What is the volume of water that sea levels have risen by?
Since 1900, sea levels have risen about 8 inches…0.2 meters.The surface area of the world’s oceans is 360,000,000 square kilometers - or 360,000,000,000,000 square meters.So the additional volume is 0.2 x 360,000,000,000,000 which is 72,000,000,000,000 cubic meters.(This is a slightly inaccurate estimate because as the water level rises, it inundates some land - so the surface area is slightly increasing as well as the depth).Where did all of that water come from?Well, the increase in the actual amount of ocean water comes from things like the melting of glaciers and runoff from the antarctic continent. (Note that the melting of things that float - icebergs, the antarctic ice shelves and the north pole - don’t contribute to sea level rise.)But that’s not the real reason for the problem.As we warm up the planet, the water expands. The average depth of the ocean is around 3,700 meters - so it only has to expand by the tiniest percentage to produce an 0.2 meter increase in depth.The scary thing is that air temperatures take a while to influence water temperatures at great depths - so we may push the air temperature up and not notice much effect on the oceans for a long time - but sooner or later, the ocean will rise in temperature by the same amount as the air - and then it’ll rise by a MUCH larger amount than you’d think by watching the present day sea level rise.
Will the denialists help coin the next laughing stock statement of history?
Maybe, but they seem more likely to be remembered like the "experts" who testified that there was no link between smoking and cancer, or the newspaper that showed Titanic arriving joyously at New York. Climate science deniers don't really believe in anything as concrete as a flat earth or an Earth-centered universe. The reasons for climate science denial are instead a shifting grab bag of contradictory fictions, half-truths, deceptions, and distracting irrelevancies. A closer analogy may be Holocaust denial. Its deniers offer no consistent alternative history, just a series of endless circular claims that it couldn't have happened (despite what 99% of scholars in European history say), because it is (1) just an Israeli myth because Auschwitz was reconstructed, and thus never existed, or (2) it existed but was only a work camp, because how could you possibly cremate so many millions of bodies, or (3) Jews died there, but only of natural causes, or (4) some Nazis lied afterwards, therefore there was no mass killing, or (5) sure, the Nazis deliberately killed people in the camps, but Stalin killed more people, so the Holocaust must be just an Israeli plot; look at all those reparations Israel got.