Now, that is a question, different from the general ones, but still has some Physics in it and I really appreciate you to link the happenings with Science and reasoning, as it is good exercise for brain and also makes studies interesting. However for all of your Questions, you need some Geographical knowledge apart from Physics. 1) First of all, it is somewhat wrong to assume that there is little land base for huge masses of ice. Actually, what you are talking about are glaciers and in some cases, frozen water bodies. Most of the land covered by snow are in the Arctic Circle and the Antarctica. The Arctic circle includes many land masses with snow. And, Antarctica has about 14 million sq. km of ice covered region(more than the total area of India). The glaciers do not increase the water level of the Ocean, that's correct, but the ice from the land masses do increase the level, as they are present on the land and not submerged in water. Apart from the polar region land, ice is also present on various high peak mountains, from where many perennial rivers are continuously flowing. Global Warming increases the temperature due to which there is dramatic changes in seasons and the water bodies don't even freeze to maximum extent. That has caused near extinction of various species of Flora and Fauna, which is not good. 2) The vacuum that exists in space already rules out the heat transfer by modes of Conduction and convection. And the radiation effect is nullified by the large atmosphere surrounding the earth, which serves as a blanket and also the Greenhouse gases, which do not let the heat radiated by the earth to escape into outer space. 3) You can fill a container if you drop water, (drop by drop) in it everyday. Though its slow, it doesn't rule out the chance that the container is not filled. Same is the case here. The increase in water level may seem small to you, but just imagine ,that such a small increase in water level in the water bodies will amount to what if it is multiplied by the area over which an ocean expands. And that 'small' increase is not constant. It will keep on increasing till the phenomena of increasing does not stop. And with this pace, the already low lying land areas have the danger of 'extinction'. The Maldives are only about 2 m above Water level and would submerge if water level increases. Same is the danger with other land masses much above than water level, but excessive increase would lead to their disappearance. So don't take it lightly. A small problem is to be handled, when it is small only. A 15 to 21 cm rise is not in a bucket or a tank, its in an ocean. So if not heeded they might create a problem. Hope you find these answers satisfying. If any more doubt regarding these answers, you can post it here only. I will check it again in a week. And please keep posting such good Questions. It is really good for your concept development. Thanks.