even with advanced technology.
> Humans have experienced 120m sea level rise since the last ice age.
Human civilization didn’t, because human civilization didn’t exist at the last glacial maximum, and almost all of that rise was before human civilization existed. Low density nomadic hunter-gatherer existence is less disrupted by sea level change than settled agriculture and industry.
It's not about the survival of Humanity, but rather about global trade disruptions, mass-migrations, and massive property damage on a scale we've never seen. Humanity will be fine, but if it goes really bad then it will cause a lot of suffering and it may take centuries to recover.
And the third order effects will be further destabilization leading to more wars, which may go nuclear, and will all feed back into more environmental degradation.
It doesn't work like that. We don't get a new shoreline miles away.
What we get is every single existing ocean port city (which is a lot of the largest cities) being threatened by more frequent flooding. They're all right at sea level, because that's where you build port cities. Not all of these cities really depend on being ports any more, but that's how they became major population and business centers.
They don't just pick up and move something like that. There's no place you can say, "Oh, they're going to move New York over to X, so I'll buy land there now". Even if they did for some reason decide that it was so bad they had to abandon New York (or Charleston or San Francisco or lots of others), there's no one place that it goes. The whole human geography of it changes.
Just to add some international perspective to that: were talking multiple capitals, and entire countries being rendered uninhabitable. If ALL of the ice on Greenland melts (which luckily isn't likely here an now, but we're talking scenarios, right?) then over a billion people will end up being displaced.
While that's true, we didn't have as many major centers with permanent buildings set up. I'm looking for data, but I imagine that places like New York would be underwater, would they not?
Sea level rise is measured at 3.5mm/yr[1] as of 2016 so at current rate it will take 2000 years to hit 7m. NYC may be underwater but it would in all likelihood be as irrelevant to the future as Tyre or Carthage is today.
The concern is the acceleration of the sea level rise
"Whether it takes another 200 or 2000 years largely depends on how quickly the ice sheets melt. Even if global warming were to stop today, sea level would continue to rise."
Given the semi-permanent nature of changes at this point we should likely start talking in rates of change.
7 meter rise over 2 centuries can likely be managed in a reasonable manner via land taxation, resettlement, wall, and levy construction. 7 meter rise in 5 years would likely collapse most of the western world as major population centers find themselves unlivably under water.
Besides it's climate impact and heat transfer mechanism it will likely disturb the other ocean currents that are import for a stable climate as well.