What is happening in the Arctic is now beyond words, so here are the pictures

> Other than displacing a large number of people who live on coastlines, what's the big deal?

"Other than that, how did you enjoy the play, Mrs. Lincoln?"

The displacement of large numbers of people will cause immense strife. Just look at the nasty reaction to the relatively small migration away from the Syrian civil war.

The problem is basically that all the land near populated coastlines is already owned, and those owners are not going to be inclined to let millions of their neighbors move in without some compensation.

But if those neighbors' coastal property just got swallowed by the sea, they probably don't have many assets left to pay.

The Danish meteorological report I linked to explicitly states that the temperature spike was caused by a foehn-like wind, and that the same phenomenon has already been recorded at the same weather station in past years.

It does indeed have tags as part of the spec, in order to account for about 0.2% of websites per a study done in December 2005. See this comment for the link in the spec: https://news.ycombinator.com/item?id=16462230

Melting of the northern permafrost could release a large amount of mercury (estimated around 800 gigagrams). (https://news.ycombinator.com/item?id=16330219)

There is also worry of a positive feedback loop that could cause global warming to spiral out of control. (https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis)

As far as sea-level rises are concerned, the Arctic sea ice will probably be a net sea-level fall, except around the Equator. If all of the Greenland glaciers were to disappear, well then, we would see a sea-level rise, globally. But it would be distributed unevenly across the world. The higher levels would again be around the Equator with decreasing levels the further north or south of the Equator you go.

But to get even a 1/3 of the Greenland ice cover to melt requires an unimaginably large amount of energy to do so. I'd have more concerns about the devastation of that much energy on the atmosphere than I do about any trivial amount of ice melt and associated sea-level rise.

The planet is close to being a steady state system, that is the energy inflows from the day side is about equivalent to the energy outflows on the night side. This varies throughout the year due to various factors, including orbital position, solar energy output, climate factors like clouds, etc.

The required energy to get 1/3 of Greenland glacial melt is approximately about the amount of energy received by the Earth on a single day, without any of that energy being released on the night side. Due to the slow conductivity of water in both solid and liquid forms, the atmosphere would need to essentially hold all of that energy. Even over a hundred years, that would probably mean atmospheric temperatures that would probably kill most, if not all, life on the surface of the planet.

There has been one study (that I know of) that has looked at the retention of energy over a period of about 50 years and the conclusion was that only 2 to maybe 5% of the energy retained managed to get into ice-melt. So to get the required ice-melt energy needed, we would need, say, 20 to 25 days worth of solar input radiation to be fully retained within the atmosphere (no leakage back into space).

In addition, I somehow think that even a 5 or 10 degree Celsius temperature rise would lead quickly to a sharp fall in global temperatures and would the initiation of a global ice-age. Since the planet has an approximate coverage by oceans and sea ice of 70%, an average rise of 5 to 10 degrees would more than likely see a huge rise in cloud coverage and subsequent reflection of energy back out into space, followed by a subsequent rapid cooling of the globe.

Of course, these figures are dependent on common available information and could be wrong by some percentage. It's not hard to do your own calculations if you want to get some feel for what might be possible.