lizrising: Good questions. Plants do throw off CO2 whenever they are not producing O. They make O when there is light, but at night they actually give off CO2. Obviously I'm not talking about dropping ice cubes into an already full glass of water, that would just be like adding more liquid water to the liquid water. My point about ice and water is mostly about how water contracts when it melts. Most (if not all) other substances will expand when going from solid to liquid. You are right about land based ice melting and adding it's volumn to ocean levels, but before it can even get there other factors are in play, such as evaporation, pooling into ponds and lakes, etc etc. I think maybe the scale of the ocean makes it difficult to believe it wouldn't be a big problem.. after all, it's a big ocean, and a very deep one.