I actually did a quick calculation, and my intuition was wrong. By one digit. But the digit mattes and confirms what climate change scientists say. The volume of all ocean water is an estimated 1335 million km3, with a surface area of 361 million km2. An expansion of 210 parts into a million (for one degree Celsius) makes for a volume of 280350 km3. Spread over a surface of 361 million km2, that makes for a rise of almost 80 cm. And ocean waters are warming with more than one degree Celsius. Combined with the sinking of cities that are not built on rock (like New York, for example), that makes for a bad scenario. :-) Please double-check the calculation. The point is: it is not because of the predicted Great Melt of Antarctica. The rise in sea water levels is or will be the result of the direct warming of oceans. I think climate change scientists should present more of such easy calculations. They are, apparently, more convincing that multi-variable weather or climate change models. :-)

This is a good point, and your back-of-envelope calculations are correct, but I'm not sure that the temperature will uniformly increase down to the bottom of the ocean. As far as I understand, the deep ocean (below 200m) does not sense that much what happens above. OK, let's increase this depth to 500m - still, we will be dealing with ~8 times smaller volume that should be considered as an expanding one, yielding ~10cm per degree of warming. Overall, I would be more worried by the increasing frequency of extreme meteorological events associated with global warming - it's easier to build even a 3m dam than to protect the whole area from hurricanes or tsunamis.

One extra point to add (my daughter made me attentive to this): the ice/snow on the North Pole and Greenland is not floating, and when that all melts, it will add 5 to 10 million km3 to the oceans, which makes for more than just a few cm. :-/ I added that element to the revised version (Preprint Some thoughts on climate change, resource constraints, and adaptation

Jean Louis Van Belle

Your daughter is correct. The main danger is from the land ice melting and entering the ocean. There is enough land ice on Greenland to raise sea level by approximately 7 m and enough in West Antarctica to raise sea level by another 5 m. 12 m is ~40 feet. Which port cities will survive that? East Antarctica has an additional 50 m of ice but it is thought that it will not melt any time soon. However, the Antarctic ice first formed when CO2 levels dropped below 600 ppm.

(Mark Pagani, Matthew Huber, Zhonghui Liu, Steven M. Bohaty, Jorijntje Henderiks, Willem Sijp, Srinath Krishnan, Robert M. Deconto. The Role of Carbon Dioxide During the Onset of Antarctic Glaciation. Science, 2 December 2011: Vol. 334 no. 6060 pp. 1261-1264 DOI: 10.1126/science.1203909)

CO2 is currently at 420 ppm and increasing at a rate of 3ppm per year so it will reach 600 ppm in 180/3 = sixty years time i.e. 2080 CE if the rise in CO2 remains constant.

Most of the ocean is at a temperature of 7 degs. C, but if it all warms to a surface temperature of 27 degs. C, then you will get a rise of 20 x your 80 cm per degree giving an additional rise of 16 m.

But it is not just sea level which is a problem caused by global warming. It is just that it is an obvious one.

I am still not sure and somewhat confused. As mentioned, ice sheets floating in the ocean do not add any rise in water level by melting: that is just physically impossible (see reference in original question). There is no netto addition of water when they melt.

Now, I just realized Antarctica is a proper continent, so most of its ice is land ice, while the North Pole is only sea ice. I do not know how I could mess that up, but I did. I guess it is because I looked at sites like this NOAA site - https://www.nesdis.noaa.gov/news/five-things-you-didnt-know-about-the-north-pole) which states: "the shrinking Arctic ice cap won’t contribute to sea level rise." [Even it adds that, of course, "it will influence normal weather patterns and the global climate."] Perhaps it's under influence of Trump's ideas that this extra sentence was added because - as mentioned - North Pole ice cannot add to net ocean water volumes, but the ice of continental Antarctica can or could!

So, this site on global ice volumes - https://www.antarcticglaciers.org/glaciers-and-climate/what-is-the-global-volume-of-land-ice-and-how-is-it-changing/ - is probably right when it says that the 'sea level equivalent' of Antarctica is enormous, but then how fast is it going to melt, really? Also, I do not see a clear distinction between the ice and land ice volume on Greenland on that site. Again, ice sheets on land (land ice) do add a netto volume of water and, therefore, must cause a rise in ocean water levels. However, the volume of land ice is not so enormous than the volumes of sea ice.

So, something inside of me keeps thinking we are talking inches or a few foot, rather than several meters. I am happy to see more detailed calculations - especially because this worries a few of my family members who live on the North Sea shore ! :-)

Well... Not sure. I looked at the Fort Denison study: it does indicate an 11.5 cm rise from mid-1915 to mid-2020, and so that must come from the (limited) melting of land ice so far, right? So if one or more tipping points are reached (once it is above zero degrees Celcius, ice does melt - slowly or rapidly), then it is going to go fast, I think. So, I conclude that a rise of - say - about 0.5 m over the next 100 years (rather than just 11.5 cm) is not unimagable. I updated the paper accordingly (Preprint Some thoughts on climate change, resource constraints, and adaptation

Yes. Of course. That I understand. The question here is whether or not rising CO2 levels in the atmosphere accelerate/decelerate such long-term cycles, and/or how CO2 concentration and long-term climatic cycles are or may be related. When looking at the past, I find this article interesting: https://newsroom.unsw.edu.au/news/science-technology/plunge-co2-put-freeze-antarctica. It shows Antarctica was actually formed when CO2 levels were low - because or additional to the cycles because of Sun-Earth distance or orientation of the poles and what have you... But thanks for adding this. Interesting ! Cheers - JL

Jean Louis Van Belle

There are three types of ice (sheets) in the Antarctic. Sea ice, ice shelves, and land ice sheets. The sea ice grows during the austral winter and retreats during the summer. Up until about 2018 the winter maximum had been increasing but now, and especially this year the maximum is much less than before. The ice shelves are also floating, and some of those floating parts break off to form ice bergs allowing more land ice to move onto the sea, so they do indirectly contribute to sea level rise. The third type is the ice sheets proper which are up to two miles thick, and feed the ice shelves. The ice shelves start at what is called the grounding line. As sea leve rises the grounding line retreats adding more ice to the sea and acting as a positive feedback which can lead to a tipping event with a sudden collapse of parts of the ice sheet.