This is probably a little off topic, but it can all melt in a few hours with one decent sized asteroid. This happened before in Greenland. [1] Geologists have confirmed the impact that melted all the ice due to the existence of billions of microscopic diamonds in the crater. My question is, are we monitoring enough of space to know if a big rock is coming and what will people do?

[1] - https://www.sciencemag.org/news/2018/11/massive-crater-under...

If an asteroid of sufficient size were to strike Greenland, I think sea levels rising would be pretty far down the “this is definitely going to kill us all” list.

Absolutely. I believe it was estimated that asteroid was equivalent to something like 3000+ nuclear bombs all detonating at the same time.

In some places it will rise, in some others not: https://www.sciencemag.org/news/2016/02/how-melting-ice-shee...

What's the point of bringing this up? On average it is still going to be a tremendous rise.

It's important to mention the subtleties so we can best prepare, and so that naysayers can't point to localized sea level drops as proof that global warming is a hoax.

Paradoxically, Greenland's coastline is expected to see a relatively lower sea level in this scenario.

https://blogs.ei.columbia.edu/2020/02/05/greenland-rising-th...

That is 361.1 million km^2 * 7.2m = 2.6 × 10^18 liters. Or a cube of side length 137.5km of water.